Dear Neil: We have two red oak trees. One has lost quite a few branches, especially in the center. Are they just planted too closely together? What should I do?
A: In landscapes, red oaks should be 35 or 40 feet apart. Therefore, these trees are too close together. Hire a consulting arborist to do the necessary thinning and pruning of limbs so that the trees can co-exist. Oaks grow in forests in situations worse than this and get along just fine. Your arborist will know how to protect the trees against oak wilt.
Dear Neil: I planted a water oak 100 yards from our house, and it’s doing great. Recently I read an article that made it sound like a weed — that its acorns are poisonous and that its trunks are hollow. Should I cut it down?
A: Water oaks require acidic soils, so they are adapted primarily to the eastern third of Texas. I grew up where water oaks thrive, and I love the tree. You need to know that all oak acorns are poisonous, so it’s not just water oak acorns. Also, any species of tree can have a hollow trunk, so you certainly can’t hold that against water oaks. So, the only limiting factor I can think of would be the soil pH. If it’s thriving for you, definitely leave it. Oh, and by the way, some of our other popular plants are also poisonous. Consider the list: daffodils, tulips, tomato leaves, castor beans, oleanders, Carolina jessamine and azaleas, among others (but not poinsettias). We really need to learn not to eat indiscriminately out of our landscapes.
Dear Neil: What is wrong with our lantanas? Their leaves have all turned a strange color.
A: This is damage done by lace bugs, and it began back in mid-summer. Next year, you will want to watch for tiny tan spots to start showing up on the leaves in June or early July. You’ll also see black specks of excrement on the backs of the leaves. As soon as you see the first of those, apply a general-purpose insecticide to control the adult insects, and that should stop your problem for the season.
Dear Neil: I’ve used an iron product as advised on the label, and it hasn’t really helped with this tree. Is there anything else I can do just save it?
A: I wish I knew what type of oak this is and where you are trying to grow it. Many types of oaks must have acidic soils. That list includes water oaks, willow oaks and pin oaks, among many others. Once those trees start growing into alkaline soil, it’s virtually impossible to add enough iron to correct for iron deficiency. On the other hand, sometimes we have new oak trees that suffer sunscald soon after planting. Their trunks split, and the plants can’t take nutrients up properly. Sometimes those trees will heal. I can’t really tell from your photograph.
Dear Neil: We have a very nice 8x8-foot garden. We used a variety of types of organic matter in preparing the soil. One bag that I found in the garage looked rather moldy, and when we had trouble with some of our plants, I found mold in the soil in the garden. Is it possible that the mold in the ground came from the potting soil out of that bag? What can I do to get rid of it?
A: I guess it’s possible that the mold got its start out of the bag, but it would not be anything that would harm the plants. You need to mix additional amendments into the soil. I would use sphagnum peat moss, well-rotted compost, finely ground pine bark mulch and 1 inch of expanded shale. Rototill all of that 12 inches into the existing prepared soil. Give it the winter to mellow, and you should have a wonderful soil mix by spring.
Dear Neil: I am attaching photos of my damaged Texas mountain laurel. Some type of insect is boring holes and killing it. What can I do to save this tree, also hopefully to keep the problem from spreading to my other mountain laurels?
A: I spent half an hour online trying to find the species of borer that attacks Texas mountain laurels. I have seen this damage on several other occasions. Unfortunately, I found no matches on university websites. Borers are typically very difficult to prevent or control. I would suggest that you contact your county Extension office and email a good, clear photograph of any of the larvae you can capture when you cut one of the dead trunks. It’s very possible that there may still be some tunneling around within the wood. Unfortunately, we no longer have preventive sprays available to us at the consumer level. Hopefully an entomology specialist with Texas A&M will be able to identify the species and offer some type of suggestion. I’d be interested in hearing back from you.
Dear Neil: Eighteen months ago, I had 1,000 dwarf mondograss plants set into my front yard between my front walk and the street. However, one area has started to develop browned leaves, and the green leaves are a lighter color. I’m also getting mushrooms in that area but nowhere else. Has it gotten too wet? If a problem is developing, I want to get it as soon as possible. I can’t afford to lose them.
A: I had a similar situation with a bed of almost that same size. My dwarf mondo developed a crown rot that ended up taking about half of my plants. I quickly dug the remaining plants and let them dry for a couple of days before potting them up. Once I was sure they were healthy, I replanted them into an area that had better drainage. This is liriope crown rot, and it is very difficult to control with fungicides. All you can do is to improve the drainage to the best of your ability, and always start with healthy plants. LSU has a really good fact sheet on the disease online.
If you’d like Neil Sperry’s help with a plant question, drop him a note in care of The Eagle, P.O. Box 3000, Bryan, Texas 77805. Or email him at email@example.com.
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