Application method more important than chemical

Q: We have been trying to kill a tamarisk tree for over a year. One limb has died but the growth on the rest will not stop. We have tried everything from weed and grass killers to painting it, including sealants used when removing a limb. Can you give us any help as we are trying to keep the remaining part of the tree as a decorative piece in the yard?

A: If you kill the tree yourself then you have to use a chemical that has a label for killing trees. You will need to follow the label exactly. If you try to mix it too concentrated, it will not work. You may get dieback but it will not travel through the tree. If you mix it so that it is not concentrated enough, it will not work as well.

There are three basic methods of application you can use. There are several chemicals that will work. The wrong method will make the best chemical not work. The chemical is not as important as the method used to get it inside the tree. All three methods rely on making fresh cuts and immediately applying the chemical in a dilute form and keeping the chemical in contact with living wood for as long as possible.

One is to make downward cuts with a saw or chainsaw through the outer bark and into fresh wood. Do this all around the tree. Paint or spray the chemical into these crevices made by these downward cuts. These cuts act like small reservoirs for keeping chemical in contact with the wood so the tree will absorb as much as possible. Pour enough in so that the fresh cuts will be in constant contact with a wet chemical.

Second is drilling holes into the tree every few inches around the circumference. These holes are deep enough to reach fresh wood inside the tree. Pour, spray or inject the diluted chemical into the holes so that the fresh holes are in constant contact with the poison. The uptake of this chemical is mostly in the wood just under the bark.

The last method is to cut the tree down and immediately apply the chemical to the wet stump. I have used this very effectively on small saplings of tamarisk. If you want to get the chemical deep into the roots, do it in the fall.

Q: My husband and I have lived in Las Vegas for about seven years. We recently had our backyard landscaped. We have a small patch of grass and a raised bed garden. Our garden bed is irrigated with drip sprinklers that we can control, and we were watering twice a day for a couple of minutes. We also covered the bed with a shade canopy to protect it from the hot sun. We get nice morning to afternoon sun.

So over the past few weeks both are grass and garden have been filled with mushrooms. We watered a little less which saved the grass but to our disappointment, our garden has since shriveled up. Not sure if it was from fungus, too much or too little water, or from the hot sun.

A: Most plants perform best in this climate with a little bit of shade, but it should be light shade. If you use shade cloth then it is best not to go beyond about 40 percent shade for vegetables that produce fruit from flowers. Leafy vegetables can go into slightly higher shade levels.

Mushrooms are from decaying organic material like wood shavings or dying roots from trees and shrubs that have been removed. They can also come from soil amendments high in wood particles. It is a natural process and not to be worried about but should be destroyed with a rake when you see them since we do not know if they are poisonous or not. It sounds like your soil is still decomposing.

It sounds like you may have tied your irrigation of the garden to your lawn which is a big no-no if you did that. A few minutes a couple times a day does not sound like much water if you are using drip irrigation. Remember that drip irrigation is measured in gallons per hour, not in minutes.

Gardens need to be watered separately so you can manage your garden’s varying water needs better. I have attached a publication for you to look at regarding vegetable gardening here.

Bob Morris is an associate professor with the University of Nevada Cooperative Extension. Direct gardening questions to the master gardener hot line at 257-5555 or contact Morris by e-mail at morrisr@unce.unr.edu.