Dear Neil: I planted these Knockout roses two years ago. They did fine for a while, but this year they have struggled. I treated them with a name brand insecticide and fertilized and watered them as well, but with no improvement. They are watered with drip irrigation. Do you have any suggestions?
A: This is not a nutritional problem, nor do I think insects have been involved. I would suspect two things. It could have been black spot fungus. Some of the Knockout varieties are susceptible. If the leaves had large yellow blotches with dark brown spots in their centers, black spot was involved. You would need to spray weekly spring and fall with a labeled fungicide. Second, looking closely at the stems of the plant on the left, I see what look like an unusual number of large thorns. That’s a prime symptom of the fatal rose disease known as rose rosette virus. That disease is spread by a microscopic mite for which we have no control. Knockout roses seem especially vulnerable to it. I wish I had better news if that is the case. Plant pathologists and professional rosarians tell us that we must dig out rosette-infected plants, roots and all, and send them to the landfill.
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Dear Neil: I have weeds that have extremely deep roots growing in my lawn. I prefer not to use chemicals. My neighbors are sending condolences to me. Is digging them out by hand the only remedy?
A: Having a good lawn begins with good lawn care. Regular mowing will discourage most types of weeds, especially broadleaf weeds like the one in your photo. Keeping the lawn properly watered and fertilized also will help. However, when water curtailments arise, we must do the best we can. While I do encourage people to use herbicides prudently, I’ve always made it my policy not to push people beyond their comfort zones. Perhaps spot-treating with a broadleaf weedkiller directly to the weeds and only to the weeds could be a compromise, but you are the one to make that decision.
Dear Neil: What can I plant in a row in my vegetable garden to attract bees and butterflies that will have nectar by mid-April?
A: I’m assuming you want plants that are blooming in mid-April and that attract pollinators, and I’m assuming you want pollinators for your vegetables. Since you didn’t ask for a large assortment of plants, I’m going to stick with just one genus, Salvia. My choice would be autumn sage (Salvia greggii) in all of its colors. It blooms for a long period, starting by late winter and going into the summer, then resuming in fall. It is also a woody perennial, so you can leave it in place year after year. However, there are many other fine salvias that also bloom in spring. Remember that bees travel more than just a few feet. You don’t have to plant immediately beside your vegetables. You could have annuals and perennials that bees like elsewhere in your landscape. Also, there are plants that are pollinated by mechanical agitation (wind or vibration) and not by insects at all. That’s the case for tomatoes. Having a hive of bees right beside a row of tomatoes won’t help their pollination at all. They need to be out in the breeze. Corn needs wind to carry its dusty pollen. Know your crops and how they are pollinated.
Dear Neil: A neighbor planted grape vines that have now grown over onto our property. They are beginning to cover our cedars, pecans and oaks. Will grape vines harm or kill our trees?
A: They could, and they won’t do anything beneficial to your trees. Shade trees require full sun to grow to their best potential, and when vines like grapes or kudzu encroach on the trees’ canopies, it’s only a matter of a couple of years until the trees start to decline rapidly. I would head the grape vines off at your mutual property line.
Dear Neil: We have three healthy Bradford pears that have random dead branches. What causes this?
A: This is fire blight. Many have asked about it in recent years. We didn’t see much of it on ornamental pears until 10 or 15 years ago. Now it’s fairly common. Of course, it’s a huge problem with our fruit-producing pear varieties — limiting with some of the best types like Bartlett, keeping us from growing them in Texas. Prune it out with a long-handled pole pruner. Trim several inches into the healthy wood to be sure you get rid of all of each infection. Disinfect your loppers in a bucket of 10 percent chlorine bleach and 90 percent water between each cut. Next spring spray the trees while they’re in full bloom, using agricultural streptomycin to prevent its entry into the new growth.
Dear Neil: Why would my red oak have dropped leaves spontaneously already this spring? It seems to have stopped now, but I’m puzzled by what would cause otherwise healthy, new leaves to shed. Can a tree have too many leaves?
A: Our pecans have been doing the same thing. In some cases it’s because the leaves have insect galls on them. In other cases there has been enough wind, hail or driving rain to knock them loose. (Parts of Texas would like to get a share of that driving rain.) Sometimes trees do over-produce leaves when we have a cool, moist spring. And birds will sometimes pluck them loose. But the good news is that it’s usually of absolutely no concern.
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