- Category: Plants
HabitatGenerally in areas transitional between tropical deciduus forest and oak woodland, in rocky habitats or on steep cliffs, at elevations of 500 - 1500 m (1600 - 4900 ft). Rainfall averages 1000 - 1500 mm (39 - 59 in) annually, falling mainly in summer.
DistributionMexico, in Hidalgo, Queretaro, San Louis Potosi, southern Tamaulipas, and Veracruz states, along the eastern slopes of the Sierra Madre Oriental.
The range of Dioon along the eastern coast of Mexico is broken into numerous populations, each showing variation in one respect or another. These populations should great variability in leaf length and width, angle of insertion of the leaflets, leaflet width, leaflet margins, elevational range, and so on.
Variations worth of mention include the following, arranged by state, north to south.
Valles formSan Luis Potosi, elevation about 150 m (500 ft). Stems seldom reaching 30 cm (12 in) tall, producing numerous offsets tightly crowded around the parent. Leaves 55 - 57.5 (22 - 23 in) long, 10 cm (4 in) wide. Female cones about 14 cm (5.5 in) long, 9 cm (3.6 in) in diameter, densely tomentose. Male cones 5.5 - 8 cm (2.2 - 3.2 in) long, 3 - 4 cm (1.2 - 1.6 in) in diameter, almost glabrous.
Rio Verde formSan Luis Potosi, elevations of 230 - 300 m (750 - 980 ft). Stems 1.5 - 1.8 m (4.9 - 5.9 ft) tall, 22.5 cm (8.9 in) in diameter. Leaves slightly arching, about 1.2 m (3.9 ft) long and 16.5 cm (6.5 in) wide, flat, leaves and leaflets intense blue-grey when new. Female cones small, sporophylls long, narrow. Seeds small. "Sarcotesta distinctively light yellow.
Queretaro formQueretaro, elevation about 1230 m (4000 ft). Stems to about 1.2 m (3.9 ft) tall. Leaves slightly twisted, slightly curved inward, about 84 cm (33 in) long and 21 cm (8.3 in) wide, flat, emergent leaves an intense blue-grey. Leaflets with strongly revolute margins. Female cones with short sporophylls, blunt apexes.
Jacala formHidalgo, elevation about 1400 m (4500 ft). Stems to 3 m (10 ft) long, often decumbent. Leaves stiff, glossy bright green, about 1.2 m (3.9 ft) long and 22.5 cm (8.9 in) wide, flat. Rachis distinctly yellowish. Leaflets with strongly revolute margins. Male cones somewhat glabrous, only the sporophyll apex with a patch of light brown tomentum.
Palma Sola formVeracruz, from sea level to about 200 m (650 ft). Stems medium sized. Leaves numerous, 0.9 - 1 m (2.9 - 3.3 ft) long, 16.5 cm (6.5 in) wide, unlike variety edule the leaves keeled, with crowded, overlapping leaflets in the apical third to half of the leaf. Sarcotesta uniquely orange-yellow.
All of these variations are easily grown and respond well to cultivation. Some, like Dioon edule var. angustifolium, are dwarfs and have a very slow growth rate. Most of the others have a relatively rapid growth rate if given good soil and sufficient water and fertilizer. The seeds need about 6 - 8 months to form the embryo after being shed from the cone. At that point germination is rapid, but the formation of the first leaf varies considerably, depending on the variety being grown. Seed of D. edule stores well and will keep two to three seasons without noticeable loss of viability.