Common Name: Chamal

General Information

Dioon edule is a slow-growing, evergreen, palm-like plant with an erect or decumbent, unbranched main stem that can eventually be up to 3 metres tall and 20 - 40cm in diameter; this is topped by a crown of numerous large leaves each around 90 - 150cm long[].
The edible seed is gathered from the wild and used locally. There is a long history of the use of this plant as a food in Mexico - in the past it was often used as a staple food, though now it is more likely to be used only in times of food shortage.
This species has been affected by habitat destruction and over-collecting for ornamental purposes. Some populations have declined substantially, but overall decline is relatively low. The plant is classified as 'Near Threatened' in the IUCN Red List of Threatened Species(2010)[].

Known Hazards

We have no specific information for this species, but most if not all members of this genus are believed to contain toxins. The two main toxic compounds that have been identified are cycasin and macrozamin. When ingested in sufficient quantities, these compounds are extremely poisonous to humans and many other animals, and have been shown to cause liver damage and cancer. Cycasin and macrozamin have a cumulative effect upon the body and are suspected of causing neurological disorders when ingested in small amounts over long periods of time.
There is a long history of human use of this genus as a starch-rich food, but it should be noted that the plants needed to be treated in various ways in order to remove any toxic principles. Caution should be exercised even with properly prepared foods, since even then regular consumption may lead to severe health problems and death. Since many of these species are becoming increasingly rare in the wild, this is probably a food best left to times of food shortage when other, better foods, are not available[, ].

Botanical References

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Range

C. America - eastern Mexico

Habitat

Deciduous and oak forests at elevations from sea level to 1,500 metres[]. Found in areas transitional between tropical deciduous forest and oak woodland, in rocky areas and on steep cliffs[].

Properties

Conservation Status	Near Threatened
Edibility Rating
Medicinal Rating
Habit	Evergreen Tree
Height	1.50 m
Growth Rate	Slow
Pollinators	Weevils
Self-fertile	No
Cultivation Status	Ornamental, Wild

Cultivation Details

Dioon edule is a plant of mainly subtropical areas, it can also be grown in the warm temperate zone. Plants can tolerate occasional frosts with temperatures down to -5°c[, ]. Dioon species are often frost tolerant to several degrees below freezing, but lower temperatures will cause foliar damage or complete defoliation. High temperatures and full sun do not usually cause damage, even to forest-dwelling species[].
Most species of Dioon are easily cultivated and grow with minimal care[]. This species prefers a position in full sun, but is tolerant of some shade[]. Requires a well-drained soil[]. Plants are able to grow in low light intensities and on poor soils[].
The stems of Dioon species are clothed in a thick armour of old leaf bases that protect them from the frequent fires that pass through their habitat. Their trunks are also clothed in a thick layer of dense, wooly hairs which persist and give protection until burned off[].
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[].
Female plants only produce one seed cone at each reproductive cycle, which generally occurs once every three to four years. This cone take around 8 - 9 months to mature[]. The ovoid cones of this species are 25 - 29cm long and 19 - 24cm in diameter, covered with a dense layer of short woolly hairs[].

Edible Uses

The starch-rich seed can be eaten boiled or roasted[, , ]. A starch can be extracted from the seed - called Mexican arrowroot, it is used in making tortillas[].

Medicinal

A decoction of the seeds is used to treat neuralgia[, ].

Other Uses

A gum can be obtained from the petiole[]. No more details.

Propagation

Seed - surface sow on damp sand at a temperature of 24 - 32°c[]. On emergence of the radicle, pot the seedling into its own pot of a sandy compost and grow on in shaded warm conditions[]. Avoid any damage to the taproot and coralloid roots when repotting. Repot and feed frequently to encourage development and plant out when whorls of leaves are being produced, which can be 4 - 8 years[].

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