Q. We have used 20% vinegar to kill weeds and Bermuda grass and it works well. We have raised rose beds that have Bermuda growing in them. If we use the vinegar will it hurt the roses? – B.F., Dallas
A. No, unless it is overused. Make sure you buy the kind that is distilled from grain alcohol. Do not buy the kind that is made from 99% acetic acid which is a petroleum derivative. Also, you can save money and have better results if you use 10% vinegar and add 1 ounce of orange oil and 1 teaspoon of liquid soap per gallon. No water should be used in the mix.
Q. How does making a flower planting box around the trunk of a tree harm the tree, and what are the symptoms of the harm it might be causing? – R.E.B., Dallas
A. If it is a small bed that only covers a small percentage of the root zone, the damage is limited to keeping the bark wet and leading to rot and other diseases. If the bed covers a large portion of the root system, there is the added injury of smothering the feeder roots, causing oxygen deprivation. For the tree's benefit, build no raised beds under trees. If it must be done, limit the area and add little to no additional soil. Keep all soil and mulch off the trunks of trees.
Q. Heard you speak on a chemical that you could put on tree stumps that would literally burn them in the ground. Could you tell me again what the name of that chemical was and where I could get some. – R.W., Dallas
A. You obviously have me mixed up with someone who thinks toxic chemicals are OK to use and harmless to you, the soil, nearby plants and the ground water. I don't believe any of that. There are only three acceptable methods for dealing with stumps. Leave them in the ground to naturally rot away. Hire a tree care company to use a stump grinder to munch them below the soil surface. Death of the stump will be quicker that way. Or, drill holes in the stump, fill the holes with sugar, moisten and cover with a thick layer of mulch. The sugar can be white sugar, molasses, old jellies and jams or any other type you might have.
Q. One of our well-established red oak trees has aphids on every new leaf. How do we treat this? When the leaves turned last fall, they were sooty and moldy looking. Is there a connection? – N.G., Dallas
A. The aphids can be controlled with strong sprays of any of the organic pest control products such as garlic-pepper tea, neem or horticultural oil. Another approach is to spray the tree with two ounces of molasses per gallon of water and then release a bag of lady bugs. These beneficial insects will take care of the situation. Aphids are really not a long term problem usually and will often hit plants when the weather is changing in the spring and fall. If they are persistent it would mean that the tree is in stress due to a bigger problems such as too much or too little water, too much or the wrong kind of fertilizer or being planted too low in the soil. It can also be due to the tree type being ill-adapted to the location. The disease on the leaves indicates that something is amiss. Spray for this symptom with potassium bicarbonate or cornmeal juice. These formulas are on my website http://www.dirtdoctor.com/.