Best way to deal with grassburs is by applying a pre-emergent weed killer

Dear Neil: What can we use to avoid sticker plants on property near a lake? When do we treat, and what should we use?

A: There are many plants that produce stickers, burs, prickles, thorns, brambles and all other manners of painful appendages. So without knowing the exact plant, Im taking a bit of a long shot. Usually when that question is asked of me, it refers to grassburs, and the best means of dealing with them is to apply a pre-emergent weed killer, usually granular, before the seeds ever start to germinate. In many part of Texas, that means that you must do so immediately, and for northern areas, a couple of weeks from now. Apply Dimension, Halts or other labeled pre-emergent one to two weeks before the average date of the last killing freeze in your area, and then follow that application with a booster shot exactly three months later. The products are effective for about 100 days, hence the need for the second treatment. Water lightly immediately after you make the application.

Dear Neil: We have a large wasp or hornet nest (size of two basketballs) about 40 feet high in an Arizona ash tree. It is in our backyard, and were wondering if we should take any action against it. Their activity is starting to pick up rapidly with the warming weather.

A: Im never going to win on this answer. My first (noncontroversial) suggestion would be to have a licensed pest elimination company or entomologist identify the insects for you. My tendency is always to leave nature alone unless my family, pets or I are threatened. These things are so high and far away from your home that they will probably coexist with humanity without problems. Ive encountered similar outbreaks in the trees out from our house, and Ive never worried much. Yellow jackets are the one insect that I do not allow to build nests in our landscape. They are too aggressive and unpredictable. But their nests are not large. Control, should it be necessary, is definitely a job for a professional due to the height of the nest. Thats not the complete answer you wanted, but its a good start. Finding out what they are will help a lot.

Dear Neil: Last year we transplanted two Italian cypress trees right next to our in-ground pool. They are 8 feet tall and are doing well, but my wife feels we need to move them again, fearing they could hurt the pool. Its hard work, and Im afraid well damage them. Will they hurt the pool if we leave them there?

A: Italian cypress are not known to have huge, damaging roots, but any plant can cause damage to concrete if its planted too close. These trees, left unpruned, will eventually grow to 35 or 45 feet tall, so you will certainly have huge plants there. Talk to pool people. They will know the strength of the side walls of the pool. Have a landscape contractor in to look at the setting. Right next to ... (to use your term) does scare me, but I dont know if you mean 18 inches of several feet away. There would be a big difference.

Dear Neil: We had JaMur zoysia sod planted three years ago. A sprinkler system went in at the same time. It has all done very well, except for one area about 10 feet by 6 feet. The grass was thin there last fall, and it looks like bare ground there now. I fertilized last fall (18-6-12), and all areas are watered uniformly. There is a tree nearby, but it doesnt seem to shade this area any more than the rest of the yard. We do walk across the area as we go into the house, but its supposed to be able to withstand that. What can we do?

A: Lets try to sort through the facts, the unknowns and anything you can do to get to the cause. Start with the sprinklers. They probably wont be the cause, but theyre easy to check. Turn that station on for a few minutes and watch every head to see if it delivers water uniformly to the area of concern. If that seems to be fine, move on to the shade. In most cases where Im called to a friends home for this kind of troubleshooting, it ends up being excessive shade. Im not saying thats true in your case, but it is in probably 95 percent of the landscapes I visit. There is a threshold of how much light grass must have to survive. Just a few feet can make an hours difference in the amount of shading, therefore in the vigor of the turf. Do the best you can at this early, still-bare time of the growing season, to see if there might be any significant difference. Visit the spot several times over the course of a sunny day to watch the shadow patterns. I would doubt that the foot traffic is the cause. You would have seen paths. You could also do a little probing and digging to see if the soil in that area is the same as in the rest of your lawn. It may have shallow rock. If none of that comes up with a lead, try some more grass this spring. That wont be very expensive, and maybe you can watch it more closely to see what transpires.

If youd like Neils help with your plant question, drop him a note to Gardeners Mailbag, PO Box 864, McKinney, TX 75070 or email your questions to mailbag@sperrygardens.com. Watch here for his reply.

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Best way to deal with grassburs is by applying a pre-emergent weed killer