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Dioon edule
Lindl.
Chestnut Dioon
Zamiaceae
Dioon edule is a large species of cycad in the family Zamiaceae. It is native to the eastern slopes of the Sierra Madre Oriental in Mexico, and is quite variable. It is common in cultivation, and its seeds have been used as food.
Description
Dioon edule is a tree-sized cycad, growing to about 3 m tall or more. Leaves are huge, 0.9 to 1.4 m long and 17.5 to 20 cm wide, pinnate, on a 3 to 13 cm long leafstalk lacking spines. Each leaf has 80 to 130 pairs of linear to lanceolate, stiff leaflets that are about 6 to 12 cm long and 5 to 9 mm wide. Leaves are green or yellow-brown when young, and lose their hair. The leaflets are attached at right angles to the main leafstalk, and with smooth margins rolled slightly downwards, i.e. revolute. Male (pollen) cones are large, hairy and yellowish orange, 17.5 to 20 cm tall and 6 to 7.5 cm wide, cylindrical, and covered with pale grayish hairs. The stalk is 3 to 3.5 cm long, but often too short to be noticed. Sporophylls (cone “scales”) are triangular, 12 to 15 mm wide, 10 mm high. Seeds are borne on separate trees. Female cones hold seeds, and are more round, ovoid, about 25 to 29 cm long, 19 to 24 cm wide, erect at first and then becoming drooping. Sporophylls are 6.5 to 7.2 mm long, with a triangular face. Seeds are about 2.4 to 3.0 cm long, 1.9 to 2.2 cm wide, smooth but with some longitudinal grooves, and yellow when ripe (Whitelock 2003).
Dioon edule has many local varieties, many of which have diverged far enough that they can be easily told apart even when young (Whitelock 2003). The Valles form has short stems only to 30 cm tall, with shorter leaves about 55 to 57.5 cm and smaller female and (especially) male cones; it is native to lower elevations of San Luis Potosí (about 150 m). The Río Verde form has distinctive light yellow seedcoats and its young leaves are blue-gray when young; it is found in San Luis Potosí at elevations of 230 to 300 m. The Querétaro form in higher elevations of Querétaro (1230 m) has blue-gray emergent leaves and leaflets with margins that more revolute. The Jacala form is a large cycad with stems up to 3 m long. It is found in Hidalgo at elevations of about 1400 m, and has bright glossy green leaves with yellowish stalks and revolute leaflet margins. The Palma Sola form, found in Veracruz at elevations below 200 m, has keeled, overlapping leaflets and orange-yellow seedcoats (Whitelock 2003).
A prominent variety angustifolium is native to the Mexican states of Nuevo León and Tamaulipas. It is similar to the main variety, but has narrower leaflets that are 6 to 11 cm long, 4 to 6 mm wide, and pointed forward. Female cones are smaller, 1.9 to 2.5 cm long and approximately as wide, irregularly roundish. Male cones are 20 cm tall and 7.5 cm wide, erect until the pollen is shed (Whitelock 2003).
Dioon edule has many local varieties, many of which have diverged far enough that they can be easily told apart even when young (Whitelock 2003). The Valles form has short stems only to 30 cm tall, with shorter leaves about 55 to 57.5 cm and smaller female and (especially) male cones; it is native to lower elevations of San Luis Potosí (about 150 m). The Río Verde form has distinctive light yellow seedcoats and its young leaves are blue-gray when young; it is found in San Luis Potosí at elevations of 230 to 300 m. The Querétaro form in higher elevations of Querétaro (1230 m) has blue-gray emergent leaves and leaflets with margins that more revolute. The Jacala form is a large cycad with stems up to 3 m long. It is found in Hidalgo at elevations of about 1400 m, and has bright glossy green leaves with yellowish stalks and revolute leaflet margins. The Palma Sola form, found in Veracruz at elevations below 200 m, has keeled, overlapping leaflets and orange-yellow seedcoats (Whitelock 2003).
A prominent variety angustifolium is native to the Mexican states of Nuevo León and Tamaulipas. It is similar to the main variety, but has narrower leaflets that are 6 to 11 cm long, 4 to 6 mm wide, and pointed forward. Female cones are smaller, 1.9 to 2.5 cm long and approximately as wide, irregularly roundish. Male cones are 20 cm tall and 7.5 cm wide, erect until the pollen is shed (Whitelock 2003).
Uses
Note: Please see the disclaimer regarding any information about medical or edible uses.
Dioon edule has long been used as a food item, as implied by its specific epithet “edule”, but this is now rare (Whitelock 2003). It is often grown as an ornamental. It is hardy to USDA zones 9 to 11, and prefers moist, well-drained soils in sun to part shade (MBG).
Distribution
Dioon edule is found in rocky areas or cliffs, between tropical deciduous forests and oak woodland, at an elevation of 500 to 1500 m. It is native to the eastern slopes of the Sierra Madre Oriental in the Mexican states of Veracruz, Hidalgo, Querétaro, San Luis Potosí, as well as southern Tamaulipas (Whitelock 2003).
Status
Dioon edule is listed on the IUCN Red List as "Near Threatened". It suffers from habitat destruction from agriculture, as well as over-collecting. It is listed in Appendix II of CITES, an international treaty regulating the trade of endangered species (Chemnick & Gregory 2010).
References
Chemnick, J., and Gregory, T. 2010. Dioon edule. The IUCN Red List of Threatened Species. https://dx.doi.org/10.2305/IUCN.UK.2010-3.RLTS.T42158A10643785.en.
MBG (Missouri Botanical Garden), Dioon edule. Plant Finder. [accessed 2018 Dec 08]. http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=e504
Whitelock, L. M. 2003. The Cycads. Portland: Timber Press.
MBG (Missouri Botanical Garden), Dioon edule. Plant Finder. [accessed 2018 Dec 08]. http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=e504
Whitelock, L. M. 2003. The Cycads. Portland: Timber Press.
Description
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