When and how much water should you give your lawn during the prevailing hot weather when the thermometer is tipping almost 30 degrees?   We are receiving a lot of calls about the very same subject, mostly about newly renovated lawns with seed or turf.  Sometimes it is best NOT to water your lawn.

Should you water your lawns or not when it is this hot?  Turf grasses are tough old things and so long as you have healthy and desirable turf grasses in your lawns then they should be capable of coping with the extremes of drought.

If you have a newly renovated lawn then the investment needs protecting and the lawn watering daily or every other day to aid establishment of the new lawn. In simplistic terms – droughts happen when it does not rain for a long time. This makes the land dry. Lakes, ponds and rivers run low. People have to use less water when there is a drought to make sure there is enough to drink. Hot countries often suffer droughts. Strange thing is, we are an Island surrounded by water……

The BBC Weather web site details that a drought in the UK used to be defined as 15 consecutive days with less than 0.25mm rain on any one day, but this regimented definition was abandoned in the mid-80’s after running into problems. Different organisations couldn’t decide whether the drought had ended or not, so it seemed easier if each made their own definitions.

It is far more sensible to judge each drought on its own merits…  Not many people mourned for the end of the strict definition, as it was always coming under scrutiny. If after 20 days there is 0.26mm rain, is the drought officially over? If there is less than 0.25mm rain for 30 days is that 2 droughts? It is far more sensible to judge each drought on its own merits and even then it is always hard to determine whether a drought has ended. Hindsight as always is a wonderful thing.

The fuzzy logic of a drought is a bit like a bank account. If you keep emptying it without putting any money back into it, then the source of funds will dry up. If the water loss from a lawn is greater than the water it receives, either naturally via rain or artificially via a lawn sprinkler, then the water and moisture will dry up, like the money in the bank account. Pray for a rain shower, I hear you cry!

We are often aware of the number of days that it has not rained, say in a week, but less aware of the natural evaporation of moisture from the ground and plants including lawns into the atmosphere. See the Water Cylce. The evapo-transpiration rate will increase greatly on warm sunny days in June. A typical lawn will lose around 5mm of water from its surface on a summers day. Attempts of artificially watering with a lawn sprinkler will only replace around 40% of that 5mm naturally lost so you instantly have a water deficit of 60% on day one. Add the water deficit of day two to day one, and day three to days one and two and you get the picture.

This is why it is just not worth attempting to water your lawn during a period of drought or semi drought because you will never keep up with the natural water loss/deficit and the lawn will gradually turn brown it it’s attempt to conserve water at the roots and crown of the plant to survive when the rains come. On sunny days with lots of wind, even if the air temperature is not really high, the water loss form the lawns’ surface will still be great which is why you could potentially need to water a lawn in April or May, especially typical of this year.

Turf grasses typically turn brown in dry weather a bit like the leaves on an Oak Tree becoming sticky in the summer to conserve natural water loss from the leaves during the process of evapo-transpiration. Patches of weed grasses such as Annual Meadow Grass, Couch Grass, Colts Foot, Creeping Soft Grass, Yorkshire Fog, Brome Grass to name a few react violently to a slight change in climatic conditions such as periods of drought like conditions and go brown quicker than proper turf grasses used in turf production and lawns.

Our advice is to make sure that if you know it is going to be dry, kill the weeds and moss in the lawn as they take up valuable water in plenty of time for summer, fertilise your lawn in readiness of the summer weather and raise the height of cut of the mower to prevent maximum water loss. Take a look around as you go about your business. Peer over your Neighbours’ hedges and you will see that the lawns that are not fertilised, full of weeds, mown too short are already almost brown. The healthy lawns will always look better and greener during a dry patch and the lawns that are not out in the full sun of the day too.

If you do need to water your lawns, little and often and check how effective you are actually watering your lawn by getting the gardening knife or penknife out and having a little dig in the soil to see how moist to a depth it is.

As soon as the rains arrive, wait a couple of days then top the lawn on a high mower setting and fertilise it with a good quality lawn fertiliser to get it back up to speed again.  Control any weeds that always appear to do really well during a dry spell, in particular the Clovers and Trefoils.

The use of Wetting Agents is a good practice as they break down the surface tension of water top make water wetter.

Keep tracks on the weather forecast by visiting The Met Office