Watering your lawn

We know that this is a contentious issue with many refusing to water their lawn. It is not always either economical or practical to carry out additional irrigation when the weather turns hot.

It is however worth dispelling a few myths around the subject.

History tells us that, even with the unpredictable weather we have in this country, we will, at some point during our summer, have a period of hot and dry weather. If we are going to water then it is important to do so correctly.

Grass plants lose moisture through their leaves, known as transpiration. Most of this loss is through small holes on the leaf called stomata. When the hot weather arrives, and the soil dries out, and as a last resort, the plant closes these pores to preserve moisture. This stops the plant absorbing oxygen required for photosynthesis and subsequent growth is stalled. The wilt point is reached where the grass, or at least the leaf starts to die, and the parched brown lawn is well on its way.

Other factors that the drying out process can affect are the soils ability to take in moisture. As well as beneficial bacteria and fungi living in the soil there are also some undesirable ones. One such group are called hydrophobins. They secrete a waxy deposit which coat the soil particles and effectively waterproof it. Once this happens the soil cannot readily absorb moisture and you then have a condition known as hydrophobic dry patch. So, even when the rain arrives it is repelled and just runs off into lower lying areas. It can be corrected by aeration and the use of wetting agents which act as a detergent and cleanse the soil.

Prevention is better than cure.

When to water

If additional irrigation is going to be of any use it needs to be done effectively.

Firstly do not wait until the grass has turned brown to start. Once this has happened it is likely that it will take all of autumn and winter to recover. The grass will give off signals when it is stressed. This can be as subtle as a slight change of colour, often a bluish tinge. Watering at this point will correct the situation providing there are no real thatch issues. Using an oscillating sprinkler will deliver the equivalent of around 25mms of rain over a 1 hour period, (dependent on water pressure). Frequent, but minimal applications are not recommended because they do not penetrate far enough to make a difference. So a heavy application once per week will be more useful than several light ones.