Dioon Edule: Rising Virgin’s Palm

If you’ve vacationed to the eastern coast of Mexico, you probably came across a Dioon edule. Maybe you mistook it for a palm tree or even a fern. What you saw is actually a cycad plant species that’s been around for longer than humans – or even dinosaurs – walked the earth! 

Dioon edule, also called virgin’s palm, is a large, evergreen cycad. Thanks to its subtropical origins, it’s a drought-tolerant plant that’s also delightfully low maintenance. Virgin’s palm is a staple xeriscaping plant in USDA hardiness zones 9-11. It can be grown in the ground, where it’ll stay for hundreds of years, or planted in containers starting at 4 inches wide. 

Like all cycads, dioon edule is a gymnosperm. It grows female and male cones that range from 2-16 inches long. More noticeable is the short, woody trunk that’s topped with a festive fountain of leaves. This plant will definitely add texture and shape to your landscaping. 

In this article, we’ll learn all about the growing habits and cultivation of this collection of native Mexican species. Then, with a warm environment and some patience, you can grow your own!

Quick Care Guide

D. edule leafThe leaf frond of D. edule. Source: amortize

Common Name Virgin’s palm, chestnut dioon, palma de la virgen, Mexican palm, Mexican blue chamal, Mexican fern palm
Scientific Name Dioon edule
Family Zamiaceae
Height & Spread Up to 8 feet tall, 6 feet wide
Light Full sun, partial shade
Soil Well-draining, poor soils
Water Sparse
Pests & Diseases Caterpillar, cycad aulacaspis scale, root rot, fusarium wilt

All About Mexican Cycad

Immature Dioon edule conesWhen immature, the cones are hard to identify as male or female. Source: brewbooks

Dioon edule used to be split into two subspecies: edule and angustifolium. However, the latter was recently reclassified as its own species under the Dioon genus (though the two are still very similar). 

We’ll focus on care requirements for Dioon edule in this article, though they can probably also be applied to D. angustifolium and other species in the Dioon genus, such as Dioon imbricatum, Dioon aculeatum, and Dioon strobilaceum. It’s also worth noting this same species has the synonyms Macrozamia pectinata, Zamia rigida, and Macrozamia littoralis. 

This plant goes by many common names, including chestnut dioon, virgin’s palm, palma de la virgen, Mexican palm, Mexican blue chamal, and Mexican fern palm. As you can tell by some of the names, this plant is often confused with palms. The two are pretty unrelated, as palm trees aren’t even gymnosperms (they produce flowers instead of seed cones).

The most noticeable thing about chestnut dioon is its plume of leaves. These leaves are pinnate, meaning they have a row of opposing leaflets inserted down each side of a central stem (like a fern). As a whole, each leaf grows up to 6 feet long. However, they’re usually in proportion to the trunk and won’t be that big right away.

The semi-glossy, blue-green leaves are very narrow and create a soft look. When they’re young, these basal leaflets are edged with small spines with a sharp point. The bright green leaves sit atop a thick, woody trunk that’s devoid of branches. Below the soil are nitrogen-fixing coralloid roots and a tough taproot that can find water in even the rockiest garden soils.

Dioon edule plants can grow up to 8 feet tall (and they aren’t even the tallest cycads!). However, they grow very slowly, so most cultivated ones are so short that they look more like a bush than a tree in the site they are initially planted. These slow-growing plants aren’t in a rush because they can live for over a thousand years.

With such a long lifespan comes a complicated and somewhat unusual means of reproduction. Dioon edule is a dioecious species, meaning each plant only grows male or female cones. Both plants must be in close proximity to produce viable seed. 

Which sex the plant is isn’t easily known until the female or male cones develop. Even then, they aren’t easily told apart unless compared to each other (the female cones are generally larger). The female cones contain two ovules and produce paired seeds. 

Mexican cycad grows up from the tip with new leaves sprouting from the center, like a succulent’s rosette. Old leaves will eventually fall off from the bottom of the tuft, sometimes leaving a harmless scar on the trunk. Slow-growing female cones will take up residency in the center of the palm-like leaves for a couple of years before releasing their paired seeds.

For an evergreen plant with increasing popularity in gardening, dioon edule is close to becoming an endangered species. Unfortunately, lots of cycad plants are already endangered or on the verge of extinction. 

They are cultivated for their edible (yet toxic) roots in some areas of Mexico. Even though they’re considered edible here, it’s best to avoid eating them. The people who historically use the toxic and edible roots have a deep understanding of the correct ways to process the plant before consumption.   

These magnificent cycads that survived the mass extinction that took out the dinosaurs may not be able to survive the presence of humans. You can help! By growing a dioon edule in your garden or collection of plants, you’re doing your part to preserve this beautiful species.

Chestnut Dioon Care

Dioon edule with coneA dioon edule with its cone. Source: Hi Tech Bio

As long as you provide the optimal conditions, this palm-like plant will be very easy to grow in your garden. Here’s what you need to know for proper dioon edule care.

Sun and Temperature

Mexico palm plants will thrive in full sun. However, since it’s often grown in hotter climates, they appreciate part shade from time to time. If you’re growing it indoors, you must put your dion plants by a sunny window (preferrably south-facing). If your dioon lives outside in the garden among a collection of other plants, place it somewhere with part shade during the hottest part of the day.

Dioon edule hardiness is what sets it apart from other plants in its family. Despite being native to Mexico, this is one of the most cold-hardy cycads, tolerating occasional temperatures as low as 10°F. 

Water and Humidity

Water your dioon plants when the soil starts to dry out. Be very cautious of overwatering your plants, as dioon should never be left sitting in water (especially if it’s planted in part shade). During the winter, when the temperature and growth has dropped, cut back on watering.

Note that chestnut dioon is only drought tolerant when well-established. Don’t neglect a young, newly planted chestnut dioon. When the plant has gotten its bearings, you can go longer stretches without watering. We recommend you don’t go too long though and avoid watering sporadically, as this can stress out any plant.

This Dioon species likes humid conditions, but isn’t reliant on them. Either way, you should ensure that there’s good airflow between the leaves. Give it space in a collection of other plants. When watering, try to keep the foliage and short, stocky trunk as dry as possible.

Soil

Good drainage is perhaps the most important part of dioon edule care. These plants will grow in almost any soil, be it rocky, sandy, or loamy, as long as it drains well. However, any of these well-drained soils also need to hold some moisture. If needed, add some mulch or composted plant material to keep the garden soil from drying out too quickly.

For container evergreen cycad plants, use a soil mix meant for cacti, succulents, or palms. Ensure that the pot has drainage holes and empty the water-catching tray as needed. 

Fertilizing This Slow Growing Plant

Virgin palm female coneThe female virgin palms produce these split “fruit” from the cone. Source: liangjinjian

Dioon edule plants usually grow just fine in poor soils, but their growth will speed up if you provide a collection of some extra nutrients. During the growing months, feed frequently with a lightly-dosed, balanced fertilizer. You can also use sandy compost to boost the garden soil’s fertility.

Pruning

Your dioon edule houseplant doesn’t need to be pruned. You should only remove leaves if they’re diseased or infested with pests.

Propagation

Mexico cycad plants can be propagated by seed, but that would mean procuring both male and female plants, possibly hand pollinating, and waiting until the female cone unravels and releases its seed. Or, to save time and energy, you can buy a new collection of seeds, soak them, and surface sow them right away. Although they take a long time to grow, dioon edule seeds germinate very easily.

If you don’t want to wait so long for an established plant, vegetative propagation is the way to go. A mature Dioon edule plant will produce offshoots at the base of its trunk. Using a sharp, clean knife, cut the “pup” off of the parent plant. If it already has roots of its own, make sure to keep them intact. Plant the cutting in a small container filled with one of the well-drained soils you would use for potted established plants. 

Troubleshooting

Male coneThe male cone slowly opens at its top but remains conical. Source: tatogra

As long as you provide the right garden environment, dioon is one of the easiest plants when it comes to pest and disease problems. There are only a few things to be on the lookout for.

Growing Problems

Like most drought-resistant plants, overwatering is a huge cause for concern. Too much moisture in the soil can quickly lead to root rot which in turn leads to stem and leaf rot. It’s hard for a plant to come back from this, so prevention is key. Before watering, check that the first few inches of the soil is dry first (moisture meters are very handy here). If you accidentally overwater, let the soil dry out for longer than usual before resuming a sparser watering schedule.

Cycads can get sunburned if they get too much sun exposure. Their foliage will turn yellow or pale brown when scorched. This usually happens when the plant is in direct sunlight and the air is dry and hot (we’re talking over 100°F). The damage is usually just aesthetic but can’t be undone. The best you can do for a sunburned cycad is move it to a shadier location in your garden.

If you have a collection of plants that are taller than your Dioon edule, try shading it under them to remedy sunburn. 

Pests

Caterpillars are always hungry for some leaves – especially cycads! To save your dioon’s blue-green leaves from becoming lunch, pick off any caterpillars you see and remove them from the garden. If the problem persists, consider using BT spray or diatomaceous earth.

Dioon edule plants are also vulnerable to scale insects, particularly cycad aulacaspis scale. This unusual, non-native pest was accidentally introduced to the US in the 90s and has been wreaking havoc ever since. They’ll settle into the lower leaves of a cycad plant and feed, turning the leaves yellow and brown. You won’t mistake this for sunburn though because their white bodies are very noticeable.

You’ll need to cut off infested leaves and destroy them far away from your garden. However, these scales may spread to the stem and roots, so you should also apply an insecticide (look for one containing malathion or dimethoate). Of course, the best method is prevention, which is done by only buying healthy cycads from reputable sellers.

Diseases

Your dioon is unlikely to have any disease problems. However, if the roots are rotting from overwatering, they may become infected with bacteria or fungi already in the garden planting site. Fusarium wilt, which comes from a soil-born fungus, sometimes affects D. edule’s cousin Dioon spinulosum. If you see spots of browning leaves or other unusual growths, try applying a general fungicide.

Frequently Asked Questions

Dioon eduleDioon edule is a fascinating cycad. Source: wallygrom

Q: How fast does Dioon edule grow?

A: This is a very slow-growing plant. The short stocky trunk grows so slowly that you’ll usually see this plant at bush height in a garden. These plants live for hundreds of years, so they aren’t in a hurry to sprout up.

Q: Is Dioon edule poisonous?

A: Yes. Though the edible roots have historically been used to make tortillas, the leaves and stems are toxic to humans.

Q: Is Dioon edule sago palm?

A: No, but they’re both in the cycads family. Sago palm can be recognized by its arched leaves, whereas dioon edule plants have flat ones. Sago palm also has a golden-colored female cone while dioon edule’s is white.

Q: How do you plant Dioon edule seedlings?

A: Plant them into what will be their permanent home (if you’re growing them outside in your garden). Gently place them in well-draining soil in a location that’s warm and gets plenty of full sun.

Q: How do you plant Dioon seeds?

A: Soak the hard seeds in water for 1-2 days and then place them on top of the soil in a small container. Keep the seed warm and moist until it germinates and sprouts (you can move it to the garden later).

Q: Are cycads poisonous to cats?

A: Yes, in fact these plants are typically poisonous to all mammals, though they have historically been viewed as edible in certain cultures.

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