Q: We have had five arborvitaes growing and doing well for about seven years, but the one on the end suddenly is starting to turn brown, first on one side, then slowly dying to almost turning completely brown. None of the others have shown any signs of dying. We had some construction earlier this year near the one that is having trouble, could the construction caused this trouble?
S. K. of Collinsville
A: Especially after all the spring rains we have experienced this year, heavy equipment driving over the root zone (anywhere on the edge of a plant’s growth) can crush the roots and compact the soil and kill tiny root hairs. Even though these roots are tiny, they absorb most of the water and nutrients to keep the plant alive. Also the heavy equipment could leave depressions in the soil and collect water. The excess moisture could drown the roots.
At the very first sign of the plant under stress — such as wilting with leaf droop or dying leaves or turning fall color at any time other than fall — be concerned. If the soil is wet, try to drain the surface soil to lower areas. If the soil becomes very hard, you will need to loosen the soil to 10 to 12 inches. A little fertilizer could be lightly sprinkled on the soil surface to encourage new roots to develop.
Q: What is the difference between horticultural oil, dormant oil and superior oil and their use on plants? We have found all three in a garden center.
G. D. of Belleville
A: All three of these oils can be made from vegetable oil or petroleum oil. The words preceding these oils (dormant or superior) are an indication of the time of year they can be used on plants. Dormant means they should be applied when the plants are dormant, such as winter or when the plants are leafless. Superior oil can be applied on plants with green leaves during the growing season. With horticultural oil, you have to read the specific directions on time and application; each one can be very different.
A word of caution — do not use oil at the same time you use sulfur dust as it causes a phytotoxic reaction usually killing your plant. Do not use horticultural oils for at least one month before and one month after applying sulfur. Sulfur is one of the oldest fungal controls used on plants from the days of the ancient Greeks and Romans.
Q: Have you examined any persimmon seeds this fall? If so, what did the seeds reveal about our winter?
K. H. of Fairview Heights
A: I have collected 50 persimmon seeds from around our area and every one, when cut in half, revealed a spoon. I have never had a complete sweep with this persimmon indicator before. According to folklore, this indicates a lot of snow shoveling in our area.
Do it now
- LEAVES: Keep the fallen leaves off your grass, especially when they are wet, to keep them from smothering your grass.