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The Garden Guru: Always more to learn about watering

Posted Saturday, Jul. 28, 2012

By Neil Sperry

Special to the Star-Telegram

I have written several times about the tools and techniques of watering. It is, after all, a critical part of summertime gardening in Texas. However, as I was helping a friend, I realized that the factoid I was sharing with her had never shown up here. I grabbed a pencil, and jotted down several others. I'll present them as they are asked of me.

Why do bluegrass and lilacs do poorly in Texas?

It's a simple matter of withdrawals versus deposits. Plants that prefer a cooler climate use up their stored food reserves faster just trying to stay alive than they are able to replenish. While those plants don't necessarily scorch and burn, they grow lethargically, often fading away in the process. We need to choose plants that can keep producing sugars via photosynthesis, even in our Texas summer temperatures, and that's why subtropical Bermuda and St. Augustine grasses are better here than bluegrass, and it's why crape myrtles are better here than lilacs.

Did I overwater my plant?

I hear it all the time, and the damage I see is almost never from plants having been kept too wet. To the contrary, it's almost always because they were allowed to get too dry at least once. There are a couple of telltale symptoms of plants that have been overwatered. First, they will be wilted, even though the soil is moist, and that will even be the case early in the morning, before the sun really hits them. Second, the soil will be soured (foul-smelling), and it will probably have moss or algae growing on it. If you're not seeing one or both of those things happening, your plant probably just got too dry.

Why are my plant's leaves browned around their edges?

We can compare plants to the human body for this answer. Just as circulatory problems in our bodies are manifested at our extremities (fingertips, ear lobes, tip of the nose, etc.), the edges and tips of plants' leaves are farthest from the roots. They're the first places to dry out, and they're the last places that receive water as it's being pulled up through the plants. This sort of browning, however, can stem from several causes. The obvious one is that the plant got too dry. You might have applied too much fertilizer, or hot and drying winds might have been involved. It could be due to roots lost during transplanting, or there could be stem damage. It might even be that a shade-loving plant is receiving too much sunlight.

Are polymer gels of use in the garden?

These are the granulated, water-absorbing products that are added to garden soils and potting mixes to improve moisture retention. Obviously, that concept would seem to have merit, and they are used in several commercial potting soils. However, in the landscape and garden, they're expensive and tend to hold too much water when we run into extended rainy spells. It's just a personal opinion, but adding organic matter has always made a lot more sense than the gels when it comes to improving native North Texas soils.

How long will my plants show effects of last year's drought?

That's a question that is coming up often, and the answer will vary by plant. You can already do a complete assessment on turfgrass, perennials and groundcovers. Most shrubs that were hurt will also be showing the full extent of their injury by now. However, large trees may continue to decline for a year or two, perhaps longer. The effects of bad weather linger longer in lumber.

Is it better to water for one long, soaking cycle or for several shorter intervals?

If you have sandy soil and flat terrain, it will make no difference. However, if you have an impenetrable clay, and especially if that clay is on a slope, it's far better to water for short bursts, wait 20 or 30 minutes, then water for another short burst. In fact, that's one of the main principles behind "smart" controllers for sprinkler systems. You program the soil type and degree of slope (as well as plant type, amount of sun, etc.), and the controller determines the rest. Several stations in my sprinkler system run only a minute or two, and they actually will rotate through 10 or 12 run cycles each time the system calls for irrigation. Not one drop runs off in the process. That's better for my plants, and it's a responsible way to conserve water.

Neil Sperry publishes "Gardens" magazine and hosts Texas Gardening 8-11 a.m. Sundays on WBAP AM/FM. Reach him during those hours at 800-288-9227 or 214-787-1820.

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