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.
Where can I find out more about dogwoods?
If you're interested in dogwoods for your landscape, ask your local nursery
or extension educator for information on those that can be grown in your
area. Rare cultivars with variegated foliage or unusually colored bracts
may be difficult to find; check our Plant
Sources Page for tips on finding a nursery that sells the plant you
are looking for.
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