Common Name: Coyolito de cerro

General Information

Dioon spinulosum is a slow-growing, evergreen palm-like plant producing an upright, unbranched stem up to 10 metres tall and 40cm in diameter, topped by a crown of numerous, large,arching leaves that can each be 150 - 200cm long on mature plants[, ].
The plant is harvested from the wild for local use as a food. The leaves are harvested for use as decorations and the plants are often grown as ornamentals[].
Dioon spinulosum is affected by severe habitat destruction as a result of farming, ranching and the creation of reservoirs. There has also been severe over-collection of the plant from the wild in the past. Data from known populations of Dioon spinulosum indicates a decline of between 50 - 90% in different subpopulations, with an estimated overall decline of 70% over the past 2 generations. The plant is classified as 'Endangered' 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

Range

Southern N. America - southern Mexico (Oaxaca, Veracruz)

Habitat

Lowland tropical evergreen rainforest on limestone hills and cliffs; at elevations up to 300 metres[, ]

Properties

Conservation Status	Endangered
Habit	Evergreen Tree
Height	8.00 m
Growth Rate	Slow
Pollinators	Weevils
Self-fertile	No
Cultivation Status	Ornamental, Wild

Cultivation Details

Dioon spinulosum is native to the tropical climate of southern Mexico. Annual rainfall averages more than 2,000 mm, falling mainly in the summer. Summers are hot and humid with frequent rains, whilst winters are warm and generally dry[]. The plant is somewhat frost tolerant, surviving occasional periods of 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[]. Plants are able to grow in low light intensities and on poor soils[].
Plants in the wild commonly grow out of cracks and pockets in solid rock. Seeds can germinate in small fissures in the cliffs, and growth can be painfully slow until the roots find their way to a pocket of soil. Large plants have been observed growing out of a small hole or fissure in a limestone cliff with one large root connecting them to a patch of soil some 10 metres distant[]
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[].
The tops of plants are often cut down in order to obtain the seeds or sell the tops for decorations. Unlike many other cycads, this species does not often sucker from the remaining rootstock after the upper portion of the plant has been removed. The portion of the trunk that is left slowly rots away, and a cycad that has taken hundreds of years to develop is just a memory[].
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 35 - 50cm long and 20 - 27cm in diameter, covered with a dense layer of short woolly hairs. They can weigh up to 18 kilos[].

Edible Uses

The kernels of the large seeds contain much starch and are said to be roasted or boiled and then eaten[]. The kernels are also used as a source of meal or starch[]. The ovoid seeds are 40 - 50mm long, 30 - 35mm wide[].
In order to remove any toxins, the seeds are shelled, ground to a powder, then washed several times in running water. The end product is a flour-like substance that is almost pure starch, it used to make tortillas[].

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

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

The pitch-like sap is chewed as a gum[].

Medicinal

None known

Other Uses

The dry, stony seedcoats are sometimes used as playthings or whistles[].

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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