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Summer Sizzles

July 26, 2012

Summer is a great time for picnics, barbecues and outdoor parties and games.

During this hot summer with drought reaching 21st century highs in many U.S. regions, homeowners enjoying their backyards are also asking a lot of questions about how to care for their landscapes in these extreme conditions.

Here are some of the recent questions Davey tree doctors have been asked through our partnership with American Forests. We hope the answers to these common questions help you as you care for your landscapes this season.

QUESTION: I live in St. Louis, Mo., and I'd like to know if it is OK to trim dogwoods, Japanese maples and red buds during the summer?

ANSWER: You can prune trees at any time of year. Any time you prune, you shouldn't remove more than 25 percent of the tree canopy as a general rule. During the summer months, you shouldn't remove more than 10 percent of the tree canopy as a general rule. Some situations, such as pruning for safety, may alter these percentages a bit for important reasons, but these are typical rules to follow. Click here for more important information about pruning that includes a link to a helpful pruning video.

QUESTION: My crepe myrtle tree has an oil-like dripping all around the base, the leaves are wilting and the trunk has white stuff on it. Can you tell me what it is and what to do with it?

ANSWER: This is most likely an aphid infestation. Aphids, sometimes referred to as plant lice, are small, soft-bodied, sucking insects that feed on tree leaves. They tend to cluster in large colonies on new plant growth. Many aphids leave honeydew in their wake as they feed. This sticky substance is a medium for the growth of black sooty mold fungi and can attract ants, flies and other insects. We recommend you treat the tree with a systemic insecticide containing imidacloprid or acephate as active ingredients.

QUESTION: My tree has a green growth over most of it that is changing the color of the bark. What can I do?

ANSWER: Your description sounds like lichens. They are unique organisms made up of a combination of fungus and algae. The fungus grows on the tree and collects moisture, which the alga needs. The alga creates food from the sun's energy, which feeds the fungus. Lichens on tree bark (greenish-gray patches, typically 1 to 3 inches in diameter) are typically harmless to the tree itself since they do not penetrate or drain life from the tree in any way. They just grow on its surface for support.

QUESTION: I have some black spruce that are about 10 feet tall.  A very strong wind storm came last week and now a couple of the spruce trees have tops that are drooping. Should I let them be, give them support or cut off the tops?

ANSWER: It would be best not to take any drastic measures right now and see how the trees recover on their own. Apply a slow-release, low-burn fertilizer and water to prevent drought stress. If they do not improve and/or begin to pose a safety hazard, then you'll want to talk to a professional arborist about proper pruning to save the tree but also keep it safe for people and structures nearby.

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QUESTION: I have an ash tree that I planted 16 years ago when it was about 3 inches around. It stands about 40 feet high and trunk is about 12 to 14 inches across. The problem is that the bark is splitting and more and more branches are dying. What can I do to help save the tree?

ANSWER: Unfortunately, the symptoms sound like they are a result of the emerald ash borer (EAB). The emerald ash borer is an invasive, wood-boring beetle from Asia that has destroyed millions of ash trees and devastated tree canopy cover throughout the U.S. since it was discovered in 2002. The likelihood of EAB depends on where the tree is located (if it's in an EAB infestation area). For more information on emerald ash borer, visit http://www.davey.com/EAB.

QUESTION: I planted two trees in my yard. One of them has yellow leaves now and some branches have no leaves at all. The trunk is about 4 inches and the tree is about 6 years old. We water them and have bark at the base to hold moisture.

ANSWER: The problem sounds like over or under watering. Both have identical symptoms: yellowing leaves followed by defoliation. Additional symptoms include wilted foliage, a sparse canopy of undersized or off-color leaves, leaf scorch and premature fall coloration.

Dry soil conditions can significantly reduce the lifespan of your valuable landscape trees. A tree suffering drought can even be more susceptible to insect and disease infestation.

Since most of a tree's active roots are within the top 12 inches of soil, a good way to water is to put a sprinkler beneath the tree. Place a soup can close by and run the sprinkler slowly until 2 inches of water has collected in the can. Be sure to water the entire root zone beneath the tree canopy. The best time to water is typically in the morning. Slow, deep watering every five to seven days during drought is ideal for mature trees. For young or newly planted trees, slow, deep watering every three days is a good gauge.

When watering any tree, remember that the soil type and method of water delivery have a big impact on how successful the general recommendations might be. Trees planted on a slope may need some type of soaker hose or drip emitter, as applied water will run off. Sandy soils need shorter watering intervals, and clay soils should have longer intervals. Clay soils are hard to wet, and water will not infiltrate but puddle if applied too quickly. The puddling of water may make one think sufficient water has been applied, but often only the top inch may be wet. The depth to which water has infiltrated the soil must be checked by hand. It is always advisable to physically check soil moisture by hand to a 1-foot depth instead of using watering intervals or relying upon automatic timers.

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