Neil Sperry: Angel trumpet, oak leaf hydrangea, oak wilt, aphids on crape myrtles
Updated 1:22 pm, Monday, May 6, 2013
Q. I received two angel trumpet plants, but I've read articles about their being poisonous. What information can you give me?
A. I can confirm that both closely related plants, daturas and brugmansias, are toxic if ingested. However, so are parts of tulip, daffodil and hyacinths, oak acorns, tomato leaves, Carolina jessamine, holly berries, mistletoe berries, oleanders, dieffenbachias, many mushrooms, castor beans and wild onions (last two deadly poisonous) and many other common landscape plants and houseplants.
You need to follow your own heart on this one. From my part, I taught my kids and grandkids not to eat things that weren't put in front of them at the table. I've grown both brugmansias and daturas, and oaks and hollies abound in our landscape. I'm more concerned about electricity, gasoline, texting drivers and a lot of other everyday hazards. But, that's just my feeling. I respect yours as well.
Q. You have mentioned oakleaf hydrangeas here a couple of times. Do they look and grow like regular hydrangeas?
A. No two closely related plants could be much less similar. Oakleaf hydrangeas are large woody shrubs to 6 feet tall and 8 feet wide. Their leaves are star-shaped and as large as dinner plates. They turn crimson red late each fall. In warmer settings, many of the leaves will persist through winter.
Their creamy white floral bracts are about 10 inches long. All hydrangeas need rich planting soils that are kept moist at all times. They do best in total or almost total shade. Plant them where they will receive no sunlight after 8 or 9 in the morning during summer.
Q. I had two large branches cut off a live oak this year. Should the cut wounds be sealed or left to heal on their own?
A. They must be sealed, especially in areas where oak wilt is anywhere within miles. You just don't want to take that chance.
Seal them at once. If you have work done in the future, have those cuts sealed, as well.
Q. One of national stores was selling navel orange trees locally. Will they grow well here?
A. Navel oranges won't tolerate sub-freezing weather for any extended period of time. They may not have told you this at the store, but they were probably being sold as patio plants to be grown in large pots, so they could be rolled indoors when it's cold. You have to decide whether that's an obligation you want to assume. If you have a very protected atrium, or if you're near the coast, your odds improve, but you'll still have to protect them occasionally.
Q. My crape myrtles have been loaded up with aphids the past two summers. They developed black mold on their leaves and twigs. Sprays didn't help much last year. Is there something I can put on them before the insects arrive?
A. Use the systemic insecticide Merit (Imidacloprid) as a soil drench. Apply it in mid-May, and your timing should be perfect. If you wanted to repeat the treatment six weeks later, that should ensure that they don't become a problem again. The black sooty mold develops in the honeydew residue the aphids leave behind. While it's harmless, it is disfiguring, and the soil drench should prevent it.
Q. We have a couple of older post oaks in our yard. They are still showing effects of the drought two years ago. We'd like to help them any way that we can this spring and summer. Suggestions?
A. About the only thing you would want to do is water them if you don't get rain for several weeks. Post oaks seem to resent human invasion. It's common for them to put up with us a few years after we build homes and drives near them, then to die rather suddenly. They are intolerant of grade changes, and they need only occasional supplemental irrigation in areas where they are native. Your best bet would probably to involve a certified arborist in their care. That advice really would apply to any tree issues any of us has.
Q. It seems like we have more weeds than ever this spring. A friend told me last year I was mowing my Bermuda grass too short, so I raised the blade. It looks like I'm mowing at 3 inches. What would you advise?
A. Common Bermuda grass should be cut at 11/4 to 11/2 inch. The dwarf hybrids are usually maintained at heights less than 1 inch. At 3 inches, your grass would be growing vertically, exposing more of the soil to the sun's rays. That would allow weed seeds to sprout and the young plants to develop. My old saying is that "tall grass becomes weak grass." I'd suggest you drop the blade back down soon. You'll end up scalping most of the grass blades off, but Bermuda grows back quickly.
Mail questions to Neil Sperry, c/o Features, San Antonio Express-News, P.O. Box 2171, San Antonio, TX 78297-2171, or email him at SAENgardenQA@ sperrygardens.com.