Dioon edule (Cycad, Chestnut Dioon, Virgin Palm)

Native to tropical oak forests and dry regions, cycads have been around since the age of the dinosaurs. Being one of the cold-hardiest cycads with drought and salt tolerance, Dioon edule is frequently planted in Florida. However, cycads are still grown through out North America in tropical greenhouses. I had the pleasure of coming across several cycads while visiting SIU Carbondale in early February, with Doctor Stephen Ebbs and Vinny Colantonio, an undergraduate plant biology student, as my guides.

Dioon edule (Cycad, Chestnut Dioon, Virgin’s Palm) [sometimes called ‘Dioon imbricatum’ or ‘Dioon strobilaceum’]
Deciduous: no
Hardiness Zones: 9-11 (hardy to zone 8 if given proper protection)
Height: 2-2.5 meters (6-8 feet) tall, trunk short and thick (up to 130 centimeters (2 inches) in diameter)
Diameter: 1.3-1.8 meters (4-6 feet) wide at matuirty
Growth Rate: slow
Age: Cycads typically live for hundreds of years (D. edule’s close relative D. spinulosum, a larger and less cold hardy variety), supposedly to 1,000 years at absolute maximum
Root System: Some underground roots can be retracted to reduce damage caused by fire. Some roots contain cyanobacteria, which aid the plant by having the bacteria fix Nitrogen for the plant’s use.
Family: Zamiaceae
Subspecies: ‘angustifolium’ (northern variety of Central America), ‘edule’ (more widespread through Central America)

Tolerates: Nutrient poor soils, fire, deer, can grow in sandy or sloped soils
Problems (major): Cycad aulacaspis scale
Problems (minor): Caterpillars and other pests may eat some foliage.
Poisonous: yes (the entire plant contains poisonous properties)

Soil requirements: moist, humusy, well-drained soils are essential; fertilizer (balanced (even”Nitrogen-Phosphorus-Potassium” values) and contains trace elements) helps with growth. Natively found in clay soils with neutral of slightly alkaline pH.
Air Requirements: warm, dry air is typical of this cycad’s native habitat
Watering requirement: moderate, can survive drought once established
Sun requirement: full-sun (acceptable) to part-shade (preferred)

Cones (male): Cylindrical, pale brown, 15-40 centimeters in length and 6-10 centimeters in diameter
Cones (female): Globose/ovular, up to 12 inches long, rare in cultivation (unfertilized cones grow 20-35 centimeters long, 12-20 centimeters wide, and are pale grey)
Leaves: The palm-like leaves are 3-6 feet long with up to 160 leaflets per leaf “stalk”. The leaflets are lanceolate (lance-shaped), pointy, and up to 5 inches long. The leaves and leaflets range from grayish-green to bluish-green.
Seeds require stratification: “warm stratification” helps with germination
Monoecious or Dioecious: Dioecious (male and female reproductive organs on one plant)

Notable characteristics:
The Chestnut Dioon produces small offsets (new plants called “pups”) near the base of the plant. These “pups” can be removed to form an entirely new plant (albeit with the same genes). The eggs on the female cone are produced in pairs of two (“Dioon” is a combination of two words meaning “two eggs”)

Uses:
Tropical ornamental, specimen plant. The seeds are edible once cooked, but the infrequency of mature cone production makes this an ineffective source of nutrients. The leaves are sometimes used as floral arrangements, although this practice is illegal in Mexico. Overharvesting cycad leaves without permission heavily damages plants, which is especially unfortunate as some cycads are near-threatened.

Sources used:

cycad_2_mobot2012
D. edule at MoBot

DSC06284
D. edule Form at MoBot

DSC06286
D. edule foliage at Mobot

cycad_2
D. spinulosum at the SIUC Plant Biology Greenhouse

All of the images provided were taken by me. They may be used for educational or informational purposes if appropriately cited first.

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