Common Name: Teosinte

General Information

Dioon mejiae is a slow-growing, evergreen, palm-like plant with an erect main stem that can eventually be up to 7.3 metres tall and 17 - 36cm in diameter; this is topped by a crown of numerous large leaves each around 1 - 2 metres long[].
The plant is a staple food for indigenous people in Honduras, where the plant is gathered in quantity from the wild[]. The leaves are often gathered from the wild for use as decorations and the plant is sometimes grown as an ornamental[].
The biggest threat to Dioon mejiae comes from habitat destruction as a result of the conversion of habitat to farmland and to a lesser extent the effects of logging and road-building on the habitat. Recent surveys in Honduras, however, indicate that there are many large and healthy subpopulations with little evidence of decline despite use by local people. The plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2013)[].

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

Range

C. America - Honduras

Habitat

An understorey component of semi-deciduous tropical rain forest, often found on steep slopes and in canyons, but also growing on flat terrain; at elevations from 265 - 500 metres[].

Properties

Conservation Status	Least Concern
Edibility Rating
Habit	Evergreen Tree
Height	6.00 m
Growth Rate	Slow
Pollinators	Weevils
Self-fertile	No
Cultivation Status	Ornamental, Wild

Cultivation Details

Dioon mejiae grows in a subtropical climate in Honduras in an area where the rain falls mainly in the summer[]. In cultivation it can also succeed in the tropics and in warm temperate areas with almost frost-free winters 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[]. Some populations of this species thrive in sandy soil or sandy to clayey alluvial deposits, while others grow in loamy, limestone-derived soils; in soils weathered from metamorphics (schists, gneisses); etc[]. 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 can take more than one year to mature[]. The ovoid cones of this species are 30 - 46cm long and 25 - 35cm in diameter, covered with a dense layer of short woolly hairs[].

Edible Uses

Seeds - ground into a powder[]. The seeds are boiled, ground into a powder and used to make a sort of tortilla[]. Said to have a fine flavour[]. The irregularly ovoid to subglobose seed is around 45 - 55mm long and 30 - 35mm in diameter[].

The fleshy testa of the seed can be used as a food[].

The stems are rich in starch and can be used to make a sago[].

Medicinal

None known

Other Uses

None known

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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