Common Name: Japanese Sago Palm

General Information

Cycas revoluta is a slow-growing, evergreen palm-like plant with an erect main stem that is usually around 0.5 - 2 metres tall (though up to 8 metres in very old specimens) and around 20 - 90cm in diameter; this is topped by a crown of numerouslarge leaves each around 60 - 150cm long. Older specimens, especially if male, are likely to have one or more branches.[].
The plant is harvested from the wild for local use as a food and medicine. It is sometimes cultivated as a food plant in Japan, Taiwan and India[], and is also commonly grown as an ornamental in gardens and parks, and is a popular bonsai subject[, ]. The leaves are used as decorative material, and have been exported in quantity from Japan for this purpose[].
Plants occur primarily on steep to precipitous stony sites, but previously they occurred on flatter land which has since been cleared. There has been massive seed collecting from natural habitats and leaves are exported in large numbers for decorative purposes. Current populations are considered to be stable and so the plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2010)[].

Known Hazards

The plants contain alkaloids of carcinogens and also an amino-acid that causes chronic nervous disorders[]. Regular consumption of the plant leads to severe health problems and death. This toxic principle can be removed if the food is properly prepared but consumption of the plant still cannot be recommended because its use often means the death of the plant and it is becoming rare in the wild.

Botanical References

, ,

Range

E. Asia - southern China, southern Japan.

Habitat

Found mainly on the sea shore in S. Japan[]. Thickets on hillsides on islands, sparse forests on mainland at elevations of 100 - 500 metres in E. China[]. Primarily on steep to precipitous stony sites, but previously on flatter land now cleared[].

Properties

Conservation Status	Least Concern
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	3.50 m
Growth Rate	Slow
Pollinators	Insects, wind
Self-fertile	No
Cultivation Status	Cultivated, Ornamental, Wild

Cultivation Details

Cycas revoluta is probably the hardiest cycad, able to tolerate light frosts, with reports of plants withstanding temperatures as low as -6°c[, ]. It can be grown from the warm temperate zone through to the tropics[].
Requires a sunny position[]. Plants are sometimes found in dense shade in the wild[]. Requires a strong loam with sharp sand and good drainage[]. Succeeds in dry soils. Plants are tolerant of saline conditions[].
Plants are very slow growing[, ].
This plant is often used as a food source in its native range but recent research has shown that it can cause chronic nervous disorders if it is not treated properly[]. Overall its use is not to be recommended, especially since it is becoming rare in the wild.
Species in this genus can usually be transplanted easily even when quite large. The best time for moving them is just before the beginning of a new growing season, the roots being trimmed if they are damaged and perhaps some leaves being removed. New roots should develop quickly as the season progresses[].
Species in this genus form structures known as coralloid roots. These roots branch off from the taproot or secondary roots and are distinctive in that they grow laterally or upward, forming a nodular mass at the apex. These coralloid roots occur slightly below or slightly above the soil surface and generally contain cyanobacteria, also known as blue-green algae. These are able to fix atmospheric nitrogen and make it available as a nutrient to the plant. The ability to extract this important nutrient from the air explains how many cycad species are able to survive on almost sterile soils[].
A dioecious species, with individual plants producing either all male or all female cones. Therefore both male and female forms of the plant need to be grown if seed is required[]. On very rare occasions, usually when a plant has been under severe stress, it can change sex and produce either all female or all male cones[].

Edible Uses

Species in this genus are generally toxic unless the food is prepared correctly. See notes above on toxicity.

Seed - raw or cooked[, , ]. Both the fleshy testa, which is said to have a sweet mucilaginous taste, and the starchy kernel of the seed are edible[]. The ovoid seeds are around 30 - 40mm long and 25 - 30mm wide[]. A nourishing food when properly prepared, the seed kernels contain around 12 - 14% crude protein and 66 - 70% starch[]. It has been reported that 100 kilos of seed kernels will produce 27 kilos of pure starch[]
The seeds can be dried and ground into a powder then mixed with brown rice and fermented into 'date miso' or 'sotetsu miso'[]. Caution is advised, see the notes above on toxicity.

The seeds can contain up to 23% oil and this has been used as a food in times of emergency[].

The heart or pith of the trunk is sliced and eaten baked or powdered[]. It is often used in quantity during times of need, but is little used when other foods are available[]. A toxic principal must first be removed[]. A starch can be extracted from this pith and is used for making dumplings[]. It is very sustaining[, ]. The starch content of male plants is distinctly higher than that of female plants, varying from 27 - 61% and averaging around 50% throughout the year compared to an average of 26% in female plants[].
The starch obtained from the seed and stem pith has been used in the manufacture of a drink similar to sake. The resultant liquor is always slightly poisonous, and on rare occasions, a particularly toxic batch has been known to kill all who consumed it[].
To be suitable for the extraction of starch, the plant should not have fruited, as fruiting depletes the store of starch in the stem. Most Cycas plants are capable of yielding large amounts of starch at around 7 years of age. The best time for the extraction of starch is just before a flush of new leaves[].

Root notules[]. The white flesh is somewhat, potato-like, with a peculiar, sweetish, mild, not unpleasant flavour. When cooked, the nodules have an insipid, slightly sweet taste[]. The root nodules contain around 18% starch[]

The young leaves are said to be used for food[].

Medicinal

The leaves are used in the treatment of cancer and hepatoma[].

The terminal shoot is astringent and diuretic[].

The seed is emmenagogue, expectorant and tonic[]. It is used in the treatment of rheumatism[]. Substances extracted from the seeds are used to inhibit the growth of malignant tumours[].

A gum obtained from the plant has been used medicinally, particularly as an agent that is said to produce rapid suppuration when applied to malignant ulcers. The gum also has the repute of being a good antidote for snake and insect bites[].

Other Uses

The dried and powdered leaves are used as an ingredient in commercial cosmetic preparations as an abrasive and skin conditioner[].

A starch obtained from the stems and seeds has been used as a laundry starch[].

Surface fibres from the leaves have been made into cloth[].

A gum exudes through wounds in the plant, especially from the megasporophylls, stems and leaves[]. It is used medicinally and as an adhesive[].
When placed in water, Cycas gum begins to swell almost immediately. By the end of several days, it expands to many times its original size and becomes so colourless and transparent that it cannot be seen in water but must be felt for with a rod[]. Cycas gum has been likened in its properties to that of Sterculia setigera[]

The seeds can contain up to 23% oil[].

The wood is said to be beautifully spotted but very light and porous. It has been used to make small articles such as boxes, plates, and bottle stands[].

Propagation

Seed - best sown in a greenhouse as soon as it is ripe, 2cm deep in individual pots which are then sealed in plastic bags to keep them moist until germination takes place. Germinates in 1 - 3 months at 25°c[]. Pre-soak stored seed for 24 hours in warm water then treat as above.
Division of suckers in the spring.