Practical Care, Watering of Plants During Hot, Dry Conditions

San Antonio Express News
Sunday, July 17, 2005

By Dr. Jerry Parsons

Have you noticed that it has been hot and dry lately? If you haven’t and have not been watering your plants, I imagine that your place resembles the Mohave Desert. Has your water bill reached astronomical proportions? Maybe an evaluation of your watering methods of different plant materials will result in more efficient use of the available water and at the same time reduce the amount you are using.

First check your methods of application. There is no use in applying water any faster than the soil will soak it up. If applied faster than this, the surplus will either run down the curb into the street or else flood out your neighbor. Sandy type soils will usually take water almost as fast as it can be applied but tight, clay soils will take it up very slowly. Select the method of application that best fits your soil. Drip irrigation systems for shrubs makes the most efficient use of water for beds.

Secondly, use a mulch wherever possible. A good mulch conserves moisture, prevents compaction, keeps soil temperature lower, reduces week population and in case weeds do get a start, they are much easier to pull if a mulch has been used. Check the depth of the mulch material. Organic mulches tend to decompose or sometimes wash away, so frequent checks and replacement where necessary will help conserve moisture.

While night-time watering is conducive to development of plant diseases in some environmental conditions, one does get more efficient use of the water in the early morning and late evening when evaporation rates are lowest. Also, as hot as it is during the night in the summer months, watering at night will not be a significant factor in disease development. These best time to water in the summer is after 8 p.m. and before 10 a.m. If you don’t have an automatic watering system, invest in water timers (the Gilmour Mechanical Timer sells in the $10-$12 range) which you can activate when you go to bed and allow the sprinklers to water an area for two hours per setting. Be careful to adjust the spray pattern so it doesn’t water the street! Since we are not functioning under severe water restrictions, you can do this every night — depending on how many hoses and sprinklers you have – until the entire yard is watered.

Last, but by no means least, is the practice of doing a thorough job of watering each time it becomes necessary to irrigate. A thorough watering at 7- to 10-day intervals encourages deep root penetration and full utilization of the available soil moisture. Just because plants happen to wilt during the heat of the day doesn’t mean the soil is dry. If the plants are still wilted the following morning, water that area the next night.

In a home lawn situation management practices have a profound influence on how often irrigation is needed because they affect the growth and development of the plant.

A few examples will illustrate this principle:

Mowing Height – mowing too close for the species will result in a much reduced root system and an open turf. The reduced rooting decreases the “maximum reserve pool of water” while the open turf results in higher evaporation versus transpiration losses. The proper height to mow St. Augustine is 3 inches or the highest setting that the lawnmower allows.

Excessive Nitrogen – applying nitrogen beyond the plant’s needs will cause a decline in rooting and promote excessive leaf growth – more leaves for transpirational losses. This results in transpirational water use beyond the real needs of the plant. In fact, don’t fertilize during periods of no rainfall. Generally, fertilization once in the spring (after mowing the major grass species present at least twice) and in the fall in October is more than enough. If you want to green lawns during the summer, use an iron-containing product such as Iron Plus or Greensand. These are the ONLY two iron products I have tested and found to be effective.

By observing indicator spots that first exhibit wilting – as evidenced by a bluish-green color; foot printing; or rolling, folding,, drooping of leaves, a homeowner can obtain some guidance as to when to irrigate his site. Water “hot spots” or those areas of shallow soil which dry faster than the rest of the lawn by using a water targeting sprinkler. The best for watering those narrow areas along sidewalks or driveways is the green Sprinkler-Soaker Hose (Gilmour is most common brand) on which a low flow rate can be adjusted with the sprinkler side facing upward and then the hose can be flipped to provide a slow soaking without runoff waste. Beware of the black, recycled rubber soaker or sweat hoses-they are soon clogged with the calcium in our hard water and get brittle in direct sun-making them useless.

Don’t water more than you need to but certainly irrigate enough to keep your lawn alive. The lawn may not look lush and green during the summer but if it survives until the fall rains come, you will not lose your entire lawn or have to replace the major portion of the grass. Think survival and maintenance- NOT lushness and golf course beauty.

For more information about the watering of newly established plants; the spring gardening exit plan with fall production in mind; and summer rose, crape myrtle and vitex care, see the 3rd column for July housed at: and titled: “Care and Watering of Lawns, Newly Established Plants, Vegetable Gardens, Roses, Crape Myrtles and Vitex During the Summer.” This common-sense column was written in response to many telephone calls (210-308-8867 or 1-866-308-8867) received on the Sunday from 12:00 p.m. to 2:00 p.m. on KLUP Radio (AM 930) Garden Show after several columns appeared in Saturday’s newspaper. If you have any other questions, do not hesitate to contact me on the Saturday or Sunday Show.

Dr. Jerry Parsons is a Professor for Texas A&M University and a Texas Cooperative Extension Horticulturist for over 30 years in South Central Texas. For more information on this or other horticulture topics, go to and our County Extension website at

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