Cycas revoluta

Cycas revoluta

Cycas revoluta (sago cycad), is an attractive plant 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 cycad.

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.

Cultivation and uses

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.

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 described 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 (86 to 95 F) for successful growth, making outdoor growing impossible in colder places such as northern Europe, even where winter temperatures are not too cold. One disadvantage of its domestic use is that it is poisonous to animals and humans.

Toxicity

Cycad Sago Palm is extremely poisonous to both humans and animals if ingested. Pets are at particular risk since they seem to find the plant very palatable. The ASPCA Animal Poison Control Center estimates a fatality rate of 50 to 75 percent when ingestion of the Sago Palm is involved. The incidence of Sago Palm ingestion by pets has risen by over 200% in the last five years. If any quantity of the plant is ingested, a poison control center or doctor should be contacted immediately. Effects of ingestion can include permanent internal damage and death.

All parts of the plant are toxic, however, the seeds contain the highest level of the toxin cycasin. Cycasin causes gastrointestinal irritation, and in high enough doses, leads to liver failure. Other toxins include Beta-methylamino L-alanine, a neurotoxic amino acid; and an unidentified toxin which has been observed to cause hindlimb paralysis in cattle.

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