Gardening

Gardeners Q&As for August

By Dr. William M. Johnson
Galveston County Extension Agent - Horticulture

Hydrangeas require full sun and adequate moisture for best bloom. Photo by William M. Johnson

Question: I have some large, healthy hydrangeas that refuse to bloom other than perhaps one large bloom per year. Any ideas on what the trouble might be?

Answer: Hydrangeas require full sun and adequate moisture for best bloom. If you are meeting these needs, the only other obvious cause of lack of bloom is improperly timed pruning. Prune the plants immediately after bloom, so that new growth will be able to develop flower buds in the fall. Pruning in the spring or early summer removes the fall developed flower buds and will reduce or prevent blooms for that year.

Question: When my air conditioner unit started running overtime, I called an AC service company to check it out. The repairman told me that the cooling coils on my outside AC unit were clogged with cotton produced by cottonwood trees. I’ve noticed that some cottonwood trees produce lots of cotton while others do not have any cotton. Why does this happen?

Answer: If you have cottonwood trees growing in the neighborhood, you should periodically inspect the coil fins of your outside AC unit for blockage by cotton produced by female trees. Many people do not realize that there are male plants and female plants in some plant families. Such plants, including cottonwood trees, are called dioecious.

Male cottonwood trees produce pollen, while the female trees produce an abundance of seeds which are surrounded by ultra-light white fluff hairs that look like cotton. The "cotton" is an appendage to help disperse the cottonwood seeds so they do not fall at the base of the mother tree.

As seeds drop from the parent tree, they are carried by wind away from the mother tree. In fact, the tree seed that often stays in flight the longest is that of the cottonwood. The tiny seeds can be carried by air currents from anywhere between a minute and to a couple of days. Unfortunately for us city dwellers who are creatures of comfort, the cottony-like seeds of cottonwood often end up clogging the coil fins of our central AC units.

Be sure to keep the outdoor condensing unit free of cottonwood seeds as well as grass clippings and dirt buildup. Sufficient air cannot pass over the outdoor coil for proper cooling operation if it is clogged, which causes the unit to run longer and work harder. The cooling coils can be easily washed down with a garden hose, but shut off power to the unit before you do so. Cottonwood seeds can also clog car radiators and window AC units.

Question: There are large insects that look like bumble bees that are chewing holes under the eaves of our outbuilding. What can I spray on them to keep them away?

Answer: It is the season for the carpenter bees which are very similar in appearance to bumble bees. The female of this species is responsible for the boring of the wood as she makes her nest. There will be only one bee per hole. She will lay her eggs inside this tunnel.

Because a carpenter bee does not eat the wood she is boring through, it is difficult to stop her with surface applications of insecticides. There are no repellents sold for this purpose. Once a tunnel has been bored, you can spray or dust with Sevin. When the bee enters and exits the hole, hopefully some Sevin will get on her body and she will ingest it when she grooms herself. Wasp and hornet spray can also be sprayed into the hole.

Question: We have just spent a lot of money on several loads of hardwood mulch to go around our shrubs. It has only been down for about 3 weeks when orange and yellow mounds appeared in it. It looks like some type of disease because it is coming up in the middle of our flowers. What can I spray to stop its growth?

Answer: With our unusually rainy weather over the last few weeks, this has been a frequent complaint. This growth is a slime mold which is a primitive type of fungus. It is harmless to plants. Although quite unattractive and somewhat alarming, it will dry up in just a few days. You can hasten its demise by disturbing the mound with a rake. This fungus is associated with the decomposition of hardwood bark. As the bark ages over the summer, you will see less of it. I know of no fungicides that would effectively control this mold.

Question: These recent thunderstorms continually break limbs out our trees. I am afraid it is just a matter of time before one hits the house or a car. I really think some of my trees need to be pruned, but I don't want to wait until winter. Is it safe to have trees pruned now?

Answer: I strongly recommend that most landscape trees be pruned during the winter season. Pruning trees in early summer is not recommended unless there is a real need to do so such as limbs being damaged by wind or storms. Dead limbs should also be removed.

Have the tree checked for soundness or the presence of decay. These are often the ones that blow down during summer storms. The degree of decay will determine whether the tree stays or should be removed.

Simply filling a tree cavity with concrete does not make the problem go away regardless how well someone cleaned it out. I cannot stress enough the importance of periodic examination of large shade trees for structural defects, decay, and other health problems. Preventive maintenance will only save you money, inconvenience, and possibly bodily injury to you or a loved one.

Question: Is it true you can eat the blossoms of squash?

Answer: Yes you can. I have eaten them after they were washed, dipped in batter and fried.

Dr. Johnson is a horticulturist with the Galveston County
Extension Office of Texas Cooperative Extension, Texas A&M University. Visit his web site at http://aggie-horticulture.tamu.edu/galveston/index.htm

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