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Cycas revoluta

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Japanese sago palm
Cycas revoluta male reproductive cone
CITES Appendix II (CITES)[2]
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Gymnospermae
Division: Cycadophyta
Class: Cycadopsida
Order: Cycadales
Family: Cycadaceae
Genus: Cycas
C. revoluta
Binomial name
Cycas revoluta
  • Cycas aurea J.Verschaff.
  • Cycas inermis Oudem.
  • Cycas miquelii Warb.
  • Cycas taitungensis
    C.F. Shen, K.D. Hill, C.H. Tsou & C.J. Chen
  • Epicycas miquelii (Warb.) de Laub.

Cycas revoluta (Sotetsu [Japanese ソテツ], sago palm, king sago, sago cycad, Japanese sago palm) is a species of gymnosperm in the family Cycadaceae, native to southern Japan including the Ryukyu Islands. It is one of several species used for the production of sago, as well as an ornamental plant. The sago cycad can be distinguished by a thick coat of fibers on its trunk. The sago cycad is sometimes mistakenly thought to be a palm, although the only similarity between the two is that they look similar and both produce seeds.


Cycads' only relations to the true palms (Arecaceae) is that both are vascular plants and seed plants. The Latin specific epithet revoluta means "curled back",[5] in reference to the leaves. This is also called kungi (comb) palm in Urdu speaking areas.[6]


This very symmetrical plant supports a crown of shiny, dark green leaves on a thick shaggy trunk that is typically about 20 cm (7.9 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 several times, thus producing multiple heads of leaves.[7]

King sago palm in Humble, Texas.

The leaves are a deep semiglossy green and about 50–150 cm (20–59 in) long when the plants are of a reproductive age. They grow out into a feather-like rosette to 1 m (3.3 ft) in diameter. The crowded, stiff, narrow leaflets are 8–18 cm (3.1–7.1 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 (2.4–3.9 in) long and have small protective barbs.[citation needed]

Roots are called coralloid with an Anabaena symbiosis allowing nitrogen fixation.[8] Tannins-rich cells are found on either side of the algal layer to resist the algal invasion.[citation needed]

As with other cycads, it is dioecious, with the males bearing pollen cones (strobilus) and the females bearing groups of megasporophylls. Pollination can be done naturally by insects or artificially.

Cultivation and uses[edit]

Propagation of Cycas revoluta is either by seed or clonally by removal of basal offsets. 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, 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.[citation needed]

Plant covered with snow.

Of all the cycads, C. revoluta is the most popular in cultivation. 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 18th century, it is tolerant of mild to somewhat cold temperatures, provided the ground is dry. Frost damage can occur at temperatures below −10 °C (14 °F). C. revoluta usually defoliates in winter in this temperate climate, but will usually flush (grow) several new leaves by spring.

This plant has gained the Royal Horticultural Society's Award of Garden Merit[9] (confirmed 2017).[10]


The pith contains edible starch, and is used for making sago. Before use, the starch must be carefully washed to leach out toxins contained in the pith. Extracting edible starch from the sago cycad requires special care due to the poisonous nature of cycads.[11] Cycad sago is used for many of the same purposes as palm sago. Sago is extracted from the sago cycad by cutting the pith from the stem, root and seeds of the cycads, grinding the pith to a coarse flour and then washing it carefully and repeatedly to leach out the natural toxins. The starchy residue is then dried and cooked, producing a starch similar to palm sago/sabudana. The cycad seed contains cycasin toxin and should not be eaten as it is possible for cycasin toxin to survive the most vigorous of repeated washings. Cycasin toxin can cause ALS, Parkinson's, prostate cancer and fibrolamellar hepatocellular carcinoma.[citation needed]

Aulacaspis yasumatsui is a scale insect feeding on C. revoluta, and unchecked is able to destroy the plant.[12]


Example of a full-grown tree

The hydro-alcoholic extract of leaves of C. revoluta shows the presence of alkaloids, steroids and tannins while the chloroform extract shows the presence of saponins, tannins and sugars.[13] Leaflets also contain biflavonoids.[14] Estragole is the primary volatile compound emitted from the male and female cones of C. revoluta.[15]


Cycad sago is extremely poisonous to animals (including humans) if ingested. Pets are at particular risk, since they seem to find the plant very palatable.[16] Clinical symptoms of ingestion 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 appear bruised, have nose bleeds (epistaxis), melena (blood in the stool), hematochezia (bloody straining), and hemarthrosis (blood in the joints).[17] The ASPCA Animal Poison Control Center estimates a fatality rate of 50 to 75% when ingestion of the sago palm is involved. 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.[18] 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.[19]


See also[edit]


  1. ^ Hill, K.D. (2010). "Cycas revoluta". IUCN Red List of Threatened Species. 2010: e.T42080A10622557. doi:10.2305/IUCN.UK.2010-3.RLTS.T42080A10622557.en. Retrieved 12 November 2021.
  2. ^ "Appendices | CITES". cites.org. Retrieved 2022-01-14.
  3. ^ Plants of the World Online. "Cycas revoluta Thunb". Royal Botanic Gardens. Retrieved 2022-05-22.
  4. ^ Chang, J.-T.; Chao, C.-T.; Nakamura, K.; Liu, H.-L.; Luo, M.-X.; Liao, P.-C. (2022). "Divergence With Gene Flow and Contrasting Population Size Blur the Species Boundary in Cycas Sect. Asiorientales, as Inferred From Morphology and RAD-Seq Data". Frontiers in Plant Science. 13: 824158. doi:10.3389/fpls.2022.824158. ISSN 1664-462X. PMC 9125193. PMID 35615129.
  5. ^ Gledhill, D. (2008). The Names of Plants. Cambridge University Press. p. 329. ISBN 9780521866453.
  6. ^ Harrison, Lorraine (2012). RHS Latin for gardeners. United Kingdom: Mitchell Beazley. p. 224. ISBN 9781845337315.
  7. ^ Thunberg, Carl Peter. 1782. Verhandelingen uitgegeeven door de hollandse maatschappy der weetenschappen, te Haarlem 20(2): 424, 426–427.
  8. ^ Ultrastructure and phenolic histochemistry of the Cycas revoluta-Anabaena symbiosis. M. Obukowicz, M. Schaller and G.S. Kennedy, New Phytologist, April 1981, Volume 87, Issue 4, pages 751–759, doi:10.1111/j.1469-8137.1981.tb01711.x
  9. ^ "Cycas revoluta". Royal Horticultural Society. Retrieved 14 April 2020.
  10. ^ "AGM Plants - Ornamental" (PDF). Royal Horticultural Society. July 2017. p. 22. Retrieved 24 January 2018.
  11. ^ Lafferty, Jamie (2020-01-07). "How a Plant Saved a Japanese Island". BBC.
  12. ^ Aulacaspis yasumatsui (Hemiptera: Sternorrhyncha: Diaspididae), a Scale Insect Pest of Cycads Recently Introduced into Florida. Forrest W. Howard, Avas Hamon, Michael Mclaughlin, Thomas Weissling and Si-lin Yang, The Florida Entomologist, March 1999, Vol. 82, No. 1, pages 14-27 (article)
  13. ^ Leaves Of Cycas revoluta: Potent Antimicrobial And Antioxidant Agent. Manoj K Mourya, Archana Prakash, Ajay Swami, Gautam K Singh and Abhishek Mathur, World Journal of Science and Technology, 2011, Vol 1, No 10, pages 11-20 (article)
  14. ^ Phytochemical Investigation of Cycas circinalis and Cycas revoluta Leaflets: Moderately Active Antibacterial Biflavonoids. Abeer Moawad, Mona Hetta, Jordan K. Zjawiony, Melissa R. Jacob, Mohamed Hifnawy, Jannie P. J. Marais and Daneel Ferreira, Planta Med., 2010, 76(8), pages 796-802, doi:10.1055/s-0029-1240743
  15. ^ Estragole (4-allylanisole) is the primary compound in volatiles emitted from the male and female cones of Cycas revoluta. Hiroshi Azuma and Masumi Kono, Journal of Plant Research, November 2006, Volume 119, Issue 6, pages 671-676, doi:10.1007/s10265-006-0019-2
  16. ^ Suspected cycad (Cycas revoluta) intoxication in dogs, Botha CJ, Naude TW, Swan GE, et al.| J S Afr Vet Assoc | 1991
  17. ^ Muller-Esneault, Susan (2009). "Cycas Revoluta: The Sago Palm, or Cycad Toxicity". Critterology.com. Archived from the original on 2012-06-05. Retrieved 2009-05-12.
  18. ^ Selected poisonous plant concerns small animals, Knight MW, Dorman DC | Vet Med | 1997 | 92(3):260-272
  19. ^ Toxicology Brief: Cycad toxicosis in dogs, Hany Youssef| Veterinary Medicine | May 1, 2008 | [1]

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