GARDENER'S MAILBAG

Lichens cause no harm to tree

By Neil Sperry | Published Wednesday, August 15, 2018

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Dear Neil: Over the past 10 years, my 30-foot magnolia has grown thinner and thinner. Now, it has the patches of white growing on its trunk and branches. What causes this, and what can I do about it?

These are lichens, and they’re a tandem growth of algae and fungi. You’ll see the same sorts of lichen growth on boulders in stone yards. They are harmless to the trunk of the tree. As for the thinning, that may be a combination of the really hot, dry summer we’ve had and the several others that we’ve had in the recent past. My suggestion is to apply an all-nitrogen fertilizer to this and other trees in mid-spring, early summer and early fall and to keep it watered deeply.

Dear Neil: We’ve had a nice blueberry bush at our home in the Hill Country for seven years. Because it has trouble with alkaline soils we’ve grown it in a half whiskey barrel and we’ve acidified the soil. It’s given us a nice crop of berries the past two years, but now we have an ant colony in the soil. They boil out every time I water the plant. Is there something I can use that won’t harm the plant?

Those may very well be fire ants. They are especially fond of potting soil. You can certainly use fire ant baits and apply them around existing plants. Talk to your Texas Certified Nursery Professional and read the label carefully. Some of the specific fire ant mound treatments may damage roots.

Dear Neil: My lantana is on my patio with a western exposure. It is blooming and has vigorous new growth, but it has these spots on many of its mature leaves. Is this a fungus? Could I have over-watered it? What can I do to make it look better? I try to use non-toxic materials whenever possible.

I believe it is from the insect, leaf miners. The larvae tunnel inside the surface of the leaves causing lines, spirals and blisters. I would try a systemic insecticide. I respect your comment about non-toxic materials, but there is nothing non-toxic that will kill insects.

Dear Neil: I have this black fungus-like growth in my bermuda lawn. I’ve replanted the entire lawn, but it keeps coming back. As I walk through the grass, it turns my shoes black. What can I do?

That’s bermuda smut. You’ll see smut on other grasses, corn included. It’s harmless to your bermuda. It’s more an annoyance for the mess it can make with your clothes and shoes. Mow frequently so seed heads can’t form and apply an all-nitrogen fertilizer to stimulate new leaves and runners. There is absolutely no need to replant.

Dear Neil: I’m a recent Texas A&M graduate and am new in the commercial lawn care business. I want to do things properly. What is the timing for application of pre-emergents in the fall for winter weeds? I have a large spray tank. Are sprays as effective as granules?

Timing will vary across the state of Texas, but it’s better to be a week too early than a day late. Once weeds are up and growing, pre-emergents won’t do much to stop them. Annual bluegrass is the big issue for winter grassy weeds, although rescuegrass and even rye bother a lot of lawns. As for broadleafed weeds, dandelions, clover, henbit and chickweeds are the worst. Timing would be the last week of August in North Texas and the first week of September in South Texas. “Yes” on the sprays. Work with your supplier. There are commercial products that are not available in the consumer market that will serve your customers very well.

Dear Neil: We have a huge live oak that needs to be pruned. We hired someone to do it for us this month. He said he would be applying pruning sealant, but now we have heard that really hot weather is not a good time to trim trees and that pruning paint is not a good idea either. What are your thoughts?

It sounds like you found a very good arborist. Go with him. Research has found that oak wilt is inactive once temperatures reach their summertime maximums by mid-July. Pruning sealant is always a good idea with oaks to lessen the chances of spreading oak wilt. I do not recommend pruning sealant for trees other than oaks.

Dear Neil: I have grown passion vines in various places in my backyard for years. I get lots of flowers, but I never get any fruit. Why?

Proving a negative is always difficult. They may not be getting pollinated. The plants may not be mature enough. I spent considerable time researching your question online and found a wide range of answers. The one thing they showed me is that you’re not alone. My only advice would be to stay the course. You do occasionally see them bear fruit. Hopefully yours will.

Have a question you’d like Neil to consider? Mail it to him in care of the Wise County Messenger, P.O. Box 149, Decatur, TX 76234 or email him at mailbag@sperrygardens.com. Neil regrets that he cannot reply to questions individually.

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