Dioon edule (a 10 years old seedling!)
They are extremely slow growing to our eyes but we must understand that they have been around for over 200 million years (remember these plants were around during the time of dinosaurs). Notice their distinctive character which reflects their antiquity and some very large specimens could possibly be several hundred years old. They truly are unequalled and intriguing living organisms that count the eons of time while we count the seconds. They are beauties.
 

Description: It is a woody dioecious, plant that superficially resemble a palm or a tree fern.
Stem: The trunk is usually unbranched or sparsely branched, palm-like and may reach 4 m of height under optimal conditions (Usually less), 20-50 cm diameter.
Leaves: Produces 15 to 150 leathery, featherlike (pinnate) leaves. They are spirally arranged in a cluster that extend radially at the summit of the stem, they are stiff, upright, light or bright green or blue or blue-green, semi-glossy to dull, 100-200 cm long, flat (not keeled) in section (opposing leaflets inserted at 180° on rachis), with 70-150 leaflets tappering to a sharp point; basal leaflets reducing to spines, petiole spine-free for 5 cm. They resemble futuristic radio antennae and are retained for some number of years.
Leaflets narrowly lanceolate, concolorous, not falcate, inserted at 90° to rachis, not overlapping; margins flat, entire; median leaflets 6-12 cm long, 5-10 mm wide.
Male Flowers: Pollen cones ovoid to fusiform, pale brown, 15-40 cm long, 6-10 cm diam. Microsporophyll apex 30 mm long, 20 mm wide.
Female cones: Seed cones ovoid, pale grey, 20-35 cm long, 12-20 cm diam. Megasporophyll apex 35 mm long, 25 mm wide.
Fruit: The seed cones entirely resemble those of truly coniferous genus Araucaria or a pineapple in form but the scales are feather-like and soft to the touch. A mature female cone may weigh 1-2 kg and contain up to 200 or more seeds. Eventually the cone unravels to reveal nut sized seeds with a thin leathery skin.
Seeds: Ovoid, cream or white, 25-45 mm long, 20-30 mm wide, they take more than a year to mature.


 

Two years old seedling.
 

Dioon edule (Santa Rita, Mexico)
 

WARNING: The leaflets of dioon taper to a sharp point. It is well advised to plant virgin's palm away from footpaths and walkways. Wear heavy gloves when handling or working close to the virgin's palm to avoid getting jabbed by the sharp points of the leaflets.

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Scientific name:  Dion edule J. Lindley
In: Edward's Bot. Reg. 29: misc. 59-60 (1843).

Type Specimen: cult., from Mexico, Lindley s.n. (holo CGE).

Origin:   Eastern coast of Mexico (Nuevo Leon, San Luis, Tamaulipas (var. angustifolium)

Habitat and ecology: They grows in tropical deciduous oak forests, and in harsh, dry conditions in steep hillsides on extremely steep slopes where the soils are skeletal and poor with few nutrients, in limestone, serpentine or in sandy soil, but they can also be found in more hospitable soils and shelter. Interestingly, Dioon edule specifically has the ability to contract its stem underground as it grows — thus maintaining relativity in the amount of trunk exposed. One suggested explanation for this strange (unplant-like) activity is to reduce its exposure to environmental stress and predation —. Also, they may go through prolonged periods of rest, revealed as narrowing in the diameter of the trunk.

Conservation status: Listed in CITES appendix 2.

Common Names include: Virgin's palm, Chestnut Dioon

Etymology: The genus name Dioon comes from the Greek, meaning "two egg", because the seeds are produced in pairs. The species name edule is derived from the Latin, meaning "edible".

Synonyms:  

• Dioon aculeatum Lem.
  Ill. Hort. 2. Misc. 92 (1855).
• Dioon imbricatum Miq.,
  Tijdschr. Wis-Natuurk. Wetensch. Eerste Kl. Kon. Ned. Inst. Wetensch. 1: 36 (1848).
• Dioon edule f. imbricatum (Miq.) Miq.,
  Arch. Néerl. Sci. Exact. Nat. 3: 427 (1868).
• Dioon strobilosum Lem.
  Ill. Hort. 10: Misc. 4. (1863).
• Dioon strobilaceum Lem. ex DC.
  Ill. Hort. 10: Misc. 4. (1863).
• Macrozamia littoralis Liebm. ex Dyer
  in Hemsl., Biol. Cent.-Amer., Bot. 3: ? (1884).
• Macrozamia pectinata Liebm. ex Dyer
  in Hemsl., Biol. Cent.-Amer., Bot. 3: ? (1884).
• Zamia maeleni Miq.
  Linnaea 18: 97 (1844).
• Zamia friderici-guilielmi hort. Parment. ex Miq.
  Prodr. Syst. Cycad.: 22 (1861), nom. nud.
• Zamia macleani Regel
  Gartenflora 25: 371 (1876), nom. nud.
• Zamia rigida Karw. ex J. Schust.
  in Engl., Pflanzenr. 4(1): 125 (1932), nom. nud.

There are several varieties of Dioon edule, and some put these varieties in different species categories. Most all look about the same except for minor variations in the leaf pattern of which two subspecies are currently accepted
• Dioon edule subsp. angustifolium
• Dioon edule subsp. edule

The giant dioon (Dioon spinulosum) is similar but larger in stature and less cold hardy.

Cultivation: They are very adaptable plants to just about any soil except muddy, non-draining clay. They are long lived and slow growing and a plant with 30cm of stem can be quite old (20-40 or more years). They prefer well drained, gritty soil with plenty of water, especially in dry weather. Naturally undemanding for nutrients, they responds very well to regular applications of fertilizer. Growth can be greatly improved through the application of fertilizers. Most growers find that a fertilizer having an even NPK (Nitrogen, Phosphorus, Potassium) balance, and supplemental trace elements, provides a good start for cycads. They thrives and grows best in partial shade. In cultivation prefers moist soil with good drainage for optimal growth. But they are eventually very drought resistant. Mature and established plants have been reported to tolerate temperatures down to -12ºC for some days.
Dioon edule is one of the most cold hardy cycads.
Propagation: Virgin's palm may be propagated by seeds or by division and replanting of the attractive offsets or "pups" formed at the base of the oldest plant. They are among the easiest plants to germinate. The seeds are about a large grape size and hard as a rock.
USES: The Indians of the region of origin have used the pulp of the seed as a source of flour (The young seeds are ground and cooked into tortillas) and also the stem of this plant contains abundance of starch, which may be extracted and used as arrow-root. We know little of the precautions used to prepare them for consumption, but since the skin of the seeds is reportedly carcinogenic we strongly advise the use of gloves when handling the seeds and caution against eating any parts of any cycad!
The leaves (fronds) of virgin's palm are used for decoration, especially in religious ceremonies.