Hailing from the coastal region of Mexico around Nuevo Leon, San Luis, and Tamaulipas, Dioon edule (dy-OH-awn ED-yew-lay) is a perennial hailing from prehistoric times.
Its scientific name translates roughly to “two edible eggs”, a reference to the paired seeds it produces. As with other members of the Zamiaceae family, it is dioecious, palm-like cycad, although its leaflets lack the border spines common among its kin.
Dioon edule has a number of common names, thanks to its popularity. These include: chestnut dioon, comb-like leaf, Mexican blue chamal, Mexican cycad, palma de Dolores, palma de Santa Teresita, palma de la virgen (AKA virgin’s palm), and peine.
There are actually two subspecies of the plant, Dioon edule var edule and Dioon edule Angustifolium, both of which are on the verge of becoming endangered.
Dioon Edule Care
Size & Growth
As mentioned, this is a slow-growing plant, but it has the ability to achieve a height of nearly 160’ feet in optimal conditions. It is one of two species in the genus (the other being Dioon spinulosum) to bear growth rings, although these only appear every 20 to 30 years. The trunk itself is fairly thin, measuring approximately 8″ to 20″ inches in diameter.
A cluster of leaves emerge from the summit in a spiral arrangement. This stiff, upright foliage ranges in color from blue green to bright green and may be dull or semi-glossy.
The leaves are flat, measuring 39” to 49” inches long and are oriented in sections with opposing leaflets inserted on the rachis at 180° degrees. Approximately 15 to 150 leathery pinnate leaflets are present, tapering to a sharp point with the basal leaflets reduced into spines.
Flowering and Fragrance
Dioon produces either male and female cones, with the male cones ranging from fusiform to ovoid in shape and being generally smaller at 6” to 16” inches long and 2” to 4” inches in diameter.
They have a pale brown appearance and produce pollen. The female cone, conversely, is a more ovoid 8” to 14” inches long and 5” to 8” inches in diameter, with a pale grey appearance.
Dioon edule seed cones have soft, featherlike scales and can weigh between 2 and 4.5 pounds. Inside are up to 200 nut-sized seeds grouped in pairs which become exposed as the cone unravels.
The seeds themselves mature after a year and are edible. They have an ovoid, white to cream appearance, each measuring 1 to 1.8” inches long and .8 to 1.2” inches wide.
Light & Temperature
While virgin’s palm can survive in full sun when planted outdoors, it absolutely loves partial shade, especially in hotter climates.
The ideal locations to plant outdoors are USDA hardiness zones 9 to 11. This is one of the most cold hardy cycads, being able to tolerate frost conditions down to 10° degrees Fahrenheit for up to four days if mature and well-established.
Watering and Feeding
During the growing season, Dioon edule should receive a moderate amount of water to keep the soil moist, with the plant slowly becoming drought tolerant as it ages.
Reduce watering in winter to just enough to prevent the soil from totally drying out. Try to avoid allowing the leaves to get too wet by ensuring the plant has access to airflow in more humid conditions.
Potted plants will require more frequent watering than freestanding plants.
A fertilizer containing trace elements and equal parts of nitrogen, phosphorus, and potassium works best as a starter. You can use either a slow-release or add liquid fertilizer once per month during the growing season.
Soil & Transplanting
Mexican cycad isn’t very picky when it comes to soil types, so long as it’s moist and has good drainage. Chalky, loamy, or sandy soils all work well. Adding some mulch will help ensure the soil doesn’t dry out too fast in hotter climates.
When transplanting between containers, you should aim for a well-draining potting mix or blend of potting soil and sand. Soils designed for cacti and other succulents are good options.
Never jump sizes when repotting; the plant only needs one container size larger and doesn’t respond to the amount of growth space provided.
Small plants will fare well in pots up to 4” inches, while medium-sized plants enjoy pot sizes up to 5.5” inches before having to upgrade. It should be noted that this plant is very sensitive to air bubbles, so be sure to add plenty of water after transplanting to collapse the soil.
Grooming And Maintenance
This is an extremely low-maintenance plant, able to withstand minor neglect once established.
How To Propagate Virgin’s Palm
You can propagate Dioon edule through either seeds or divide by replanting the pups at the base of an older plant. To grow from seed, you will either need to have both a male and female or procure fresh seeds from a grower.
Surface sow these atop damp sand, and store in an area that remains between 75° and 90° degrees Fahrenheit.
Once the radicle has emerged, move the seedling to aq pot of sandy compost, being careful not to damage the taproot or coralloid roots. Keep the pot in a shaded area away from drafts and feed frequently.
Repot the plant as needed. You may transplant outdoors after about four to eight years once the leaves are in full production.
Dioon edule Main Pest or Disease Problems
This plant is both deer and drought resistant. It can also handle some degree of salt content.
Despite being quite hardy, overwatering can lead to a number of issues, including stem and root rot. It is also susceptible to scale insects, and caterpillars love to munch on its green leaves. Details on How To Stop Caterpillars.
Suggested Dioon Edule Uses
While not commonly seen outside of botanical gardens, Dioon edule’s similarity to palm trees makes it a great substitute in landscapes where the latter has trouble growing. Its increased resistance to cold, disease, and pests also make it an attractive replacement.
The seed pulp is traditionally boiled, roasted, or used for flour in tortillas, while the stem produces a starch commonly called Mexican arrowroot. The seeds have also been used in treating neuralgia.
Owning a Dioone edule is not only helping to preserve this unique plant and provide an attractive point of conversation. It can live for up to 1,500 years, making it a precious family heirloom that will outlast any other material possession.