Dahoon holly (Ilex cassine) is a native Southeastern North American holly that adds color to your garden in the cooler months. A small, low-maintenance broadleaf evergreen tree, it has glossy dark-green leaves that lack the spiny edges found on many hollies. The plant can grow as a large multi-stemmed shrub or small tree trained with one leader to serve as a trunk. Female plants display white flowers in spring, followed by red berries that persist through the winter to attract wildlife. It gladly accepts shaping through hard pruning and has even been used in bonsai culture.
Dahoon holly is normally planted in the cool weather of late fall or early spring as a container-grown nursery plant. This tree has a slow to moderate growth rate, adding 10 to 20 inches of growth per year. The berries of dahoon holly, like many other holly species, contain saponins that are mildly toxic to humans, causing digestive upset if the berries are consumed. The toxicity to dogs, cats, and horses is similarly mild.
|Common Name||Dahoon holly, Cassine holly|
|Botanical Name||Ilex cassine|
|Plant Type||Broadleaf evergreen tree|
|Mature Size||20–30 ft. tall, 10–15 ft. wide|
|Sun Exposure||Full, partial|
|Soil Type||Moist but well-drained|
|Soil pH||Acidic to neutral (5.5–7.0)|
|Bloom Time||Spring to early summer|
|Flower Color||White (female), greenish-white (male)|
|Hardiness Zones||7a–11a (USDA)|
|Native Area||North America (southeastern U.S.)|
|Toxicity||Mildly toxic to humans, cats, dogs, and horses|
Dahoon Holly Care
Dahoon holly does best in a spot with naturally moist soil and plenty of sun. Give it plenty of space to grow, as these trees will spread 12 to 15 feet. If used as a screening hedge, plants can be spaced somewhat closer.
To plant, dig a hole as deep as the container but two to three times wider. Carefully remove the tree from its container and set it in the hole slightly higher than it was in its container. Backfill with native soil, firmly packing to prevent air pockets.
Maintenance is fairly easy for dahoon holly, though you will need to make sure it receives regular moisture. Pruning is not a required maintenance task, though the tree will be more attractive with regular attention.
Dahoon holly thrives in full sun but can be entirely adequate in a partial shade location where it receives two to six hours of direct sunlight daily.
Dahoon holly prefers consistently moist soil, as befits a plant that is naturally found in the swamps, bogs, and damp woodlands of the Gulf Coast from Florida to Texas. It will grow in clay, loam, or sandy soils, but if the soil is naturally dry, the roots require regular watering.
In its native habitat, dahoon holly is found in boggy areas where moisture is a constant presence, so it will grow best if you can mimic those cultural conditions. After planting, cover the soil with two inches of mulch to retain moisture. Water the roots thoroughly during the first year. Be sure to water more often during periods of drought. Without proper watering, the roots will reach for any source of moisture and become stressed.
Temperature and Humidity
Although hardy in zones 7a to 11a, dahoon holly will be best in zones 8 and 9. Zone 7 may call for some winter protection. It has a good tolerance for the extreme humidity levels of coastal regions of 10 and 11, though growth will be somewhat more subdued. It is mildly salt-tolerant.
Dahoon holly doesn't demand regular feeding, but if your soil is alkaline, an annual dose of an acidifying fertilizer may help prevent chlorosis (leaf yellowing).
Types of Dahoon Holly
There is one widely available named cultivar of dahoon holly, 'Angustifolia' that has more narrow leaves. You may have trouble finding this species outside its native growing area in the nursery trade. You may need to contact a local nursery specializing in native species, or order from an online retailer if you want to grow this wonderful plant.
However, dahoon holly is a genetic parent of several more well-known hybrid hollies, including Ilex x. attenuata cultivars 'East Palatka', 'Hume #2', and 'Savannah'. These cultivars may be easier to find than the species form.
Regular pruning is not an essential maintenance task with an established dahoon holly, but like most hollies, it willingly accepts hard pruning if you want to shape it. Pruning will help the tree grow strong and structured. The canopy has a rather open habit creating a drooping effect that makes an effective privacy screen.
Berry-producing evergreen hollies like dahoon are best pruned in the dormant period of late winter so that you don't remove the attractive berries that form during the summer growing season. They can also be pruned in the summer immediately after flowering, but this will remove the current season's berries; if you prune at this time, be prepared for a winter without the bright red berries.
How you prune will depend on the effect you desire, but in general, it's wise to begin by removing any crossing or rubbing branches. If you want a more traditional tree-like effect, competing leaders can be pruned away when the plant is young to favor a central leader to serve as a trunk. If using the plant in a hedge, conclude the pruning session by trimming back the tips of the branches to produce the desired outline.
Propagating Dahoon Holly
Because seed propagation is a slow, difficult process, evergreen hollies are more often propagated by taking stem cutting and rooting them. This, too, can take some time, but it is not difficult; here's how to do it:
- In mid-summer, use sharp pruners to cut segments off the tips of new-growth branches, about three to five inches long. Strip away all but the top three or four leaves.
- Dip the cut ends in rooting hormone, then plant the cuttings in pots filled with a mixture of sand and perlite. Moisten the potting medium, and place the pots inside loosely sealed plastic bags.
- Set the pots in a moderately warm location, 60 to 70 degrees Fahrenheit, in bright indirect light. Inspect the cutting weekly, watering lightly if the growing medium becomes dry.
- When a good system of roots has developed (four to six weeks), remove the plastic bag and set the pot in a bright location, such as a sunny window. In warm-winter regions, the potted cutting can be grown outdoors.
- After a few months, transplant the actively growing cutting into a larger pot filled with ordinary potting mix. Continue to grow the plant in a sunny location through winter, then plant it outdoors when warm spring weather arrives
How to Grow Dahoon Holly From Seed
Hollies are not easy to grow from seed, as the seeds typically require two to three years of dormancy to be viable. Further, the plants are dioecious, meaning that individual plants have male or female flowers, but not both. This means that unless you are growing both male and female plants near each other, the fruit of a female dahoon holly is likely to produce sterile seeds.
If you do want to experiment with seed propagation, peel off the skins of ripe berries in the fall, and break them apart to reveal the seeds inside. Rinse the seeds in cold water and plant them in a large, flat tray filled with standard potting mix. Cover the trays and place them outdoors in a protected area for the winter. You'll need to be very patient, as it can take a full two or three years of repeated winter chill before the seeds germinate and sprout.
When the seeds do finally sprout, carefully transplant the seedlings into individual pots to continue growing. After another year of growing in pots, they should be ready to transplant into the landscape.
Potting and Repotting Dahoon Holly
Though container culture is not common, dahoon is by nature a slender and fairly well-behaved plant that readily accepts pruning. So makes a perfectly good container tree for the patio or deck when planted in a large, heavy, well-draining container filled with a good moisture-retentive potting mix. These plants do not much care for repotting, however, so it's best to choose a large pot right from the start.
Dahoon holly is a fairly common choice for bonsai hobbyists. In this practice, new shoots are constantly clipped off and directed with wires, and the plants undergo frequent root pruning. The plant is carefully removed from its pot to have the roots trimmed. Bonsai practice requires almost daily attention to the plants, so it's for a serious hobbyist or someone willing to become one.
Dahoon holly generally requires no protection against the winter cold, although zone 7 gardeners may find that tenting with burlap during the coldest periods will prevent desiccation and winter burn to the leaves. These trees have relatively thin bark, so young specimens may benefit from shielding the trunk with hardware cloth to prevent rabbits and other creatures from gnawing the bark. Shielding the trunks can also prevent damage from mowers and other mechanical equipment. This protection isn't needed for older trees. In areas with dry winters, make sure to thickly mulch the ground to preserve soil moisture.
Common Pests and Plant Diseases
Aside from pruning, dahoon holly is a virtually maintenance-free plant that rarely suffers from plant diseases. Even verticillium wilt, a fungal disease common to many other hollies, is a stranger to this tree. You may see swelling (twig gall) on the foliage or twigs if the plant is experiencing a fungus infection, but these growths tend to naturally die back and usually don't require treatment.
Insect pests also generally leave dahoon holly alone, with one major exception: This plant is quite susceptible to two-lined spittlebugs, which leave frothy trails of excretion as they feed on leaves. Seriously infested trees may drop leaves. Spittlebugs are fairly easily treated by blasting the leaves with water to dislodge them. Good cleanup beneath the tree will remove eggs and prevent a new infestation.
Occasionally, mites, leaf miners, and scale insects may feed on leaves and stems, but the damage is rarely serious enough to require treatment. Dry conditions are more likely to encourage these pests, and regular watering makes for a healthy plant that resists most pests and diseases.
How to Get Dahoon Holly to Bloom
The white or greenish-white flowers that appear on this tree in late spring are not very showy, so there is no real reason to worry about a holly tree that doesn't bloom—unless you want the red berries that appear after a female tree blooms. If the tree doesn't bloom, it may be a matter of being patient, as a young tree may not produce blossoms (or subsequent fruit) until it is at least three or four years old.
Poorly timed pruning can temporarily interrupt the flower/berry cycle of these plants. If you prune in early spring as new growth is beginning, you'll be clipping off the flower buds and ruining the berry production for that year. It's best to perform pruning operations during the winter dormant season.
If the tree produces spring flowers but not fall berries, you likely have a male tree that will never produce fruit. For growers who want plentiful berries, it's recommended that you grow at least one male tree to help pollinate nearby female trees.
Common Problems With Dahoon Holly
This plant is largely free of the complaints common to other species of holly. But like many acid-loving plants, a holly that grows in soil that is too alkaline may develop chlorosis, a condition where the leaves become yellowed, while the veins show as dark green. The solution here is to lower the soil pH, either through an iron-boosting amendment or by fertilizing the plant with an acidifying fertilizer, such as one formulated for azaleas.
On occasion, the leaves of dahoon holly may develop scorch due to rapid temperature fluctuations in late winter. This doesn't produce any long-term harm; the tree easily recovers.
How is this tree used in the landscape?
This multi-purpose small tree can thrive in metro areas and even grows well along highways. In a residential setting, it is recommended as a small shade tree around patios or to form a pruned hedgerow along a property line. Squirrels and many types of birds are drawn to the red berries of dahoon holly in the fall and winter. Branch cuttings make beautiful centerpieces for the holiday season.
How long does Dahoon holly live?
Dahoon holly is a fairly slow-growing but long-lived tree. In good growing conditions, a holly tree can rival the oak for longevity.
Where does the name "dahoon' come from?
It's thought that the name "dahoon" originates from an early French adaptation of the native Indian word yaupon—the Catawba tribe's word for a particular type of holly used in ceremonial drinks. The French referred to this plant as "houx d'Hon" and over time it became standardized as "dahoon."