Watering

Grass, just like other green plants, converts energy from sunlight into chemical energy through the process of photosynthesis. Chlorophyll in the leaves of the plant captures light energy and uses it to convert carbon dioxide and water into glucose and oxygen. Glucose is used by the plant for energy, while oxygen is released into the atmosphere. 

Grass plants exchange oxygen, water and carbon dioxide through the stomata on each leaf. When water is scarce, the stomata close to reduce water loss. With the stomata closed, photosynthesis and plant growth no longer take place. The leaves start to curl or wilt to help minimise water loss. If water continues to be unavailable, the leaves will turn brown and die. In a well-established lawn, the roots will still be alive and ready to produce new leaves once water returns.

Watering the grass during dry spells, when there are no restrictions in place, is very much down to personal opinion and preference. If watering is to be carried out during hot weather, when there are no hosepipe bans, it is important to make sure it is done correctly. 

Early signs that water is becoming scarce include a loss of springiness to the grass and a blue-grey tinge to the leaves. This is the time to start watering, before any signs of the grass turning yellow or brown. Early intervention will reduce the overall amount of water needed to keep the lawn healthy throughout the dry period. 

Lawns should be watered thoroughly so the soil is moist to a depth of at least four inches. Soil type and weather will influence how long this will take, but typically watering for an hour will be sufficient. The soil should then be allowed to dry to some extent to facilitate aeration and stimulate root growth. There are no precise rules, but a thorough watering once a week is often enough to keep the grass healthy. In unusually hot conditions and unfavourable soil types this may be increased to twice a week. 

Frequent light watering is counter-productive: the water will not reach the recommended depth and so encourage shallow rooting as well as promoting the growth of moss and weeds. Watering should be carried out in the morning so the grass has time to dry. Watering in the evening can encourage growth of diseases such as red thread and fusarium. 

Incorrect watering can cause more problems with the lawn than leaving it to recover once wet weather returns! 

A well-maintained lawn will have a natural ability to survive dry conditions. Mowing regimes should always take account of the conditions, in hot dry weather the cutting height should be raised, frequency reduced and clippings can be left on the lawn to help reduce water loss.