Rules of irrigation during drought

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By The Staff

All in all it has been a very forgiving season. Plenty of spring and early summer rain has, however, turned into a dry late summer. We are not in the throes of a severe drought but we are in the midst of some unfavorable conditions for newly planted trees, shrubs and perennials.

So, how much is enough when it comes to water? Well it depends on the plant. But one thing is for sure if you have new plantings, get out there and water every three or four days if daytime temperatures are hot; once a week if we stay in the mid-80s. Water is the key component for establishing plants and one day too late can put an already stressed plant at a disadvantage or in the brush pile.

When should we step in where Mother Nature has left off? When you see your plants wilting? Not necessarily. During the summer plants can transpire water through their leaves at a faster rate then they can absorb it through their roots causing wilt. If the ground is moist and water is available to the root system it will begin to recover once evening rolls around. If the plant does not recover by morning, however, then it’s time to water. I’ve read that mature trees can transpire up to 100 gallons of water through their foliage each day. If there is no recovery from wilt with established plant material, this is a good indication of drought-stressed plants. Get water to the plant before leaves begin to shrivel and dry because permanent tissue damage will result. Again, newly planted material should be watered regardless. The less stress the better for the plant for the long-term.

There are several techniques for irrigation and it really depends on what you are watering. A newly planted herbaceous perennial can adequately be cared for by watering at the base of the plant with your watering can. The soil has recently been loosened and the water will penetrate the soil around the roots easily. When it comes to woody plants and trees, however, it is important to get the water to penetrate as deeply as possible.

Shallow watering can create bad growing habits because it forces the plant’s roots to grow towards the surface of the soil in search of the water, this will make them more vulnerable to drying out in the future. When you water woody plants and lawns do so slowly so the water has a chance to seep deep into the soil. The general rule of thumb is that a healthy plant needs an inch of water per week. A deep watering will last longer and will encourage deeper and stronger root growth.

For irrigation a drip system or soaker hose is most advantageous. Drip irrigation puts all the water into the soil, eliminating runoff and evaporation, thus saving substantial amounts of water (estimated at 25 percent to 50 percent). Drip irrigation also keeps water off the foliage of the plant where fungal activity begins. Many homeowners with automatic sprinklers should only use them once a week. All that spraying water can cause an increased incidence of fungal diseases, crown root and limited root growth if too much water is applied in a shallow fashion.

Mulching or composting around plants also helps in maintaining the moisture content of the soil and keeps down weeds that compete for moisture. Applying two inches of mulch is recommended, but be sure to keep it pulled away from the crowns of plants and the trunks of trees. Don’t over mulch because this causes roots to grow towards the surface in search of oxygen. Feeder roots that have grown into mulch mounds will dry out more quickly then roots that are down in the soil where they are supposed to be.