Dogwoods surprising in Tri-Cities

KENNEWICK -- The flowering dogwood (Cornus florida) isn't a tree that should thrive in the Tri-Cities.

It's a tree that's native to eastern and central U.S. forests. It's considered an understory tree which means that in its native habitat it grows beneath the canopy of bigger forest trees, such as oak, beech, and maple trees.

Flowering dogwood prefers a cool, moist acidic soil that's fairly high in organic matter. It doesn't tolerate stress, heat or drought well. These don't sound like conditions in Tri-Cities landscapes where soils are slightly to very alkaline. Our local summer sun and heat are intense and stressful on landscape plants, especially flowering dogwoods.

While the flowering dogwood shouldn't grow well here, it does. This week, I saw gorgeous white, pink and dark pink dogwoods in full bloom.

Despite their magnificent show of flowers in the spring, dogwoods do have a tough time growing in our region, especially with the wind, intense summer sun and extreme summer heat.

Toward the end of summer, worried owners of dogwood trees often bring me branches of their sick dogwoods. These trees have developed a problem called "dogwood leaf scorch." The leaves are puckered and partially rolled upwards along the midvein. Usually, the leaves also have developed dry brown tips and margins along with a reddish color. If the scorch is severe, the brown, dry tissues may extend into the leaf area between the veins.

Dogwood leaf scorch is a sign of stress that develops when water is lost from the leaves faster than the tree can replace it. This can be the result of several factors including high heat, windy weather, drought, intense full sun, compacted soil, excess soil moisture, excess salts from fertilization, or a combination of these factors. This leaf scorch problem is common on young and recently planted dogwoods because their roots have not become well established and aren't able to absorb enough water for the trees' needs.

Flowering dogwoods are prone to leaf scorch because they have shallow roots and are adapted to a more moderate climate and partial shade. To minimize dogwood leaf scorch, there are some things that you cando to help your tree. First plant flowering dogwoods where they will be protected from drying winds and hot afternoon sun.

Keep the tree's shallow roots cool and moist, by mulching with bark, being sure to keep the mulch about 6 inches away from the trunk. Water the tree deeply to encourage deep rooting, providing enough water to keep the soil lightly moist, but not excessively wet. With recently planted trees, pay special attention to keeping the root ball and surrounding soil moist.

Check to see which varieties are available from your favorite local nursery. Cater to the needs of these tender trees and you'll be rewarded with a spectacular display of flowers every spring and attractive red to purple leaves each fall.

* Marianne Ophardt is a horticulturist for the Washington State University Benton County Extension Office.