Ask the Gardener: Praying mantis, tomatoes, crabgrass and shrubs

Posted on: September 7, 2018 | Written By: Doug Oster | Comments

Gardening editor Doug Oster gets asked a lot of questions. A lot. And he doesn’t mind offering gardening advice. But rather than just limiting those answers to the person who asked, we thought it might be a good idea to share that wealth of knowledge with everybody.

There are three ways to send in your questions:

• Email

• Submit your question on our “Your Garden” section of our site

• Send us a message on Facebook.

(The questions may be lightly edited for grammar/clarity/etc.)

• • •

Elaine: In the past week and a half, my butterfly bush has become an all-you-can-eat buffet for praying mantises. The other morning I witnessed a butterfly being eaten. So far I’ve removed five mantis (including a mating pair) and relocated them to other areas in the neighborhood. From what I can tell from the wings found under and around the butterfly bush, so far about 10 monarchs have perished.

Is there anything I can do to keep the mantises out of the bush without hurting them?

Doug: What an interesting problem. Those praying mantis are great for the garden, but they eat both good and bad bugs. I think you’re doing the right thing by moving them to another area of the garden. They’ll find prey in another location and even might fly back to the butterfly bush where the eating is good.

Be vigilant, keep an eye on the butterfly bush and everything will work out. When you see a mantis, gently move it to another part of the garden. I haven’t seen one in my garden for years. I love to watch them, but only when they are after the pests!

• • •

Rosanne: I weeded my flower beds and filled two 50-gallon bags of weeds and old growth. What can I do to keep out the crabgrass now? Some were over four feet long!

Doug: Since crabgrass is an annual, using corn gluten meal to stop the seeds from sprouting is a great way to stop it. It’s applied early in the spring. You can find it at most nurseries.

• • •

Elizabeth: For the second year, my tomato plants have what I call a blight. The leaves turn yellow with brown spots, and continue to wither to dry brown. I pick off the dead, and this year tried to avoid the same spot to plant this year’s plants, but know that I overlapped somewhat. Could you please advise what I can do to prevent this from happening next season?

Doug: Just about everyone had early blight or septoria leaf spot on their tomatoes this year. It’s been a wet one and plants like tomatoes are very susceptible to the diseases. They don’t usually kill the plant, but can slow them down.

This story (read it here) will explain everything you can do next year to avoid the problem.

• • •

Helen: We are looking for a shrub that is fast growing and would only get 15-20 feet high. (Those pesky neighbors can be annoying! Haha!) We did not want a shrub that is jaggy either. Could you recommend something?

Doug: There are a couple of different varieties to look at, but it depends on how bad the deer are in the area. I’m assuming you are thinking evergreen to block the neighbors year round.

Arborvitae is a quick growing evergreen, but the deer love it. Holly would be an option, or evergreen viburnum. Hemlocks will get taller than you want eventually, but are slow growers. If it didn’t have to be evergreen, privets, hibiscus, butterfly bush, deutzia and spirea would also be good.

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