Water is essential to all life… too little water and we die, too much and we drown. The same is true for the grass in our lawns. Water makes up 70% to 80% of the weight of our lawn grasses, and clippings are nearly 90% water. While most people are concerned about not watering their lawns enough, the fact is that more lawns are damaged or destroyed by over-watering.
Watering New Sod
Newly installed turfgrass sod has crucial watering needs. Proper watering immediately after installation will ensure that the turf gets established, and it will also have an impact on how well the lawn continues to flourish for years to come.
Begin watering new sod within a half hour after it is laid on the soil. Apply at least 1” of water so that the soil beneath the turf is wet. Ideally, the soil 3” to 4” below the surface should be moist.
For the next two weeks, keep the below-turf soil surface moist with daily (or more frequent) watering. Pull back a corner of the turf, and push a screwdriver or other sharp tool into the soil. It should push in easily and have moisture along the first 3” or 4”; otherwise, you need to apply more water. Especially hot, dry or windy periods will necessitate increased watering amounts and frequency.
As the turf starts to knit its new roots into the soil, it will be difficult, impossible and/or harmful to pull back a corner to check beneath the turf. You can still use a sharp tool, however, to check moisture depth by pushing it through the turf and into the soil.
Watering Established Turfgrass
The amount of water your lawn receives will determine its overall health, beauty and ability to withstand use and drought. Keep in mind that too much water can ruin a lawn just as quickly as too little.
One inch per week is the standard water requirement for most established lawns; however, this will vary between different turf species and even among cultivars within a species. There will also be varying water requirements for seasonal changes, and still more differences due to different soil types; sandy soils, for instance, dry out more quickly than clay-based soils.
Grass in need of water will have a grey-blue cast to it, rather than a blue-green or green color. Also, on a lawn in need of water, footprints will still be present after a half-hour or more, while footprints on a well-watered lawn will completely disappear within minutes.
Make absolutely certain that water gets to all areas of your new lawn, regardless of the type of irrigation system you use. Many sprinklers easily miss corners and edges, which are particularly vulnerable to drying out faster than the center portion of the lawn. Also, areas near buildings dry out faster because of reflected heat, so they may require more water.
Avoid sprinkling the lawn by hand because doing so cannot provide the necessary uniformity; most people simply do not have the patience, time or “eye” to adequately measure what is being applied across large areas. The only possible exception to this would be the need to syringe (lightly sprinkle) the surface of the grass to cool it in exceptionally hot temperatures or to provide additional water near buildings or other heat-reflecting surfaces.
Water early in the morning, from 6:00 a.m. to 8:00 a.m., to take advantage of the daily start of the grass’s normal growing cycle. Wind speeds are lower at this time of day, so there is considerably less loss of water due to evaporation. Avoid watering at night since prolonged wetness on leaf blades is conducive to the development of turf diseases.
Infrequent and deep watering is preferred to frequent and shallow watering because grass roots will grow only as deeply as their most frequently available water supply reaches. Deeply rooted grass has a larger “soil-water bank” from which to draw moisture, and this will help the grass survive drought or hot weather that rapidly dries out the upper soil layer.
If the temperature approaches 100°F, or high winds are constant for more than half of the day, reduce the temperature of the turf surface by lightly sprinkling the area. This sprinkling does not replace the need for longer, deeper watering, which is even more critical to continue during adverse weather conditions.
During the rest of the growing season, most lawns will grow very well with a maximum total of 1” of water a week, coming either from rain or applied irrigation. This amount of water, properly applied, is all that is required for the health of the grass, as long as it is applied evenly (see below, Ensuring Sprinkler-System Uniformity) and saturates the underlying soil to a depth of 4” to 6”.
Watering Difficult Areas
To achieve a beautiful lawn, watering difficult areas such as slopes and under trees requires some special attention.
When running your sprinkler system, runoff may occur on some soils or sloped areas before the soil is adequately moist. To conserve water and ensure adequate soak-in, turn off the water when runoff begins, wait 30-minutes to an hour, and restart the watering on the same area. Repeat this start-and-stop process, until proper soil moisture is achieved.
Areas under and near trees
If your lawn area includes trees, you need to know the water requirements for the specific trees, as well as for the grass variety. Despite having deep “anchor” roots, trees take up moisture and nutrients from the top 6” of soil, the same area where the grass gets its water. In other words, trees and turf will compete for water. Watering sufficiently for the grass may over-water some varieties of trees and under-water others.
A common solution is to avoid planting grass under the drip line of trees. Instead, use those areas for perennial ground covers, flowerbeds and/or mulched beds.
Ensuring Sprinkler System Uniformity
Irrigation uniformity can be accomplished with a simple and inexpensive method that uses only four to six flat-bottomed, straight-sided cans (tuna fish, cat food, etc.), a ruler and a watch. This measuring method should be used across an entire lawn that has an in-ground irrigation system to assure maximum coverage and uniformity. Follow these steps:
Arrange the cans at random distances away from any sprinkler head (but all within the area you assume is being covered).
Run the sprinkler system for a specific amount of time (say, a half-hour), OR run the water until a specific amount of water is in at least one can (say, 1/2″).
Turn off the water, and measure the amount of water in each can, checking for uniformity. Some variation is expected, but a difference of 10% or more between any two cans must be addressed by adjusting, replacing or relocating the sprinkler head.
Be sure to repeat this test with each sprinkler head in the system.