Hornbeam maple is best planted as a nursery container specimen or balled-and-burlapped tree in the fall or spring. It is relatively slow-growing for a maple, taking as much as 20 years to reach 20 feet in height. As the multi-stemmed hornbeam maple matures, it becomes broader, so keep this in mind when positioning your tree. This tree can inhibit the growth of smaller plants, so it isn’t a good choice in an area heavily populated by other species.
Light
Although this tree can do well in partial shade, the best growth—and best fall color—requires full sun.
Soil
The hornbeam maple can cope in a variety of different soil types, as long as they’re moist and well-drained. It can even handle heavy clay conditions. It prefers an acidic soil pH but will tolerate mildly alkaline soil.
Water
Hornbeam maples like a decent amount of water. For best results, keep the soil moist, but not waterlogged. If your soil isn’t great at retaining moisture, you can add some organic mulch around the base of the tree.
Temperature and Humidity
These trees are very cold-hardy and can tolerate harsh winter conditions into zone 4, where temperatures can drop as low as minus 25 degrees Fahrenheit. Although they like sun, hornbeam maple resents excessively dry weather and overly hot temperatures.
Fertilizer
Once established, a hornbeam maple should cope fine without fertilizing—or at most, a light feeding every few years. Young saplings will benefit from feeding with a fertilizer with a decent amount of phosphorous to encourage healthy root development.
Types of Hornbeam Maple
Hornbeam maple is a somewhat rare species that is usually sold in its pure species form. There is one named cultivar, ‘Esveld Select’, that remains in a columnar (fastigiate) form as it matures.
Pruning
How often and how much you prune your hornbeam maple will depend on where it’s positioned and whether it’s being used as a hedging alternative. This slow-growing tree can be left to develop without any pruning (other than to remove dead branches), but the shape will be wider. Late winter or very early spring is the best time to prune these trees. A young tree often has multiple trunk stems; it can be trained as a single-trunk tree by removing all but one of the central leaders. However, this tree can form dozens of stems. If you have one that is more of a bush than a tree with these dozens of stems, it will not be able to be trained to a single leader.
Propagating Hornbeam Maple
It’s possible to reproduce this tree from softwood cuttings, although it can be tricky. Selecting cuttings from young shoots on a mature tree during the summer should see the best results. Here’s how:
How to Grow Hornbeam Maple From Seed
Hornbeam maples are dioecious, with individual trees having male or female flowers, but not both. Therefore, to produce fertile seeds, a female tree will need to be cross-pollinated by a male tree located somewhere nearby. Because hornbeam maple is a somewhat unusual landscape tree, it is quite possible that your tree will produce sterile seeds that can’t be germinated. If you do have both a male and female tree in the area, harvest the seed pods (samaras) from the female tree in the fall, and plant them immediately in pots filled with standard potting mix. Set the pots in a sheltered cold frame for the winter, where they will receive the necessary cold stratification to germinate and sprout the following spring. When working with dried seeds, it’s a good idea to soak them for 24 hours and then stratify them for a few months in cold conditions before sowing them.
Potting and Repotting Hornbeam Maple
Hornbeam maple is not commonly used in container culture, though it is possible to grow them this way, much the way Japanese maple is sometimes grown in large patio containers. Use a heavy, large pot with a diameter at least twice as wide as the tree’s rootball. For a growing medium, ordinary commercial potting soil will suffice. A potted maple tree will require more frequent watering than a landscape tree. Hornbeam maple is a relatively slow-growing maple, but be prepared to prune it regularly to keep it small; taller than 10 feet, and the tree will be susceptible to tipping.
Overwintering
Established trees are cold-hardy and can survive harsh winters with no intervention. Smaller, younger trees can benefit from a thick layer of mulch over the roots for the first few seasons.
Common Pests & Plant Diseases
This tree faces some typical pests, such as aphids and caterpillars. The aphids can be removed with a strong burst of water, and the caterpillars can be removed by hand. For heavy infestations, look to horticultural oil. Horse chestnut scale is a more unique insect for this tree, one that is common in Europe and slowly making its way to the United States. Though it can be unsightly, it does very little damage to the tree. Hornbeam maple might be subject to coral spot, honey fungus, and tar spot, all of which can be treated with fungicides.
Getting Hornbeam Maple to Bloom
The yellow-green flowers that appear in late spring and early summer are not particularly showy, so there is no reason to fret if your hornbeam maple doesn’t bloom. And a non-blooming tree won’t produce the seed clusters that can be rather messy as they drop in the fall.
Common Problems With Hornbeam Maple
Hornbeam maple is a relatively problem-free tree, but you may encounter these issues:
Can’t Find the Tree for Sale
Hornbeam maple is a somewhat unusual landscape tree, so you may need to do some research to find an online or mail-order specialty nursery that offers it. Purchased this way, the tree may arrive as a bare-root specimen.
Leaves Turn Yellow
A hornbeam maple that is planted in soil that is too alkaline may develop chlorosis—a condition in which the plant is unable to extract iron from the soil. This prevents the tissues of the leaves from properly conducting photosynthesis, which causes them to turn yellow as a result. The veins of the leaves often remain dark green, giving the leaves a skeletonized look. Chlorosis can be treated by amending the soil with agricultural sulfur, or by feeding the plant with an acidifying fertilizer. Both methods lower pH and allow the plant to make use of iron in the soil.
Leaves and Branches Die Back
Extended drought can cause wilting and dieback of leaves and branches, but if watering does not solve the problem, you may be facing a more ominous condition, verticillium wilt. The fungal disease attacks the plant’s roots and prevents them from carrying moisture to the top of the tree. The leaves and branch tips may develop a scorched, burned look. There is no cure for verticillium wilt, but you can sometimes nurse a tree through the disease by keeping it well-watered and removing affected branches down to a point where they are healthy.
