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engraving

Illustration of Dioon edule from the Botanical Magazine 101, tab.6184, (1875) (Jones 1993).

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Distribution of Dioon species (redrawn from Jones 1993).

 

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Dioon edule

Lindley 1843

Common Names

Taxonomic notes

Type species of the genus. Closely related to D. merolae and D. holmgrenii, which all have leaves "rather stiff and erect or semi-erect, with stiff, sharp-pointed leaflets closely spaced and often overlapping (i.e., imbricated)" (Norstog and Nichols 1997). A diverse species; several varieties have been described. Jones (1993) recognizes one variety, Dioon edule var. angustifolium (Miquel) Miquel 1848 (syn: D. angustifolium Miquel).

Description

Medium-sized cycad with erect or reclining trunk 1-1.5(-3) m tall and 20-30 cm diameter. Young leaves pale green, shortly hairy. Mature leaves 15-20 in a stiff, obliquely erect crown, 0.7-1.6 m long, stiff, rigid, light green or glaucous, flat in cross-section, straight in profile, broadest near the middle and tapered to each end; petiole 10-15 cm long, swollen at the base, lacking prickles; leaflets 120-160 on each leaf, moderately spaced but those toward the apex often crowded and overlapping, inserted at 60-90° to the rachis, lacking marginal spines; median leaflets 6-12 cm by 6-10 mm, linear to linear-lanceolate, leathery, tapered and long-acuminate, gradually reduced in length toward the base of the leaf. Male cones 20-40 × 6-10 cm cylindical; sporophylls 2-3 cm long with upcurved pointed tips. Female cones 20-35 × 12-20 cm, ovoid, wooly; sporophylls 5-8.5 cm long; peduncle 8-12 cm long. Seeds 2.5-3.5 × 2-2.5 cm, ovoid (Jones 1993, Norstog and Nichols 1997).

Var. angustifolium differs from the type in having narrower leaflets (6-11 cm × 4-6 mm) that are generally glaucous when young and inserted to the rachis at an acute angle; and in having smaller seeds (about 2 × 2 cm) (Jones 1993).

Distribution and Ecology

Mexico: widely distributed in the Sierra Madre Oriental from sea level to 1500m. This variety is found in central Veracruz, Queretaro, northern Hidalgo, San Luis Potosi and southern Tamaulipas. Most commonly found in tropical deciduous and oak forests. Var. angustifolium is restricted to the northern Sierra Medre Oriental, in parts of Tamaulipas and Nuevo Leon at 200-1500m (Jones 1993).

Big tree

Ethnobotany

Young seeds are ground and cooked into tortillas. Fronds are used for decoration, especially in religious ceremonies. Western cultures have widely adopted this variety as an ornamental (Jones 1993).

Observations

A common species in collections. Have not seen in habitat.

Remarks

"The foliage is characteristically gray-green to glaucous, a feature of many cycad forms adapted to xeric conditions that is also to be noted in some macrozamias and encephalartoses, and the species in this complex are often found in harsh, dry habitats in eastern Mexico" (Norstog and Nichols 1997).

Citations

See also

Last Modified 2012-11-28