Cycas revoluta (Sago Cycad), is a cycad native to southern Japan. Though often known by the common name of King Sago Palm, or just Sago Palm, it is not a palm at all, but a type of gymnosperm.
This very symmetrical plant supports a crown of shiny, dark green leaves on a thick shaggy trunk that is typically about 20 cm (8 in.) in diameter, sometimes wider. The trunk is very low to subterranean in young plants, but lengthens above ground with age. It can grow into very old specimens with 6–7 m (over 20 feet) of trunk; however, the plant is very slow-growing and requires about 50–100 years to achieve this height. Trunks can branch multiple times, thus producing multiple heads of leaves.
The leaves are a deep semiglossy green and about 50–150 cm (18-45 in.) long when the plants are of a reproductive age. They grow out into a feather-like rosette to 1 m (3 feet) in diameter. The crowded, stiff, narrow leaflets are 8–18 cm (~7 in.) long and have strongly recurved or revolute edges. The basal leaflets become more like spines. The petiole or stems of the Sago Cycad are 6–10 cm (2.5-4 in.) long and have small protective barbs that must be avoided.
Propagation of Cycas revoluta is either by seed or by removal of basal offsets. As with other cycads, it is dioecious, with the males bearing cones and the females bearing groups of megasporophylls . Pollination can be done naturally by insects or artificially.
Cycas revoluta is one of the most widely cultivated cycads, grown outdoors in warm temperate and subtropical regions, or under glass in colder areas. It grows best in sandy, well-drained soil, preferably with some organic matter. It needs good drainage or it will rot. It is fairly drought-tolerant and grows well in full sun or outdoor shade, but needs bright light when grown indoors. The leaves can bleach somewhat if moved from indoors to full sun outdoors.
The pith is very rich in edible starch, and is used for making sago. Before use, the starch must be carefully washed to leach out toxins contained in the pith.
Of all the cycads, the Sago Palm is the most popular in horticulture. It is seen in almost all botanical gardens, in both temperate and tropical locations. In many areas of the world, it is heavily promoted commercially as a landscape plant. It is also quite popular as a bonsai plant. First discovered in the late 1700s, it is native to various areas of southern Japan and is thus tolerant of mild to somewhat cold temperatures, provided the ground is dry. Frond damage can occur at temperatures below −5 °C. It does however require hot summers with mean temperatures of 30 to 35 °C for successful growth, making outdoor growing impossible in colder places such as northern Europe, even where winter temperatures are not too cold.
Photo by Libby Wilkes
Horticulture Agent IV
County Extension Director