Grow Guide: Giving Dogwoods a Leg Up
A stressed-out tree might explain a dogwood death.
Q: I’m particularly fond of my five dogwoods (though I'm still partial to my two Japanese maples). We lost three in one year, as did others in my Atlanta neighborhood. Strange. The survivors are hanging on, though. What could be the problem?
This is a fairly common concern with many trees, but dogwoods in particular.
Though dogwoods are native from New England to Florida (even central Florida, to answer a question from another reader), they are difficult to grow for a lot of gardeners; in fact, it is estimated that only about half the dogwoods planted in any given year will survive at all. And even mature ones are known to “brown out” for no apparent reason.
Rather than blame it on a disease or insects, look instead at the long term damage suffered by dogwood roots when grown in a borderline habitat aggravated by harsh weather.
You may notice that though birds drop dogwood seeds pretty much everywhere, we rarely see mature wild dogwoods growing along fencelines. It’s because, given a choice, they grow best on shaded slopes with rich, deep soil. Dogwood trees have a peculiar root system that has trouble growing well in anything other than well-drained “woodsy” soil.
Sure, many may survive to grow and even have beautiful spring flowers in different habitats. But they will be more susceptible to stresses that other trees can tolerate. Some of those stresses include prolonged drought which can lead to damaged roots, often resulting in limb die-back or death of the trees.
This can be worked around by planting dogwoods in their preferred habitat (light shade, sloped woodsy soil, lots of natural leaf mulch), and in soils more like what they find in nature.
If your garden soil is poorly drained, lacking in organic matter, or otherwise not all that great for dogwoods, it is crucial that you improve it. Dig a wide hole and add compost to the native soil – without overdoing it. Cover the area with a thick layer of natural tree leaf mulch to protect roots and “feed” the soil, and water deeply but not too often the first summer. Once established, dogwoods love a light feeding in the spring and a slow, deep soaking at least once a month during extremely dry summers.
Of course this isn’t always practical, and there are many examples of dogwoods performing beautifully in full sun and heavy soils. But in general, the better you treat a dogwood, the more likely yours will survive and thrive.
Horticulturists often add a special type of beneficial fungus to soils, to help roots grow better through a process called mycorrhiza. The naturally-occurring fungus colonizes plant roots and extends their “reach” by sometimes 20 or more times, while also helping reduce root diseases.
Wild dogwoods find these beneficial fungi quite easily in woodland soils, but home gardens—and the sterile potting soil in which nursery-grown trees are started—usually lack it. Adding it to your soil can have a dramatic effect on tree survival and growth.
You may be able to buy mycorrhizal fungi at a garden center or online, but it is easily found in the soil under wild dogwood. Find a tree that is growing well, dig up a little shallow dirt from underneath, and add it to the soil under your own tree to “inoculate” your tree roots.
Sounds weird, but it works—often just what the doctor ordered for your ailing trees!
No doubt, dogwoods are the queens of spring beauty in the woods, and are favorites for all gardeners. However, there is another stunning native tree that flowers very well at the same time that never fails to impress.
The American fringe tree (Chionanthus virginicus, sometimes called “granddaddy graybeard” or “grancy graybeard”) is a small to medium size tree that is covered in pure white fringe-like flowers, and grows in nearly any kind of soil, sun or shade, with little or no care at all. See if you can locate on at a nearby garden center, or have them order one for you.
And leave the dogwood people to fret and pamper while your fringe tree takes the show with ease and beauty.
Gardening expert and certified wit Felder Rushing answers your questions and lays down some green-wisdom. You can get more of your Felder fix at www.slowgardening.net.