A Greener View

By Jeff Rugg

February 23, 2016 4 min read

Q: One of my hosta plants has holes in the leaves. What can I do?

A: Hosta leaves are a favorite food of slugs, which are also common pests (with snails) on many perennials, vegetables and trees (like citrus).

Slugs need to stay moist: They hide in mulch and under logs, flowerpots and anything else that hasn't moved in awhile. Check your plants with a flashlight after dark, since they feed at night. They are susceptible to any slug killer or bait available at a local nursery. Wet down the soil in the area before using the killer.

Clean up the area around the infested plants by picking up any boards or logs. Use pot feet to elevate your garden flowerpots and saucers; the slugs will have no moist place to hide.

Try an organic control called diatomaceous earth. Rake the mulch a few inches away from the base of the plants, and sprinkle the powder around the plant's base. It is made from microscopic ocean animals called diatoms -- they are shaped like snowflakes. After they die, the small animals leave behind tiny, sharp-pointed skeletons that the slugs will not glide over.

Bowls of beer can lure slugs to their deaths. Set the bowl in the soil so the edge is at ground level. This may not work if other animals drink the beer first. There is some research that revealed caffeine as a slug killer, so try giving them coffee. I am sure that if you pour hot coffee on slugs, they will definitely die.

Q: We want to trim our trees, but we were told not to cut off any branches in the summertime. Why is that? The weather is warm and we can be outside; we don't want to trim the trees in the winter when it is cold. Is it really better to prune the trees in winter?

A: There are several benefits if trees are not pruned in the summer. First, there is less landscape waste generated without the leaves on the branches. If you chip or shed the branches without the leaves, you can use the chips as mulch; however, with the leaves, you will need to compost the branches before breaking down the leaves.

Every pruning cut creates a wound. To prevent insects and diseases from getting into the tree, wounded tissue must dry up -- the remaining cells need to create a scar tissue that can heal across the wounded area. When the pruning occurs during the winter, the cut wood can dry and the scar tissue may begin forming in the spring, before insects and diseases become available. If the wound is created when the weather is warm, potentially rainy and humid, then bacteria and fungi can infect the open wound.

As you slice the wood, you will smell the fragrance of the fresh wood. Insects can find the wound much more easily; they too can smell the cut wood. Research has shown that insects are attracted to fresh cuts on birch, elm, oak and pines. It wouldn't surprise me to find out the same is true for the emerald ash borer on ash trees.

If insects and diseases are both more likely to attack trees pruned in the growing season than the dormant season, does that mean we shouldn't do any clipping in the summer at all? If possible, I wouldn't trim any of the trees listed above -- the best time to prune small trees and shrubs for the promotion of more flowers is a few months before blooming. Late spring to early summer is the pruning time for crabapples, serviceberry and many others.

Any storm-damaged trees are better off receiving proper care and trimming, instead of letting them sit with large areas of damaged tissue. When dead stems or branches are noticed, they can be pruned off as long as the cut is not on the live branch, just cut the dead tissue.

Jeff Ruggs's weekly column, "A Greener View," can be found at creators.com.

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