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Ask Dr. Hort: Different grasses require different care

Learn the height that is best for your type of grass.

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Learn the height that is best for your type of grass.

Different grasses require different care

Q: I have a question about how short my grass should be cut. My lawn-maintenance guy who mows my lawn says 3 to 4 inches, but it seems too high. All my neighbors have theirs cut much shorter. One guy said it should be cut short this time of year because it is the rainy season. Another guy said that if it is cut too high, thatch will build up. Is that true? Does it matter if it is St. Augustine, Palmetto or Bahia?

A: Knowing your grasses is important, so culture and care is optimized. Bahiagrass is an open growing grass, with few cultivars, that doesn't produce thatch, has tall seed heads and doesn't require irrigation. It should be mowed at 3 1/2 to 4 inches. St. Augustine is a runner grass, with many cultivars, can produce copious amounts of thatch, has short, sterile seed heads and requires irrigation for a quality turf. Dwarf varieties (cultivars) of St. Augustine such as Seville or Delmar should be mowed at 2 to 2 1/2 inches. Standard cultivars such as Floratam, Palmetto or Bitterblue should be mowed at 3 1/2 to 4 inches. The rainy season has no influence on mowing height (other than lawns need to be mowed more frequently), nor does mowing at the correct height cause thatch. Thatch is a natural process like dead fronds on palms (as in a thatched hut). The faster grass grows, the more it thatches. The more you irrigate and the more you fertilize St. Augustine, the faster it thatches.

Turning potting soil rids leaf miners

Q: Do leaf miners live in the soil (I'm using Miracle-Gro potting mix, just purchased this season)? I just cut down my tomato plant, which I had growing in a very large pot because the leaves were covered with the trails from leaf miners. Where do leaf miners come from, and do I need to throw away that whole big pot of soil the tomato plant was growing in? Paula Messina

A: Leaf miners are the larval (maggot) form of tiny flies. They feed, making trails inside the leaf before they exit, falling on the soil or potting mix, where they pupate (rest and then turn back into an adult) to plan their next attack on your tomatoes. By constantly turning your potting mix between crops, the population will be desiccated, so you do not have to throw away your pot. Your tomato can withstand damage on 60 percent its leaves and still produce your bounty, so stay away from chemical pesticides, which are largely ineffective.

Treating Norfolk pine for spider mites

Q: I have a 30-foot Norfolk pine that is turning brown and dropping needles. I suspect that spider mites are the problem. What are your suggestions to save this tree. Raymond Joedicker, Largo

A: You have probably diagnosed the problem on your Norfolk Island Pine, Araucaria excelsa, correctly and I see a couple of options. Spider mites adore a hot, dry climate and evergreens are a favorite target. If the problem is high in the tree, it would be hard for you to safely and effectively get a pesticide to where it is needed. A commercial company would have the right equipment to do the job. If the area is within the range of a hose end sprayer, apply horticultural oil completely in and around the infected area, following label directions, every five days for three applications. Monitor and repeat with future outbreaks. Rain reduces the population considerably and the rainy season, which we are now in the middle of, will keep the problem in check.

Need help? Dr. Hort (Greg Charles) answers questions about garden problems. E-mail him at or mail questions to HomeLink, Features Department, St. Petersburg Times, P.O. Box 1121, St. Petersburg, FL 33731. Describe problem in full, and include your name, city of residence and contact information. If possible, include a good-quality photo. Fuzzy ones won't do. Photos cannot be returned.

Ask Dr. Hort: Different grasses require different care 08/20/11 [Last modified: Saturday, August 20, 2011 4:31am]
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