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Cycas revoluta
Thunb.
Sago-palm
Cycadaceae
Cycas revoluta is a species of tree-sized cycad in the family Cycadaceae. It is native to the Ryukyu Islands and Kyushu of Japan. It is by far the most commonly grown cycad. In the Ryukyu Islands, it was used as a food source despite its toxicity.
Description
Cycas revoluta is a tree, 3 (sometimes up to 8) m tall, and occasionally multi-trunked: it resembles a palm since it forms a rosette of large leaves at the top, and is known by some confusing names, such as "sago-palm", despite the fact that it is not closely related to palms. Leaves are huge, 0.7 to 1.4 m long and 20 to 25 cm wide, pinnate, on a 10 to 20 cm long, spiny leafstalk. Each leaf has 60 to 150 pairs of slightly curved, stiff leaflets that are 10 to 20 cm long, 4 to 7 mm wide, sharply pointed. Leaves are tightly curled up, hairy brown when young; leaflets are bent upwards. The bark is dark gray, scaly. Male (pollen) cones, are large, yellow, 30 to 60 cm tall and 8 to 15 cm wide, ovoid. Seeds are borne on separate trees. They are borne in clusters of 2 (or up to 5), orange-red, ellipsoidal, 4 to 5 cm long and about 3 cm wide, with a few hairs. They are surrounded by leaf-like structures called megasporophylls that are 6 to 11 cm long, 4 to 7 cm wide, straw-colored, hairy and deeply divided. Pollination occurs from May to July, and the seeds become mature in early fall (Wu et al. 1999).
All cycad species are highly toxic, and this species is no exception. The toxic compounds have not all been identified yet, but one important toxin is cycasin (Whitelock 2003). Symptoms of poisoning include excessive perspiration, vomiting, and eventually loss of consciousness. In the Ryukyu Islands where it is native, the presence cycad starch in the diet of native inhabitants is thought to cause neurological diseases such as amyotrophic lateral sclerosis or dementia. A process, although extremely arduous, exists to remove the toxins from the starch in seeds and stems (Whitelock 2003).
All cycad species are highly toxic, and this species is no exception. The toxic compounds have not all been identified yet, but one important toxin is cycasin (Whitelock 2003). Symptoms of poisoning include excessive perspiration, vomiting, and eventually loss of consciousness. In the Ryukyu Islands where it is native, the presence cycad starch in the diet of native inhabitants is thought to cause neurological diseases such as amyotrophic lateral sclerosis or dementia. A process, although extremely arduous, exists to remove the toxins from the starch in seeds and stems (Whitelock 2003).
Uses
Note: Please see the disclaimer regarding any information about medical or edible uses.
Cycas revoluta is very common as a houseplant or as an ornamental in warmer climates. It is hardy in USDA zones 9 to 10, and prefers sandy, well-drained soils in partial shade. While it grows slowly and may take time to grow a trunk (MBG), its growth rate is still much higher than other cycads. In China and Japan plants are grown as bonsai specimens (Whitelock 2003).
Leaves of Cycas revoluta are popular for floral arrangements or palm fronds for Palm Sunday, although it is not a palm. This is most common in the United States and Europe, since in Asia the leaves are used as funeral decorations, making them associated with death. In the Ryukyu Islands, the plant was used for food in various ways, despite its toxicity. For example, starch was extracted from stems and leaves, alcoholic drinks from fermented seeds, and its new leaves were used as a vegetable (Whitelock 2003).
Leaves of Cycas revoluta are popular for floral arrangements or palm fronds for Palm Sunday, although it is not a palm. This is most common in the United States and Europe, since in Asia the leaves are used as funeral decorations, making them associated with death. In the Ryukyu Islands, the plant was used for food in various ways, despite its toxicity. For example, starch was extracted from stems and leaves, alcoholic drinks from fermented seeds, and its new leaves were used as a vegetable (Whitelock 2003).
Distribution
Cycas revoluta grows on hillsides or scattered in forests, at an altitude of 100 to 500 m. It is mainly found in Kyushu and the Ryukyu Islands of Japan. It is unknown whether there are currently populations in Fujian, China (Wu et al. 1999; Hill 2016).
Status
Cycas revoluta is listed on the IUCN Red List as "Least Concern". The plant is fairly common in Japan where it is native, and although there is some habitat destruction and harvesting, it is currently not enough to threaten the population (Hill 2016).
References
Hill, K. D. 2016. Cycas revoluta. The IUCN Red List of Threatened Species. https://dx.doi.org/10.2305/IUCN.UK.2010-3.RLTS.T42080A10622557.en.
MBG (Missouri Botanical Garden), Cycas revoluta. Plant Finder. [accessed 2019 Jun 12]. http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=279640&isprofile=0&
Whitelock, L. M. 2003. The Cycads. Portland: Timber Press.
Wu, Z. Y., Raven, P. H., and Hong, D. Y., eds. 1999. Flora of China. Vol. 4 (Cycadaceae through Fagaceae). Beijing: Science Press, and St. Louis: Missouri Botanical Garden Press.
MBG (Missouri Botanical Garden), Cycas revoluta. Plant Finder. [accessed 2019 Jun 12]. http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=279640&isprofile=0&
Whitelock, L. M. 2003. The Cycads. Portland: Timber Press.
Wu, Z. Y., Raven, P. H., and Hong, D. Y., eds. 1999. Flora of China. Vol. 4 (Cycadaceae through Fagaceae). Beijing: Science Press, and St. Louis: Missouri Botanical Garden Press.
Description
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