Cycas revoluta

Cycas revoluta (Sotetsu [Japanese ソテツ], sago cycad, sago palm, king sago, Japanese sago palm) is a species of gymnosperm (a group of woody seed-producing plants) in the family Cycadaceae, native to southern Japan including the Ryukyu Islands. It is one of several species used for making sago, as well as a decorative plant. The sago cycad can be told apart by a thick coat of fibers on its trunk. The sago cycad is sometimes wrongly thought to be a palm, although the only similarity between the two is that they look similar and both make seeds.

Cycads are not related to palms (Arecaceae), apparently similar only in how the leaves are arranged and that both are vascular plants and seed plants. The Latin name revoluta means "curled back",^[5] due to the curled leaves. This is also called kungi (comb) palm in Urdu speaking areas.^[6]

This very evenly-shaped plant has a set of shiny, dark green leaves arranged in a circle. They come out of a thick hairy trunk that is normally about 20 cm (7.9 in) in diameter, sometimes wider. The trunk is very low or below the ground in young plants, but grows above ground with age. It can grow into very old sago palms with 6–7 m (20–23 ft) of trunk; however, the plant is very slow-growing and requires about 50–100 years to grow to this height. Trunks can branch several times, making multiple heads of leaves.^[7] The largest human-grown sago palm, at the Ryugeji Temple, in Shimizu, Japan (136 km (85 mi) west south-west of Tokyo), is 8 m (26 ft) in height and 1.6 m (5 ft 3 in) thick.^[8]

Spread of Cycas revoluta is either by seed or by clones by removing parts of the base. It 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, ideally with some organic matter. It needs good drainage or it will rot. It is somewhat drought-tolerant and grows well in full sun or outdoor shade, but needs bright light when grown inside buildings. The leaves can whiten somewhat if moved from inside a building to full sun outdoors.

The pith (a material inside the plant) contains eatable starch, and is used for making sago. Before use, the starch must be carefully washed to clean out toxins inside the pith. Getting eatable starch from the sago cycad needs special care due to the toxic nature of cycads.^[9]

Cycad sago is extremely poisonous to animals (including humans) if eaten. Pets are a especially at risk, since they apparently find the plant very pleasant to eat.^[10] Clinical symptoms of eating the plant will develop within 12 hours, and may include vomiting, diarrhea, weakness, seizures, and liver failure or hepatotoxicity characterized by icterus, cirrhosis, and ascites. The pet may seem bruised, have nose bleeds (epistaxis), melena (blood in the stool), hematochezia (bloody straining), and hemarthrosis (blood in the joints).^[11] The ASPCA Animal Poison Control Center estimates a death rate of 50 to 75% when parts of a sago palm are eaten. If any quantity of the plant is eaten, a poison control center or doctor should be contacted immediately. Effects of eating the plant 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 quantities, leads the liver to stop working.^[12] Other toxins include Beta-methylamino L-alanine, a neurotoxic (toxic to the brain) amino acid, and an unidentified toxin which has been seen to cause paralysis in the hind limbs of cattle.^[13]

• Female flower
• Young leaves
• Young leaflets curled back, "revoluta"
• Seeds
• A 16-year-old two-branched sago palm
• Seeds and seed leaves
• Cycas revoluta at Azores

• The Cycad Pages: Cycas revoluta Archived 2020-09-03 at the Wayback Machine
• Sago Palm: University of Arizona Pima County Cooperative Extension
• The Sago Palm, Cycas revoluta by Phil Bergman
• Cycads: their evolution, toxins, herbivores and insect pollinators. Schneider D, Wink M, Sporer F, Lounibos P. Naturwissenschaften. 2002 Jul;89(7):281-94. Review.PubMed
• Microsporophyll
• Macrosporophyll
• Seeds
• Videos - Flavon's Wild herb and Alpine plants
• line drawing of Cycas revoluta, Manual of Vascular Plants of the Lower Yangtze Valley China Illustration fig. 31
• line drawing of Cycas revoluta, Flora of China Illustrations vol. 4, fig. 2, 1-6