Editor’s note: This article is the second in a three-part series on proper watering practices for lawns and gardens. Next week’s article will finish out the series with a discussion of watering vegetable gardens.
One of the many challenges of gardening in the southeast is to know when, how much, and how long to water. The answer to this question varies depending on your soil type, recent weather conditions, and plant species. Last week, Sam Marshall shared tips for properly watering your lawn. This week, I will focus on correct practices for watering landscape beds and plantings.
Water-wise Landscape Design
The southeast is an intense environment for plants, especially if they are not adapted to our climate. Water wise design begins with selecting plants suited for our region and grouping them by their water needs. Some plants are more drought tolerant than others. For example, yaupon, muhly grass, lantana, and crape myrtle can go weeks without rainfall and never miss a beat. Under these same conditions plants like hydrangea, Japanese maple, and most annual flowers will shrivel up and die. Grouping plants with similar water needs and drought tolerance together in beds will help you avoid over-watering some plants and under-watering others.
When to Water
Plants need water to survive but watering too frequently can lead to root and crown diseases. So how do you know when plants in your landscape require water? Let them tell you by showing signs of water stress. The most common sign of water stress is wilting that persists into the evening, rather than just during the heat of the day. When several plants in a landscape bed begin to wilt, you know it is time to water.
Plants need to be watered more often during the heat of summer, particularly those that have recently been planted and have not yet established a deep root system. Planting trees, shrubs and perennials in fall will reduce the amount of extra watering they require their first year by giving them extra time to grow roots before the heat of summer returns.
How to Water
When you water landscape beds, apply water slowly so it can soak deeply into the soil. Soaker hoses, drip irrigation, and micro irrigation systems allow you to do this and are a more efficient way to water landscape plantings because very little moisture is lost through evaporation. In addition, these systems help reduce plant diseases because they apply water directly to the soil and do not wet plant leaves.
Plant roots grow where there is water, air and nutrients. Watering deeply encourages roots to grow deep into the soil, resulting in more drought resilient plants. Frequent, shallow applications of water that do not moisten the top several inches of soil promote shallow, weak root systems. When watering, apply enough water to soak the top foot of soil. Depending on your soil type, this can take anywhere from ½” to 1” of water per application, with heavier amounts usually required for clay soils.
How Much to Water
How long your system needs to run to apply the correct amount of water will depend on the system’s design, soil type, and how dry the soil was to begin with. To determine whether the amount of water being supplied by your watering system is adequate, conduct the following test. Several hours after watering, gently dig a hole six to eight inches deep in the bed. Squeeze soil taken from the bottom of the hole in the palm of your hand. If water drips out between your fingers, you are watering too much; if soil crumbles and falls out of your hand as you open your fingers, you are watering too little. If soil stays together as you open your fingers, you have applied the ideal amount of water.
Just because it has recently rained does not mean your landscape is getting enough water. Summer thunderstorms often dump heavy rains that run off the soil surface into storm drains. When this happens, the soil will be moist to the touch in the first few inches but bone-dry deeper down. This tends to be more of an issue in years when rainfall is infrequent.
To learn more about water-wise landscaping for our area, visit the Lawn and Garden page at http://newhanover.ces.ncsu.edu and scroll down to the section titled ‘Water Conservation for the Lawn and Landscape.’ For lawn and garden advice, visit http://ces.ncsu.edu, where you can post your questions via the ‘Ask an Expert’ link, or find your local Extension office. Make a pledge to save water by taking the 40 gallon challenge at http://www.40gallonchallenge.org/.