Horticulture: July 2006 Other Horticulture Articles

In late spring 2006, the National Oceanic and Atmospheric Administration (NOAA) stated the precipitation forecast for Oklahoma during July and August would be "normal" rainfall. As every Okie knows, "normal" summertime conditions are typically hot and dry.

Whether you live in the city or the country, the cost of keeping your garden and landscape watered continues to escalate. To get the most out of your irrigation dollar, consider adopting some of the following moisture management strategies.

With proper management, drip irrigation (above) reduces water loss by up to 60 percent compared to traditional watering methods.

Select drought-tolerant plants when installing or replacing plants in the landscape.
Trees such as golden raintree, bald cypress, fruitless mulberry, bur oak, Osage orange, Chinese pistache and western soapberry are a few trees that tolerate dry locations. Shrubs that tolerate dry conditions include Chinese and yaupon holly, crape myrtle, juniper and nandina. Remember to pay close attention to watering all newly planted trees and shrubs. Contact me, or another Agricultural Division horticulturist, for an extensive list of drought-tolerant plants.

Schedule irrigation based on plant requirements, not calendar date.
Several factors influence plant water requirements, including the age, size and type of plant material. Watering based on a particular day of the month inevitably leads to over-watering young, small-sized plants and under-watering larger, more mature plants. Irrigating based on need is best for the plants and reduces waste, thereby saving money!

Base wetting depth on rooting depth.
Frequent, shallow watering does not encourage deep rooting. Light sprinklings often only wet the soil to a depth of less than 1 inch. Most plant roots go much deeper. When you irrigate turfgrass, wet to a depth of 6 inches. Wet vegetable garden, orchard and landscape plantings even deeper. Depending on the water intake rate of the soil and the delivery rate of your irrigation system, six or more hours might be required to achieve a deep soaking.

To avoid wasting water, match water application rate to the intake rate of the soil.
As a rule, finer-textured clay soils take in water slower than coarse-textured sandy soils. If you experience excessive puddling and/or runoff when operating your in-ground sprinkler system, adjust the system controller to make shorter, more frequent applications. For portable hand-move sprinklers, simply reduce the flow rate.

Use drip irrigation where possible.
Drip irrigation is the water delivery system of choice for your garden and landscape beds. Drip is more efficient than sprinkle because the water is applied at ground level instead of through the air, where much of it is lost to evaporation. Water saved is money saved. There also is less incidence of foliar disease with drip irrigation because the foliage remains dry. If you choose to sprinkle-irrigate, do so during the early morning hours. This allows time for foliage to dry out before nightfall. Also, wind is typically lower during the early morning hours, reducing the amount of water loss caused by evaporation and overspray.

Decreasing the rate of nitrogen fertilizer applied to turfgrass will decrease the growth rate, which in turn reduces the water use rate of the grass.
Applying a slow-release nitrogen fertilizer also will reduce the growth rate of the grass. Because moisture is necessary for roots to utilize mineral nutrients, there is no need to fertilize your lawn during the summer months if you choose not to irrigate.

You can improve the moisture-holding capacity of your garden and flower beds by incorporating organic materials such as compost or peat moss.
Greater water-holding capacity enables you to extend the interval between irrigations. Apply a mulch layer to your landscape plantings and garden. Organic or plastic mulch applied at the base of the plants creates a barrier to evaporation reducing water loss from the soil. Compost-based mulches have an advantage over plastic film mulches because they serve as a slow release source of nutrients upon decomposition.

In case of water rationing, you will need to prioritize what receives irrigation.
Generally speaking, ornamental plantings (flowers, shrubs and vines) are more expensive to install and replace and more prone to drought stress than warm-season lawns and should receive priority when water is in short supply. Don't forget about your trees. Try to give them a good soaking once every two to four weeks.

For more detailed information on moisture management, refer to the publication Efficient Use of Water in the Home Landscape and Garden.

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