Fall has arrived and there’s still plenty to do in the garden. If you’ve got questions, turn to Ask an Expert, an online question-and-answer tool from Oregon State University’s Extension Service. OSU Extension faculty and Master Gardeners reply to queries within two business days, usually less. To ask a question, simply go to the OSU Extension website and type in a question and the county where you live. Here are some questions asked by other gardeners. What’s yours?
Q: One of my two large white oaks has lost most of its leaves, the other is only beginning to see color change. Wondering if the one losing leaves is diseased. – Jackson County
A: If the soil under your oak 12 to 18 inches down is dry and crumbly, the oak is out of water. A deep watering will invigorate the drought-stressed tree. Perhaps it seems ill-advised to water an oak tree during a drought. But think about it a minute. If you lose the oak, you lose substantial aesthetic and property values. Also lost are the many ecosystem services provided by this “keystone” structure, such as shade, soil nutrients, wildlife habitat and biodiversity. These take a very long time to replace.
Deep watering of the drought-stressed tree is accomplished by moving a hose under the canopy of the tree during the day for one or two days at a low flow or trickle, such that the water percolates into the soil. Do this once or twice during the summer to early fall with at least a month between watering to allow the soil to dry, reducing the likelihood that fungi will attack the tree roots.
As long as our hot droughty conditions persist it would be good to give your tree a good watering on all sides. As soon as the fall rains begin, let off until next year.
A prudent approach to the current drought and the maintenance of tree health is to conserve existing soil moisture as much as possible. Mulching under the tree helps to control moisture by keeping the soil cool and suppressing weed growth. Mulching also adds valuable soil microorganisms.
Signs of drought will be most visible in the foliage of trees. Look for the following symptoms in times of short-term drought.
- Temporary wilting. Wilting and drooping leaves will occur during the day. Leaves will recover and appear normal by morning.
- Permanent wilting: As droughts progress, leaves will remain wilted even in the early morning.
- Yellowing Leaves: Prior to dropping foliage, leaves will turn yellow and exhibit fall color.
- Leaf scorch: Leaf margins will have a brown or burned appearance.
- Defoliating trees: Trees will generally begin to lose their leaves from the top and branch ends.
Q: I’m seeing an abundance of craneflies the last few days on my lawn. I’ve never seen quite this many before. Is there anything I can do now as a preemptive strike against all of the larvae? I definitely don’t want to harm the bees are other beneficial insects. – Lane County
A: There is no correlation between adults flying around and damage to lawns (as you…