Dogwood FAQ

Should I plant flowering dogwoods? I have heard that dogwood anthracnose is devastating dogwoods and that none of them are resistant to this disease.

The native flowering dogwood is still a valuable landscape tree and is worthy of planting in the right spot. Dogwood anthracnose is caused by a fungus, Discula destructiva, that thrives in rainy, cool spring weather. A quick warmup in spring will stop the fungus in its tracks. If you plant your dogwood in a location that gets morning sun and good air circulation, it is much less likely to succumb to this disease. Dogwoods are shallow rooted and benefit greatly from some extra water in times of drought; trees stressed by drought are much more likely to be damaged by dogwood anthracnose than trees grown with ample soil moisture. It's also a good idea to remove watersprouts that grow on the trunk and large branches the fungus can use these succulent stems to travel quickly from the leaves to the inner bark, where it kills the living cambium tissue. If the fungus reaches a major branch or the trunk, it can kill the living inner bark, resulting in death of the entire tree.

I recently planted a new dogwood tree. It seemed healthy when I bought it, but the leaves soon took on a grayish white cast and puckered. What should I do?

In recent years dogwood powdery mildew has become a major threat to dogwoods. The most notable symptom of powdery mildew is a powdery white film on the leaves; usually the leaves are distorted and growth is diminished by the powdery mildew fungus. Fortunately many fungicides such as neem and horticultural oil are quite effective in controlling mildew and are not as toxic as conventional chemical fungicides. Foliage should be treated as soon as it has fully expanded to prevent the infection of powdery mildew. Repeat applications may be needed to protect the foliage from mildew through the growing season.

Don't the flowers of the native flowering dogwood, Cornus florida, grow singly?

No. The tiny yellow flowers are actually clustered tightly together in the middle of the four showy bracts. While the whole thing looks like a flower with four petals and golden stamens in the middle, it is correctly referred to as an inflorescence, which is a botanical term for a flower cluster. The bracts attract pollinating insects to the flowers that lie between them, much as petals attract pollinators to many flowers, but the bracts are modified leaves and cannot be correctly called petals. There may be as many as twenty small flowers sandwiched tightly between the four bracts.

When should I prune my dogwood?

When and how you prune your dogwood depends on what kind of dogwood you have. Shrubby dogwoods that are grown primarily for the colorful bark on the young twigs should be cut back to the ground periodically to remove less attractive older stems and promote the growth of new, colorful stems. The other dogwoods require little pruning. Dead and diseased branches should be removed as soon as they are noticed. You can the thin the branch structure of your dogwood by selectively removing crowded branches at the point where they originate from a larger branch or the trunk. You can also remove low-hanging branches. This kind of pruning, which is done to shape and thin a dogwood, is best done in late winter or early spring before new growth begins. Be very careful not to injure the bark on the trunk; it is thin and easily injured. Injured bark provides an easy entry point for dogwood borer larvae.

Can I eat the red fruits of dogwoods?

Some dogwoods produce larger fruits than others, and some are tasty and some are not. The fruits of our native flowering dogwood, Cornus florida, are not poisonous, but they do not have a very pleasing flavor. The Chinese dogwood, Cornus kousa, has spherical fruits about the size of a quarter. When ripe in midsummer, they turn coral red and develop their full flavor and sweetness, with a flavor comparable to some melons. The cornelian cherry, Cornus mas, produces a tart, elongated fruit with a hard pit in the middle and a thin layer of flesh. These bright red fruits are sometimes used to make preserves, jam, or jelly with a flavor similar to cherries.

I want to plant some dogwoods in my yard. They are common in the woodlands near my home-can't I just transplant some into my yard to save some money?

While dogwoods can be transplanted, it is difficult to transplant trees of any size from the wild. Dogwoods have shallow, far-reaching root systems, and it is difficult to get enough roots when digging a dogwood to sustain it while it is getting established in its new home. If you do get a large enough root ball, you will have disturbed a large spot in your local forest, which amounts to an invitation for woody weeds that may spread and degrade a woodland once they have gained a foothold. Another problem lies in the fact that dogwoods do not easily adapt to wide variations in light conditions. A tree that grew in the understory of the forest will most likely suffer greatly if moved into increased sunlight. Purchase a small dogwood from your favorite nursery or collect a few seeds from the dogwoods and start your own trees. Plant the seeds after removing the thin layer of pulp and place them in a pot with free-draining potting soil, water it well, and leave the seeds outdoors where they can be exposed to winter's cold. With some patience, the seeds should sprout sometime in the following growing season. They can be potted into progressively larger pots, or they can be planted directly where they are to grow.

I have some redosier dogwoods that I planted several years ago. They were beautiful for several years, but now they produce fewer red twigs. Is there anything that I can do to increase the production of red twigs?

Chop the plants back to the ground. Like most shrubby dogwoods, the redosier dogwood is perfectly adapted to severe pruning. In their native habitat, redosier is a food source for beavers and it responds to severe pruning by sending out a vigorous new flush of growth. If not pruned back every three or four years, redosier dogwood develops gray bark that is not nearly as striking as the bark on younger twigs.

Related topic: Flowering Dogwood

Source:
U.S. National Arboretum