Weeds

Asiatic Hawksbeard

Q: What is the weed that has big leaves at the bottom; puts up a thin stalkHawksbeardwith a cluster of little yellow flowers at the top?  It is not a dandelion.  I see it every where now. 

A:  I believe you are describing Asiatic Hawksbeard, Youngia japonica.  This is classified as a cool season annual although it has been known to survive our winters.  It’s only means of reproduction is by seed so if you can pull it up before it produces a flower or use a weedeater, this weed is not too difficult to control.  It is common in Florida, found as far north as Pennsylvania and west to Louisiana.  It is a native of Southeast Asia. 

Black Medic

Q:  What is this horrible clover-like weed I am seeing everywhere, including my lawn.  The flower is a round, yellow cluster.  It runs similar to crabgrass but I think the leaves look like clover.  My wife says it is not clover, but I think it is.  We have a bet on this; the loser has to clean the kitchen for a week. So you get to decide - what is it? 

A:  I always hate to get into the middle of a husband and wife disagreement especially when cleaning the kitchen is the bet.Black Medic So, I will have to agree with you that the leaves are similar to clover but your wife is correct in that it is not clover. The weed you brought to the office is Black medic, Medicago lupulina. The name sounds ominous does it not? This plant originated from the Mediterranean. It has traditionally been used as a winter annual crop cover in the United States for corn, soybeans and small grains. This is the best time to get rid of the weed as the black seed clusters are now maturing. It is fairly easy to pull which is the best method of control, since it is an annual, and reproduces only by seed. Once the plant and seeds are removed then next years crop will be greatly diminished. Any chemical weed killer will be of little benefit as these are currently fully grown adult plants. The time to apply a chemical is when the weed is very small and before it has reached reproductive stages. This weed grows in the same type of environment as clover and they are often seen together. One other important fact, black medic can be an indication the lawn has too little nitrogen.

Beggarweed

Q I would like to know the scientific name of beggerweed which has 3 leaves, a purple flower and grows about 8 inches tall and how to control it.

A: I believe you are referring to the weed commonly called BeggarweedCreeping Beggarweed whose scientific name is Desmodium incanum. It is found throughout Florida, Texas, Mexico and countries further south. As a child, I remember spending many a day picking the Creeping Beggarweed seeds off my socks and the fur of my family pets. I always got the fun jobs when I was young. This is a perennial weed with a large taproot and many long extensively branched runners which roots at the nodes. The leaves contain 3 leaflets which vary in size but are generally elliptical and hairy. The stem is erect; flowers range in color from pink to deep rose but are often small and inconspicuous. The fruit forms with six or eight rounded segments which when ripened break off easily and attach to clothing and animal fur. Reproduction can occur by seed, stolons, and broken taproots. It is often found in turfgrass, open woods and disturbed areas. Use an herbicide for broadleaf weeds, but be careful to read the label and follow instructions. It is important the find an herbicide that will not damage your lawn grass.

Q:  We have an infestation of a weed (creeping beggarweed?), which has spread to the extent that removing by hand from the centipede grass is not an option. Do you have any suggestions as how it may be treated?

A: You are correct; this weed is probably creeping beggerweed, Desmodium incanum.  It is a perennial with a large taproot.  Its leaves are in groups of three and the flowers are light pink to rose.  It reproduces by seed, stolons and broken taproots so you need to use great effort to completely remove the root if you decide to dig it up.  You could use a pre-emergent next spring to help control it.  It is at the reproductive stage now and will be difficult to control with typical weed killers. One other thing, if you can locate the main stem, cut it close to the ground and immediately “paint” the cut stem with a Round-up type product.  Don't spray this chemical as it could easily drift to your grass and kill it.  Use a craft sponge paint brush, dipped in the chemical then apply it exactly where you want it to go. This weed is common throughout Florida and Texas.

 

Brazilian Pusley

Q:  Will you please identify this weed for me? 

A:  Thanks for bringing me a sample to the plant clinic.  The weed is called Brazilian pusley, Richardia brasiliensis. Brazil Pusley is an annual or perennial and looks similar to Florida pusley except it has a very deep, thick root. The thick root may be an excellent place for nematodes to live. Brazilian pusley has a cluster of small white flowers at the top.  In Florida, this plant occurs throughout the state on disturbed sites and roadsides, and in pastures and lawns. It is distributed in the southeastern United States, from southern Texas along the coastal plain to southeastern Virginia. This weed will bloom in almost any month that lacks frost. http://edis.ifas.ufl.edu/fw033

 

Burweed

Q:  What can you tell me about burweed?

A:  Burweed is also known as Carpet burweed or lawn burweed from the genus Soliva. BurweedYou mentioned being stuck when you tried to pull it up.  There is a small spine on the end of each of the seeds which is able to piece the skin and can be painful.  Burweed is a cool season annual and it has only one way to reproduce – by seed.  The good news is this weed is an annual which means if you pull it before the seeds fall to the ground you have killed any future plants.  We would suggest you remove the weeds by using a hoe rather than hand pulling.  Pre-emergent herbicides do not work well on this weed as competitors are wiped out allowing the burweed to thrive. 

Carpetweed

Q:  I let an area of my lawn empty for a few weeks as I was planning to re-sod.  Now I have this weed all over the place.  What is it? 

A:  Bringing in a fresh specimen during one of our plant clinics was beneficial. Carpetweed Often, when we describe weeds – they begin to all sound alike!  Your weed is called carpetweed or green carpetweed, Mollugo verticillata, which is a common summer annual with a small white flower.  The good news is this weed can only reproduce by seed so pulling it up before the seed has a chance to form and get into the ground is the ideal solution for controlling it.  The red seeds are very tiny and spread easily by wind or water. It generally is only a problem when lawn grass is getting established as it does not compete well with healthy lawns.  It is found throughout most of the United States as well as Canada and Mexico. 

Chamberbitter

Q:  I have a weed that appears to be taking over my St. Augustine lawn.  It seems to be born bearing seeds.  Can you tell me what it is?  Plus I was told to add lime to my yard to get control my weeds.  Will that really work? 

A:  The weed you brought to my office is called Chamberbitter (Phyllanthus urinaria L.) .Chamberbitter  You described it accurately when you said is is born with seeds.  If you check under the stems you will locate dozens of seeds.  It is classified as a summer annual and is found throughout Alabama, Georgia, Florida and Texas.  It is native to Asia and found commonly in the tropics.  I obtain a great deal of personal satisfaction from pulling these out by hand to ensure the seeds will be destroyed.  Regarding adding lime to control the weeds, we have no evidence this practice does anything to control weeds.  Lime is added to raise the soil pH and I would only advise you to add lime if a soil analysis indicated a true need.  Once lime is added and the soil pH is raised, it is very difficult to adjust or lower the pH.  The pH is an indicator of your soil acidity and determines how nutrients are absorbed through the root system to the plant.  If the pH is too high or too low your grass can develop problems.  Most St. Augustine grass prefers a pH of 6.5 so we will need to test your soil before we decide on the next course of action.  Remember to take care of your grass by mowing grass at highest height, water only as needed, fertilize with 15-0-15 or 16-4-8 two to four times a year, and avoid using weed and feed products. 

Clover

Q:  I have clover all over my yard.  It puts up a small white-pink flower.  I noticed the bees seem to love it.  What kind of clover is it? 
A:  White clover (Trifolium repens L.) is a cool-season legume.White Clover Although a perennial in many areas of the U.S., it frequently acts like an annual in Florida. White clover is one of the most nutritious forages available for milking cows. White clover grows best under cool temperatures and on fertile soils with excellent and sustained moisture holding capacity. It will disappear when temperatures begin to increase in the late spring and early summer.  Notice the slight white ring on the leaflet which makes it easy to identify.  White clover is an excellent source of nectar for bees foraging until the spring and summer flowers become available. 

Coral Ardisia

Q:  I have a short, dark green plant popping up in several places in my yard.  It has red berries hanging on it. Can you tell me what it is? 

A:   Thanks for bringing samples into the office of this plant as it makescoral ardesia it so much easier to identify.  The plant is called coral ardisia, Ardisia crenata. It is a non-native, invasive plant which is generally found in clumps and goes by the common name of Christmas berry. It used to be sold in nurseries but now Coral ardisia is classified as an invasive and I know of no legitimate nurseries who would sell it.  The “invasive” classification is the result of Coral ardisia finding its way into various wildlife areas replacing native food habitats.  Birds and raccoons disperse the berries into wooded areas. This plant easily grows back after fires and cutting it to the ground will not destroy it. The best way to manage it is to cut the stem and paint it immediately with a non-selective herbicide such as glyphosate.  It can be controlled by 2-4D but be sure you read the herbicide label before applying any of the chemicals mentioned. Removal of red berries would be beneficial to prevent the plant from spreading to other areas. Hand pulling smaller seedlings works well too. However, Coral ardisia has the potential to reach heights up to 6 feet; it is too difficult to pull tall specimens. We appreciate your interest in getting rid of this pesky, invasive plant from your landscape. The attached publication is from the Center of Aquatic and Invasive Plants, which contain more information and several photos of different stages to help identify the plant.   http://plants.ifas.ufl.edu/node/42

Creeping Cucumber

Q:  I found this weed growing in the soil I had delivered for my fall garden.  It looks like tiny watermelons but the leaf looks like a cucumber. 

A:   I have had three people bring this weed in to me within the last 2 weeks. Creeping CucumberI was fortunate in contacting the Duval County Commercial Extension Agent, Erin Harlow, and she was able to identify it for me immediately.  You most likely have the weed called creeping cucumber, Melothria pentula.  I found it interesting that most of the specimens of this weed  showed evidence of the disease powdery mildew on the leaves. The leaf does indeed look like a cucumber and the speckled, melon-like fruit is about the size of a pecan.  Creeping cucumber also produces a small yellow flower similar to cucurbit flower. Some of the educational sources I consulted about this plant stated the fruit was not for human consumption although some wildlife may use it for food.  There are some indications creeping cucumber may harbor the watermelon mosaic virus (WMV) and papaya ringspot virus (PRSV). It would therefore be important to remove the weed whenever it is located around vegetable or fruit gardens.  If the weed had the virus, it can easily be transmitted to other plants by one of the piercing/sucking insects such as aphids or whiteflies. This is a good example of why it is important to keep gardens weed free.

Cutleaf Evening Primrose

Q: Please identify this weed for me. 

A: I appreciate you bringing in a sample of the plant. It is difficult to identify plants andCutleaf Evening Primrose insects without having a good sample. Often flowering plants are classified as wildflowers or weeds depending on where they are growing. By definition, any plant out of place is considered a weed. Anyway, I said all that to let you know some people call your plant, Cutleaf Eveningprimrose, Oenothera laciniata Hill, a weed and others call it a wildflower. This is an herbaceous plant which can reach up to 2 feet tall and have a much larger spread. The leaves are heavily toothed and arranged alternately on the stems.  The flowers have four petals with a combined span just over inch. They are pale yellow sometimes pink. Blooms first appear in late spring and continue into early fall. Cutleaf Eveningprimrose is found in fields, fencerows and disturbed areas. This simple plant can be found in almost all of North America east of the Rocky Mountains and some areas west of the Rockies. Managing it will be difficult now that it is fully developed. Most herbicides work best when the weed is young (1 inch or smaller). You could apply a non-selective herbicide. But, be careful not to spray the product around other green plants as they will suffer the consequences (death!). Or you could just leave it alone and call it a wildflower!

Dichondra

Q:   I have this weed in my yard that looks similar to dollarweed but I know it is different.  Can you tell me what it is? 

A:   It was easy to identify this weed once you brought me in a sample. Dichondra Dichondra or Ponyfoot, Dichondra carolinensis, is a perennial plant that reproduces by seed and stolon.  In some areas of the country dichondra is used as a popular ground cover in place of grass.  Once established it grows just as well in full sun as shade.  It is not salt or cold tolerant and does not respond well to foot traffic or compacted soil.  Dichondra is often found living underneath the canopy of trees as it is protected from severe cold by the tree branches. This plant requires quite a bit of water and nitrogen to maintain good health.  I suspect you may be applying too much of both to your lawn, which is a common practice in Northeast Florida.  St. Augustinegrass grown in our area will often become stressed and weak after a few years of over fertilization and over watering.  This poor management practice often results in weeds growing heartily in the lawn’s place.  Remember to use 15-0-15 fertilizers on St. Augustingrass with at least 25% of the nitrogen in a slow release form during the months of March, May and September.  Use iron sulfate during the summer with as little nitrogen as possible.  It is best to water St. Augustinegrass on an “as needed” basis.  Water when the grass blade starts to slightly fold onto itself, which means you should set your irrigation system on manual.  Ideally, you should only water between the hours of 6am – 10am.  Keep your St. Augustinegrass at 3.5 – 4 inches high and never remove more than 1/3 of the blade at any mowing.  Never scalp or cut the lawn extremely short.  It is not advisable to add lime to the yard unless a soil analysis advises you to do so.  So how do you get rid of dichondra – maintain a healthy lawn by using best management practices of proper fertilization, irrigation and mowing.

Dodder Plant

Q:  What is this vine growing around my shrub? 
A:  Thank you for bringing it in, it made the identification much easier. Dodder VineYou have dodder plant, which belongs to the genus Cuscuta. There are more than 150 species of dodder plants worldwide. They are unusual plants because they do not possess leaves or roots and do not contain chlorophyll. This means dodder must obtain its nutrients from other plants therefore it is a parasite. It reproduces by seed only but it produces prolific amounts of seed. If left unchecked, it will totally take over large sections of plant material. The long, thread, vine-like structures are actually stems which wrap around the stems and trunks of other plants. The seeds have been known to survive in the ground as long as twenty years. Once they do germinate, if they do not attach quickly to other plant material they will wither and die. Mechanical removal works best when the plant population is small.  Often the host plant must also be removed in order to obtain complete control. Regular monitoring of the area should be done for the first few years to ensure the pest does not return. Pre-emergent chemical control works best using products containing the active ingredients: pronamide, trifluralin, or pendimethalin. Post-emergent products such as imazamox or paraquat will suppress the vine but not necessarily control it. The non-selective glyphosate will control dodder but will also kill the host plant. It is commonly known by other names such as vampire vine, love vine, Witches shoelaces or Devilguts, none of these names are very attractive which is appropriate for this plant.   

Doveweed

Q:  What the heck is this weed growing in my St. Augustinegrass? 

A:  I am glad you brought this weed into the office for me to identify because it is so similar Doveweedlooking to grass.  The weed you brought in is Doveweed, Murdannia nudiflora (L.) Brenan or Aneliema nudiflorum (L.) Kunth.  It is classified as an annual grass-like weed which makes it difficult to kill because it is a distant relative of turfgrasses such as St. Augustine.  It loves moist areas and tolerates shade very well.  Doveweed produces attractive, small purple or blue flowers but they are not very showy.  The good news is that is reproduces by seed only, which means you should use an herbicide (pre-emergent) that will discourage the seeds from germinating next year.  Pre-emergents, such as atrazine, should be used only twice a year (once in the spring and once in the fall).  This product is very potent and the label must be followed to avoid environmental damage.  Keep it away from water areas such as retention ponds and wells.  Nothing will kill the adult, seed producing plant now except a non-selective herbicide like Round-up.  Of course, if you use a non-selective herbicide you run the risk of killing any green plant it touches. You might consider pulling this weed since it is an annual.  The upside to pulling is you get rid of the adult and the future offspring all in one fell swoop. 

Q:  I have a terrible problem of doveweeds!  My yard guy sprayed a pre-emergent, but they still seem to be spreading.  What should I do? 
 A:  The bad news is doveweed is an annual, which means is produces huge numbers of seed.  The good news is doveweed has no other way to reproduce except by seed. Therefore, the best management of the weed is to get rid of it before it produces seed.  I know it is tedious but hand pulling is one of the best ways to control annuals combined with the pre-emergent your landscape maintenance professional applies.  Late summer is not the best time of year to apply weed killers, which the weeds apparently know because this it the peak time of year for weed production.  The only way to kill the adult weed during the summer is to use a non-selective weed killer, which will harm the grass or ornamental you are trying to save.  Consider giving your landscape maintenance professional another year to get the weeds under control by putting out an application of a pre-emergent in the fall of 2008 and spring of 2009.  These applications do not kill the adult weeds but they help prevent the seeds from germinating the following season.  Be patient – this is the best way to manage the little pests.  In addition, be sure you are putting your energy in caring for the lawn properly by mowing, watering and fertilizing using the appropriate amounts. 

Fireweed

Q:  This weed has come up in my flower pots and I would like to know what it is.  Can you identify it for me? 

A:   It is very difficult to identify weeds especially when the flowers are not present so IFireweed enlisted the help of some experts from the University of Florida.  The herbarium recognized some of the distinguishing characteristics then identified it as Fireweed or American Burnweed, Erechtites hieracifolia. The good news is this summer weed is an annual which means it can only reproduce by seed.  The bad news is annuals know they can only reproduce one way so they make the most of it by generating hundreds and sometimes even thousands of seeds. The white tuffs at the top of the stem are the seeds.  The white, fluffy portion of the seed makes it easy to for the seeds to be picked up by the wind and transferred to other areas where they can be spread.  This weed grows from two feet to over 6 feet tall and prefers to grow in full sun. Fireweed got its name because it is one of the first weeds to show up after a fire or disturbed areas. My advice is to pull the weed out of the flower pot before the seeds fully mature. Be careful to avoid pulling out the plants you want to keep.  If you feel you cannot remove the weed safely without destroying your plant, simply cut the weed close to the soil. This weed is so common, it can be found throughout most of the United States. 

 Florida Bellflower

Q: What is the name of this weed I found in my lawn grass?

Florida Bellflower A:  It looks like Florida Bellflower, Campanula floridana, which is native to FloridaIt is a perennial wildflower which makes it more difficult to control as it propagates by rhizomes and seeds. This wildflower can root at each node making it a proficient grower. Florida Bellflower is often found in over irrigated lawns, moist areas or poorly drained soil.  It has small purple flowers bloom year round. Florida Bellflower grows up to 12 inches tall and about 6 inches wide; tolerates full sun to partial shade. Typically found in cold hardiness zones 8-10.  Best management practice is to reduce water as it cannot tolerate dry areas. Chemical management can be done by applying atrazine in October and March to control seed production.  While I know you are not happy with the plant in your lawn, it might not be a bad plant for those areas near retention ponds to help reduce erosion. 

 

Florida Betony

Q:   What is this weed growing in my yard?  I brought in some fill dirt from an area in the woods and now I have a weed I cannot kill. 

A:   What you have is called Florida Betony, Stachys floridana, or Rattlesnake weed. Florida Betony The name for the genus, Stachys, is derived from the Greek word stachys, which means an ear of wheat or spike, as the flowers appear to be arranged in a similar way. The Latinized English species name floridana refers to the fact that it was first named from a Florida collection. This species was thought to be restricted (endemic) to Florida until the 1940s or 1950s. However, it is now found as far west as Texas and as far north as Virginia.  The stems of Florida betony are hairy, square and upright, and grow to between one and two feet tall. It leaves looks similar to the mint family and spreads just as quickly.  The trumpet-shaped flowers are white to pink and may have purple spots. The underground tuber is the reason for the common name "rattlesnake weed". It is segmented and white and resembles the rattle of a rattlesnake. Florida betony will grow in full sun to part shade and tolerates a wide variety of soil conditions including wet or dry. Florida betony reproduces primarily from tubers but also from seed and rhizomes. Throughout the winter months, it will grow and spread rapidly, especially in the loosened soil of landscape beds. If you are finding Florida Betony in the lawngrass your best management is to maintain a healthy, dense lawn by fertilizing, watering and mowing at the proper height and frequency. If it is growing in flower beds, remove as much of the root as possible, but small amounts of non-selective herbicide may be required for best management.  It is aggressive and will take over an area if not kept in check. 

Globe Sedge

Q: I have this weed all over my yard. Is it going to become sandspurs? 

A:  The weed you brought into the office is called Globe sedge Cyperus globulosus Aublet.Globe Sedge It is a perennial weed of turf found in moist and sandy habitats. The seedhead is comprised of several spikelets. Each spikelet consists of a long stalk with a round cluster of seeds perched on the end. Cylindric sedge and globe sedge seedheads are very similar in appearance. However, globe sedge seedheads are round, whereas cylindric sedge seedheads are oblong.It will never become a sandspur so you needn’t worry about that problem. It can tolerate any kind of soil conditions from sandy to bog-like. It prefers some shade especially in the afternoon. Globe sedge is difficult to control it once it matures to reproductive age. You can manage it now by using a non-selective herbicide. Consider applying a pre-emergent herbicide in the early spring of next year to better control this weed.  In addition, be sure you are irrigating your lawn appropriately. St. Augustinegrass prefers to be watered deeply but less often in order to build strong deep roots. Consider applying ¾ to 1 inch every time you irrigate, which ideally should be once every 5-7 days. Watch the grass blade. If it is full and green, it does not need to be watered. It would be a good idea to add a rain sensor to your in-ground irrigation system. A rain sensor will prevent your irrigation system from going on if we have received sufficient rain. 

Hairy Bittercress

Q:  Please identify this weed for me.  Thanks. 

 A:  The weed is hairy bittercress, Cardamine hirsute, and it typically is a winter annual but it will continue to grow in shaded, moist areas if it is not pulled or controlled.  It produces large numbers of seeds which have a high germination rate.  This, of course, means almost all the seeds become adult plants. It would be nice to have this kind of production rate on our vegetables and flowers!  The basal leaves somewhat resemble parsley and it has a small cluster of white flowers at the top.  Hairy bittercress often comes with contain plants so consider removing any weed from pots before you bring them home. I always return them back to the nursery and tell them I will not pay for plants I do not want! No one every laughs but better to dispose of them at the nursery then let them become a problem in your landscape.  There is another weed, very similar looking to the Hairy bittercress but its leaves are much smaller and it prefers dry soils. Neither weed is a bonus in the landscape.    

 

Heart-wing Sorrel

Q:  What is the weed with a reddish colored seed head which is showing up everywhere along the road sides right now. 
A:  I suspect you are referring to Heart-wing Sorrel, Rumex hastatulus, Heart-wing Sorrelwhich is in the buckwheat family.  It is a medium to tall annual weed found along many roadside and local pastures.  Leaves are basal, which means they grow close to the ground in a cluster. The species name “hastatulus” is Latin for spear-shaped which refers to the appearance of the leaves.  The flowers start out green and turn red when mature. If you look at the individual flowers closely, you will see they are heart-shaped from which it derives its common name.  It reproduces by seed only. This weed is common on sandy soil throughout the coastal plain of the southeastern United States. It occurs in Florida from the central part of the state northward into the southeastern United States to Texas, and northward through the Midwest to Montana and Illinois and through the Northeast to Massachusetts. The seeds are a common wild bird food. Oxalates in this plant can be poisonous by binding calcium in the blood. The sap can cause dermatitis in sensitive individuals.  http://edis.ifas.ufl.edu/fw036

Q:  Can you identify this weed for me.  I am seeing all over my pastures and open field areas.
 A:  This weed looks very similar to red sorrel which is a perennial. But this is actually a winter annual called heartwing sorrel, Rumex hastatulus.  If you look closely at the seed head you will see the seeds are slightly heart-shaped. Right now it is full of seeds so the best thing to do is mow it and collect the clippings then bag them and throw them away.  If you do it now, the crop of heartwing sorrel should be diminished next year.  This weed is found throughout most of the southern states.  It is edible for humans and great when a few are added to salads but it is somewhat sour which is where it gets its name - sorrel.   

 

Japanese Clover

Q:  Can you identify the weed that is all over my yard?

A: The weed you brought to the office is called Japanese clover, Lespedeza striata, or Common Lespedeza.  Japanese CloverIt is a prostrate, freely-branched summer annual.  The leaves are very tiny and they form a dense mat.  Japanese clover produces small purple or pink flowers, which are actually quite striking up close but the plant is basically too small to have much ornamental value.  Flowering occurs during July – October and it reproduces by seed only.  Common Lespedeza can found in fields, pastures, open woods, stream banks, roadsides, railroads, waste ground, disturbed and cultivated sites. This plant is utilized for horse and cattle forage.  It was brought to this country around 1904 and has spread rapidly.  It is difficult to kill a mature, seed producing plant once it has reached its maturity.  When I say maturity I mean it has reached the stage of its life cycle where it is capable of producing seed.  You might consider pulling it up prior to it releasing seeds and/or use a pre-emergent herbicide next spring to possibly prevent the dormant seeds from germinating.  Of course, our major focus should be taking care of the lawn so it is strong by proper fertilization, watering and mowing.  Check out the University of Florida website on residential St. Augustinegrass, http://edis.ifas.ufl.edu/LH010

Japanese Stiltgrass

Q:  What is this weed growing in my yard? 

Annual jewgrassA:  I believe the specimen you brought into the office is called Annual Jewgrass or Japanese Stiltgrass, Microstegium vimineum.  This warm season annual grass can be creeping or erect.  The good news:  it reproduces only by seed.  The bad news: it is difficult to manage and control in St. Augustinegrass since they are both grasses.  It prefers moist, shady areas which would keep the St. Augustinegrass thin and allow Japanese Stiltgrass to become better established. Your best plan of action now is to dig up what you can before it produces a seed head.  You could dab small amounts of glyphosate (Round-up) on the leaves (do not spray) and it will die within the week.  If this weed is too widespread then you must be diligent to spray a pre-emergent next summer to prevent the weed seeds from germinating

Q:  What is this grassy weed in my lawngrass? 

A:  Once you brought in a clump of the weed into the office it was easy to identify.  I have received two other such inquiries about the same weed, so it was fresh in my mind.  Annual Jewgrass, Microstegium vimineum, is a summer annual which prefers shaded areas.  It goes by other common names such as:  Japanese grass, Japanese stiltgrass. Nepalese browntop and Nepalgrass.  It is considered a noxious weed in Connecticut, Alabama and Massachusetts.   This weed is native to Asia and found in the United States from Ohio to Virginia southward.  It has no means of reproduction aside from seeds and this limitation makes it easier to control than perennial weeds.  Use a hoe, rake or remove by hand before it produces seeds then your chance of having this weed next year are greatly diminished.   Summer is not the best time of year to apply weed killer to lawn grasses as the herbicide may weaken or even kill the grass you wish to keep.  A pre-emergent herbicide could be used next spring to reduce the seed germination of this weed. 

Matchweed

Q:  Can you identify this weed I am finding in my lawn and how do I get rid of it?

A:  Thanks for bringing this weed to the office because describing it over the phone Matchweedmakes it difficult to identify.  The weed is commonly called Match Head or Matchweed, Phyla nodiflora.  It is a mat-forming perennial which reproduces by seed and stolons.  It is a common weed which is found from Pennsylvania south to Florida and as far west as California (even Hawaii).  This is not the best time of year to use any type of broadcast weed killer on the lawn as it may damage the lawn too.  I suggest you consider applying a Round-up type product but do not spray it on the weeds as it may drift to other parts of your lawn and kill it.  It would be better to use a craft sponge paint brush dipped in the pre-mixed glyphosate product and paint it directly on the weed leaves.  Be sure the sponge is not dripping to avoid the herbicide falling on plants or grass you do not want killed.  These sponges can be found in the paint section or craft center of your local hardware or department store.

Mushrooms

Q: My grass is newly sodded and with the recent rains I have noticed small, beige mushrooms growing in the grass. Should I do anything about them?

A: Often turfgrass is grown in heavy organic matter. As you have seen the mushrooms will pop up when rain fall is abundant or irrigation is increased in order to get the turfgrass established. The best method of control is to remove the mushrooms as soon as you see them. Place them in a plastic bag and throw them away. Try to harvest them before they completely open to avoid the spread of mushroom spores. Don’t get discouraged, you can eventually remove this mushroom by persistent hand picking. By the way, this method works for any mushroom even those you find in your mulch.

Oxalis

Q: I am not sure what I have in my lawn, but it is taking over and nothing is helping to get rid of it. The leaves are similar to clover. It has a root that looks like a white radish and blooms are purple. It has spread all over and is in large clumps choking out my grass. I pull all I can each year, but it is more than I can handle now. I live in Fernandina Beach. Hope you can help.

A: The weed you have is in the family oxalis, which if placed in a pot is often called shamrock.Oxalis  The flowers may be white, purple or yellow. The petals often resemble clover which causes people to confuse this plant with a common variety of clover. This particular lawn weed is difficult to control because it is classified as a perennial. Unlike annual weeds, which only reproduce by seed, perennials can reproduce by seed and vegetatively using other parts of the plant like the root, stolen or leaf. Pulling weeds by hand, which is my favorite pastime, often is unsuccessful with perennials because of their ability to reproduce in a variety of methods. Any portion of the weed left in the ground can produce a new plant, hence the reason why some weeds seem to be so stubborn and continue to return year after year. You will need to be persistent with this weed and consider using a weed killer for broadleaf weeds but be sure the product can be used on your type of grass. In addition, you should spot treat only the areas where the weeds exist, avoid spreading the product over the whole lawn. One other thing to consider is why weeds are coming up in your lawn. Healthy turfgrass should allow few weeds the opportunity to grow. If your turfgrass is St. Augustine remember to water it once every 5-7 days in the summer and once every 10-14 days in the winter. Water the lawn in the morning hours between 6am and 10am. Use a fertilizer product similar to 15-0-15. Look closely at the label and try to find a fertilizer product that has a portion of the nitrogen as slow release nitrogen. The first and last numbers on the label, which stand for nitrogen and potassium, should be balanced meaning the ratio should be 1:1 or at the most 2:1. Mow the lawn at the highest height. Fertilize in March and August or September. Avoid using weed and feed products. Use an iron sulfate product that contains only small amounts of nitrogen during the summer months.

Q:  What is wrong with my oxalis? 

 The bright, orange spots you see on the oxalis are caused by a fungus, Puccinia sorghi, which is a type of rust.  Generally, rust fungi must live on 2 or more plant hosts before they can complete their life cycle. They are quite complex even for such a simple organism. The rust found on the oxalis growing in your garden can be a real problem on corn, especially sweet corn.  The rust fungus lives through the winter on wood sorrel (oxalis) and when weather conditions are perfect, the spores of the rust are blown onto the corn. The ideal conditions for rust development are long, cool springs with temperatures ranging from 60° to 74°F plus high relative humidity. Usually rust does not cause enough damage to the oxalis to warrant any type of chemical control.  Although clipping the infected oxalis leaves would benefit any corn growers in the area and keep your oxalis looking neat and clean.  An application of a fungicide on the oxalis when leaves begin to develop next spring might also help. 

Poison Sumac

Q:  How can I tell if I have the poisonous kind of sumac? 

A:  The old adage, “three leaves let it be” does not apply to poison sumac, Poison SumacToxicodendron vernix.  Sumac leaves are classified as compound which means the petiole or stem arising from the bud has more than one leaf.  Poison sumac has 7 to 13 leaflets. The edges of the leaflets are smooth and not toothed. Many plants put out new leaves in the spring which are pale green in color but poison sumac leaflets are bright orange making them easy to spot.  These orange leaflets turn dark green and glossy as they mature. The underside of the leaflet becomes a pale green. The stem to which the leaflets attach is a red color which aides in identification once the poison sumac plant matures. Poison sumac can grow into a large shrub or even become almost tree-like. Take great care if they need to be removed by wearing long sleeves, pants and gloves. Once shrubs have been removed be cautious about exposing skin to any part of the plant.  Wash the clothing in a separate cycle from the rest of your laundry. Avoid exposure to burning brush as the smoke may irritate mouth, throat and lungs. I have attached a publication from the University of Florida/IFAS which provides more information on sumac, poison ivy and poison oak.  In addition, it provides an excellent drawing to help distinguish between other plants which may look similar to poison sumac.  For those of you who camp and hike, this publication might be an important document to keep in your backpack.  http://edis.ifas.ufl.edu/pdffiles/EP/EP22000.pdf  The attached photo is from Duke University.

Purple Nutsedge

Q:  I have a dark green weed growing all over my yard in large patches.  What is it? 

A:  Identifying weeds is often difficult because they change their growth habit after beingPurple Nutsedge mowed numerous times. Once you brought in a sample of this weed to the office with a seed head it was much easier to recognize. Your weed is one of the aquatic weeds commonly found in lawn grass called Purple nutsedge, Cyperus rotundus. It is a perennial, which means it has more than one growing season. Purple nutsedge can reproduce by seeds and underground rhizomes. The rhizomes enable the nutsedge to spread throughout the lawn. It is easy to become over confident when hand pulling these weeds. You yank out large lush green foliage with what appears to be a small white root structure thinking the weed has been destroyed. But you would be mistaken as this plant produces a tuber which must also be dug up or the plant will continue to be productive. Purple nutsedge, along with other common sedges such as Globe sedge or Yellow nutsedge, are difficult to manage. They also tell us a few other things about what may be occurring in your lawn. Sedges are aquatic weeds; this means they are indicators of the lawn receiving too much water. Therefore, reducing the amount of irrigation your lawn receives should be one of the cultural practices you adopt to better control their growth. Chemical (herbicide) application will not completely control these weeds. It is important to combine chemical control with cultural changes to best manage these weeds. In addition, please focus on keeping the lawn grass healthy as the stress of too much nitrogen combined with too much water weaken the grass and enable the weeds to reproduce quickly. Attached is a publication by the University of Florida regarding weed control in home landscapes to better assist you with managing weeds. We have a few more Horticulture Extension Plant Clinics scheduled for the fall (September 14, 28 and October 12, 26).  Bring us your sickly, tired and sad looking plant clippings to the Yulee Extension satellite office anytime from 10am - 2pm for advice on plant health care. This service is free to the public.   http://edis.ifas.ufl.edu/EP141

Red Spiderling

Q:  Can you identify this weed for me? 

A:  I am glad you brought in a sample which made it much easier for me to identify.  This is one of those plants which some people consider a wRed Spiderlingeed while others consider it a wildflower.  It is actually sold in some markets as an excellent choice for drought tolerant areas where there will be little water applied except rain. The plant is called Red spiderling, Boerhaavia coccinea.  It would make an excellent ground cover of those hot, dry parking lot medians.  It has a tiny reddish-burgundy flower which blooms in the late spring through the late summer.  I have a patch of it growing in the parking lot along the sidewalk at the Yulee satellite office.  I assumed the seed was propagated by a bird or wind.  You can imagine how harsh an environment the parking lot is – so this is indeed a tough plant.  Red spiderling can grow in full sun (like my parking lot) or partial shade.  Since it is a perennial, it can be propagated by seeds or rhizomes.

Sandburs

Q:  How do I get rid of sandburs in my yard? 

A:  I have received many questions this month about getting rid of weedsSandbur but the main problem has been the maturity of these weeds.  It is very difficult to kill adult, seed producing weeds in lawns.  The time for treating weeds is when the plant is very small, when it is easier to manage.  We have very few chemicals in our arsenal that will kill mature, reproductive weeds.  Ideally, we should be taking care of our lawns to reduce the number of weeds.  Proper care of lawns means strong healthy, nearly weed free lawns.  First, we should fertilize using 15-0-15, Nitrogen, Phosphorous, Potassium, respectively.  I know as Americans we feel if 15% Nitrogen is good, then 30% or 50% would be better – not necessarily.  Balance in everything, including lawn fertilizers. Fertilization should occur in March, May and September but NEVER in the summer months.   Irrigation is also essential in maintaining a healthy lawn.  Water lawns 6-10am about ¾ to 1 inch of water.  You will need to measure your sprinkler output.  Put out empty cat food or tuna fish cans (10-15) at a zone and run your system.  After 20 minutes, stick a ruler in the cans and measure your system’s output.  Run your sprinkler system until it reaches the ¾ to 1 inch so you know how long you need to water your lawn.  Do not add lime to the yard unless a soil test dictates the need for lime.  Now to get back to the sandbur problem; you could use a product called IMAGE but it must not be used in cold or hot weather and there are several don’t when using this product so please read and follow label directions.  But the best advice I can give you is to get rid of the seed heads (the stickers) on the weeds and apply a pre-emergent herbicide next year to prevent the seeds from germinating. 

Q:  I have sandspurs growing all over my yard.  How do I get rid of them?  The seeds are sticking on the fur of my dogs and when I pet them, I get stuck. 

A:  It is difficult to control any weed once it has reached the mature stages of producing flowers and seeds. Right now, (September ) removing the seed heads would be beneficial.  If you have a bag attachment to your mower you can gather the seed heads while mowing to reduce the chance they will produce more weeds next year. We do not recommend putting weed killer on lawns this time of year as the chemicals can stress or even kill the grass you wish to protect. The best management practice is to have a healthy lawn which means watering, mowing and fertilizing properly.  If you have areas where the grass had died then the weeds have an opportunity to thrive.  A pre-emergent herbicide can be used to reduce the likelihood of seeds from the sandspur to germinate next year.  This pre-emergent herbicide should be applied in the late winter or early spring. Look at the local garden centers for products used to control crabgrass and you will probably notice they are also used to manage sandspur. Please follow the directions on the label and apply at the appropriate time of year – late summer is too late.  Painting glyphosate (Round-up) on the green leaves of the sandspur now will destroy the plant too but not necessarily the seed.  Do not spray glyphosate as this chemical kills everything green – good grass as well.

Skunk Vine

Q:  What is the name of the vine-like weed growing in my turfgrass?  They are not difficult to pull up but it does smell unpleasant when it is disturbed.  I have never seen it flower.
Skunkvine

A:  After bringing me this specimen, it was easy to identify as skunk vine mostly because of the strong, unpleasant odor.  The plants are woody vines but it lacks thorns.  It does produce small, pale lilac flowers but they are so small they may not be conspicuous to you.  After it flowers it produces small, yellow-orange fruits.  Skunk vine and sewer vine are easily separated from one another by their fruits. Skunk vine has spherical fruits and the seed (diaspores) lack wings, whereas sewer vine has fruits that are laterally compressed and seeds that are conspicuously winged. The leaves of sewer vine are typically larger than those of skunk vine. The common English names of these plants relates to the odor of the leaves, which is due to the presence of sulfur compounds (Mabberley, 1997). The odor is another helpful characteristic used to identify these vines and it sets them from other plants.  For those of you who are literalists, I don’t think it really smells like skunk but it is nonetheless disagreeable.   In urban landscapes, this vine entwines branches of woody ornamental plants and also spreads horizontally through lawns, rooting at the nodes.  Skunk vine is a Category I Florida Exotic Pest Plant Council weed (Langeland and Craddock Burks, 1998), a listing that groups the plant with the most invasive weed species in Florida .

Spreading Dayflower

Q:  Can you identify this weed for me?  It has spread all over my flower beds. 

A:  It would have been somewhat difficult without the flower, but since you brought in a Spreading Dayflowernice section of the weed along with the blue flower I was able make a better determination of the plant. Spreading dayflower, Commelina diffusa, is commonly found in ditches and in low areas where water might accumulate. Of course, this weed can also be found in landscapes receiving too much water. This weed is particularly troublesome as it can carry the virus responsible for cucumber mosaic virus disease (CMV). This virus is found throughout the world and can infect many plants in the cucurbit family such as cucumber, squash, cantaloupe, tomatoes and peppers.  If you find creeping dayflower, it would be best to remove it or chemically treat it with an herbicide to keep it in check.  Aphids feeding on the dayflower can easily transmit the virus from the weed to the food crop. The symptoms can be mild in which there may be slight, twisted formations of leaves to whole plant stunting and reduction of fruit production.  In the landscape, the growth habit is somewhat similar to crabgrass but the stems are more succulent. It is often confused with doveweed but the blue flower makes it easy to distinguish.  The good news – it does not tolerate foot traffic, compacted soil or mowing well.  I think the best advice in a flower bed is to pull it manually and consider reducing the amount of water the flower bed receives

Thistle

Q:  Last year I had mulch delivered and now there are dozens of these tall weeds with yellow flowers.   My gardener has been pulling them up by the handfuls.  Can you tell me what they are?

 A:  I believe the weeds you brought to the office are sow thistles.  They are very tall with yellow flowers.  The perennial sow thistle is less spiny with a larger taproot than its annual cousin.  These are common lawn and landscape weeds found throughout most of the United States and Canada.  After the flower is spend it produces white, fluffy seeds that can easily be carried on the wind to other areas of your yard or even your neighbors’ yard.  Pulling them up now to get rid of the flower before it produces seed is a good strategy.  You might consider having your gardener put out a pre-emergent herbicide (providing he has the appropriate pesticide license) in the fall.  This will help prevent any seeds from germinating during the cooler winter and early spring seasons.

Q: What are the large weeds I have been seeing along the sides of the road near pastures and wooded areas  Some of the flowers are white and others are purple. 

A:  I think you might be referring to a thistle – possibly the yellow thistle - Yellow Thistlewhich can be about 2 – 2.5 feet tall. The leaves are long and have prickly spines along the margins or edges. I feel fairly certain it belongs to the genus Cirsium.  The flowers can be white, pink or purple. Yellow thistle is a biennial which means it puts up leaves the first season then flowers and seeds the second season. This plant is the larvae plant of the metal mark butterfly along with other plants in the aster family. The little metalmark, Calephelis virginiensis, is one of the tiniest butterflies but it is one of the South’s most beautiful. It is the only metalmark found in the southeastern coastal plain. The wings of the little metalmark butterfly vary in color from rusty orange to orange-brown and have metallic silver lines on the wings which is where the family gets the common name "metalmarks".  In the Connecticut, Pennsylvania and New Hampshire the yellow thistle is considered endangered and it is a threatened species in Rhode Island.  It is interesting the same plant is considered a noxious weed in Arkansas and Iowa. 

Three Seed Mercury Plant

Q:  What is the name of this weed? 

 A:  Thank you so much for bringing in a sample to the office during the plant clinic session. This is one of those plants where some people call it a weed and others call it a wildflower.  Acalypha virginica,Acalypha virginica Three-seed mercury plant, is a native annual and we here in Nassau County, Florida will begin to see it popping up in the wooded and wildlife areas in April.  It belongs to the spurge family although it does not always display the white, milky latex fluid in its stems commonly found in other spurge weeds and wildflowers.  The flowers of Three-seed mercury or Virginia copperleaf bloom in June and July but they are very, small and pale red in color - not very showy although some experts will disagree with me.  Three-seed mercury plants grow in partial shade and will not tolerate full, afternoon sun. This wildflower has been located in some wetland areas but I have found it in my yard and you know my landscape is not a wetland!  Three-seed mercury is a food source for large and small mammals as well as water and terrestrial birds. Three-seed mercury is commonly found from Canada to Florida and as far west as California. 

 

 

Vetch

Q:  I have a vine-like weed growing around the base of my shrubs.  It has a pretty pink-purple flower on it.  The leaf looks similar to a feather.  What can you tell me about it? 

A:  It was easy to identify once you brought me in a few clippings of this plant.  VetchI am certain it is Narrow-leaf vetch, Vicia sativa.  It is classified as an annual or short-lived perennial with reclining or climbing stems.  The plant has small tendrils which enable it to climb and wrap around limbs of small shrubs. The flower color is blue, purple or lavender. Narrow-leaf vetch is found worldwide in temperate regions and is native to Russia and much of Europe.

Weed Cloth

Q:  My husband and I are disagreeing about whether to add weed cloth to my tree and shrub beds.  What do you think?

A:  Well, first I am glad you did not tell me which side you were on, that makes it easier for me to answer your question without prejudice and I sure hope no money was riding on this.  Weed cloth does a fair job of keeping out weeds, but only a fair job.  The real “bad boy” perennial weeds such as nutsedge, Florida Betony and dollarweed are able to eventually find their way through this stuff.  The true weakness of this product is in what it doesn’t do.  It does not allow fertilizer to reach the root area effectively, which is where it needs to be applied.  It has a tendency to compact the underlying soil, which can be a real problem for trees and shrubs that need oxygen to develop strong roots.  Mulch is generally added on top of the weed cloth, which can compound the soil compaction problem.  In addition, weed cloth does not allow for the enrichment of soil if you add organic matter or use natural mulch such as pine straw or oak leaves.  So, the best answer is to use natural yard wastes such as leaf debris, pine straw, and grass clippings in your shrub and tree beds. If a weed pops up, pull it or paint it with an herbicide that contains glyphosate (Round-up) – don’t spray it.  If you spray Round-up the herbicide can drift to other plants you want to keep. Then take the money you would have spent on weed cloth and buy another plant.

Weeds

Q:  I want to avoid some of the weed problems I had this past summer.  You mentioned putting out a weed killer before the weeds come up.  When do I spray it? 

A:  We have had such a mild winter you might consider putting out a pre-emergent herbicide (weed killer) within the next few weeks. The general rule is you can apply the pre-emergent herbicide when our temperatures are between 65 and 75 degrees consistently for 4-5 days.  Right now, we are expecting cooler temperatures this weekend, so you might want to wait a little longer. A pre-emergent herbicide is used to keep the weed seeds from germinating or sprouting.  This type of chemical will not work on the mature weeds you are currently seeing now in your yard.  You may have to reapply in April or early May for some of those weeds which show up later in the summer such as Chamberbitter.  Please be sure you follow the directions on the pesticide label.  You do not want to cause damage to the lawn by applying too much of any herbicide.  One other important hint, be sure you are careful about what type of herbicide you use on Floratam, St. Augustinegrass.  Some of the herbicides can ultimately weaken, stress or even kill some varieties of St. Augustine.

Q:  I have sedges and dollarweed growing all over my yard.  In fact, I have very little St. Augustinegrass left.  What can I do? 

A:  Sedges and dollarweed are what we call indicator weeds, which means they can tell us something about the soil conditions of your yard.  These two weeds in particular tell us the area is wet or poorly drained.  You may consider trenching the area to allow water to drain better.  If drainage is not the problem then consider adjusting the amount of water you are putting on the lawn.  Ideally, you should let the grass tell you when to water.  If the blades of grass are fully open then watering is not necessary.  Water lawn grass once the blades begin to fold.  Irrigate in morning hours only (6-10am).  Water the lawn about once every 5-7 days in the summer and once every 10-14 days in the winter.  Irrigate ¾ to 1 inch each time as the grass responds best to deep watering.  Control is going to be difficult once dollarweed is well established; but management should include an application of an herbicide in the spring and fall only. However, chemical applications must be coupled with watering and fertilizing properly.  Avoid high nitrogen fertilizers and weed/feed products.  Fertilize in March, May and September only using a slow release fertilizer such as 15-0-15.

Q:  I have weeds coming up in my lawn.  What are they and how can I get rid of them? 

A:  This question has been coming into the office in large numbers.  The type of weed varies but most have been summer annuals such as Chamberbitter or crabgrass.  Summer is not the time of year to put out weed killers as they may do more damage to the lawn than the weeds.  If possible, hand pull the annuals before they produce seeds, which will stay in the ground until next summer.  By hand pulling the weeds, you not only get rid of the adult plant now but also next year’s plant.  If the weeds are in one main area you can paint them with a non-selective herbicide (like Round-up) and it will kill the weed.  However, you must be careful not to spray or drip the product on any thing except the weed.

Q: Even though it is winter I have two types of weeds in my lawn which seem to be thriving. One of the weeds has small white flowers on it and the other looks like clover with small yellow flowers. What kind of weeds are these?

A : It is difficult to determine the identity of plants over the phone, Yellow woodsorrelbut after seeing these weeds the mystery became easy. Both are very common broad-leafed weeds and as you noted grow very well in the winter. Common chickweed, Stellaria media, is the one that produces the white flower. It is a mat-forming winter annual that reproduces by seed and is found throughout North America except for the Rocky Mountains. The other weed is called Yellow Woodsorrel, Oxalis stricta, which is a perennial. It is found in most of the eastern and central United States and reproduces by seed. Yellow Woodsorrel or Oxalis comes in a creeping and upright form; it also has attractive heart-shaped leaves which look similar to clover.

Q: While applying a weed killer (herbicide) to my lawn, some of the weed killer got around the roots of my shrubs and now portions of the shrubs are damaged. What can I apply to correct the damage? Would it help to put out some fertilizer?

A: Once the shrub is damaged by an herbicide or weed killer, the damage is permanent. It doesn’t mean the shrub will completely die, only the portions damaged. Applying fertilizer now, I believe, would complicate the problem because fertilizing the shrub would encourage new sprout and stem growth which would be exceptionally tender should we experience a cold snap or drastic drops in temperatures. It is best to keep the plant watered properly then take a “wait and see” attitude. Hopefully by next spring any new growth will cover the branches and foliage lost this year to the herbicide. You can remove any of the dead branches now if you like, but other than that, let the plant do its best to recover on its own. If you were using a broadcast spreader to apply your herbicide, consider purchasing a shield to limit the broadcast area. In the future you may want to avoid applying herbicides near the flower, tree and shrub areas.

Yellow Nut Sedge

Q: I have a weed in my yard that looks like fine grass, but I when I dig it up the root it has a small, round ball attached to it. It is so aggressive that it even pops up through the weed cloth I have put down in my flower beds. What is this weed?

A: Probably what you have is a yellow nut sedge and you are correct in Yellow nutsedgestating it is aggressive. It is a rapidly spreading perennial that puts out a long stem and a yellow-brown seed head. Stems of sedges are triangular (“sedges have edges”) whereas grass stems are hollow and round. It reproduces mainly by tubers and is found throughout the United States. Several herbicides can temporarily suppress yellow nutsedge populations; however, eradication of established nutsedge in lawn grass is extremely difficult. Some herbicides kill the yellow nutsedge plant tissue, however new plants can emerge from the tubers in the soil. Although it looks similar to grass the leaves of sedges are thicker and stiffer than most grasses. In addition, yellow nutsedge is a lighter yellow green color than St. Augustine grass. Sedges in general prefer moist soils so their presence may be an indication of too much water or the area is lower than the rest of your landscape. If over watering is contributing to the problem, reducing the amount of water may be beneficial.