With the onset of summer in Seattle, at the Magnolia Garden Center we have fielded a lot questions about drought-stressed plants. Here are two of the most recent along with our answers.
Q. My weeping cedar tree is getting brown tips. What should I do?
Q. And the tops of the branches of my new plum tree are drooping in spite of daily watering. What’s wrong?
A: Brown tips of needles or leaves, weeping or wilting young branches or leaves are signs of drought stress. Other signs include powdery mildew on leaves or deciduous tree leaves turning yellow before the fall. All these plants are running short on water. Flowers are usually the first things to get sacrificed, followed by leaves, then fruit and, lastly, branches. Larger plants can tolerate low water better than young or small plants.
The first step for most plants is to water them deeply – a good soaking directly around the plant. Then make sure the plant gets enough water to thrive. Watering correctly sometimes means watering less! Daily watering for plants in the ground is not required in our climate. Most plants will only send out roots as far as needed to find water. If you keep watering the surface frequently, they will only send their roots out and not down deep where water is usually more plentiful. Waiting until the surface soil dries out will force the plant to send roots down deeper. Newly planted trees and shrubs should be watered once or twice a week – but watered deeply: slowly with 10 to 20 gallons using a tree watering bag (sometimes called a treegator), a dripping hose or a soaker-type hose.
A great step is to add mulch (compost or, for trees, bark.) Adding 2 to 4 inches of mulch will help to conserve water by cooling the soil and slowing evaporation. This is probably the single biggest thing to do to promote plant health and ease watering requirements. One note of caution: for more shallowly-rooted plants like Rhododendrons, keep the mulch a few inches away from the trunk to prevent starving the plant of oxygen. This can quickly kill even a large rhody. But give them mulch and some room and they will thrive!