Gardening: The heat is on

Droughts have led to the great British lawn being given the chop. But a little TLC is all that's needed to bring back the green, says Michael Leapman

After a bone-dry winter and spring, the future of the great British lawn is under threat again. Surveys show that lawns have been losing popularity over the last few years and that the trend accelerates as each fresh drought turns our verdant showpieces into brown expanses of desert.

The problem will not go away. Scientists say that the effect of the increase in the level of "greenhouse gases", carbon dioxide in particular, could be to increase average temperatures by 3C over the next century and reduce annual rainfall. In these conditions, keeping the lawn looking nice means using precious water. Turning the hose off leaves a dustbowl that would look better covered with gravel or paving - increasingly popular alternatives.

A new demonstration plot, opened last week at the Royal Horticultural Society's Wisley Gardens, is a sign of the times. It has no lawn, just flower beds separated by paving. (It may be no coincidence that the plot is sponsored by Homebase, who sell paving and other hard-landscape features.)

Yet it would be wrong to write off the lawn, reputed to have been introduced to Britain by Henry III more than 750 years ago. The long summer afternoons spent lazing around in deckchairs, watching nonchalant songbirds peck insects from the turf while bees buzz busily in the borders, are part of an image of national contentment that we should not lightly sacrifice.

Some of Britain's most evocative summer pastimes - tennis, cricket, polo, croquet, bowls - depend on a stretch of neatly mown greensward for their appeal. And parents know that children need a friendly surface for playing, and falling over, on.

Terry Ryan, sales and marketing director of the turf company Rolawn, maintains that it is, in any case, a myth to suppose that in paving over the lawn you are saving water. "Lawns help to recycle water because it penetrates through to the water table," he says. "That doesn't happen with a concrete slab. Also, lawns help to cool the atmosphere on a hot day - they're up to 20 per cent cooler than asphalt. More importantly, they absorb carbon dioxide and produce oxygen. Those who advocate concrete and asphalt as being in any way helpful to conserve water, are talking short-sighted nonsense."

The trick is to manage your lawn so that it needs the minimum amount of water, and also to learn not to fret when it dies away in midsummer.

Watering lawns is a contentious topic. Some believe that it is anti-social to do it at all at a time of water shortage - and when hosepipe bans are in force it is, anyway, impossible to do it effectively.

The issue is sure to be high on the agenda next weekend at the RHS's garden at Rosemoor in Devon - newer than Wisley but equally worth a visit. The garden is staging a Lawn Care Weekend and thousands of people are expected to go to pick up tips from visiting experts.

Among the lawn buffs on hand at Rosemoor will be consultants from the Institute of Grounds-manship. Its chairman, Derek Walder, is the high priest of British lawns. He regularly doles out advice at the Chelsea Flower Show and has been helping water authorities draft leaflets for gardeners on how to economise on the precious liquid. "Lawns will always die back in a drought," he says. "It's a self-preservation exercise by the grass plant. Although it may look dead, it isn't, and it will regenerate itself when the rain eventually comes."

A bad drought, though, has an effect on the kind of grass that will survive. The finer grasses, such as fescues, have shallow roots that cannot reach far enough down to take up what water there is. This means that the lawn will be effectively taken over by the coarser and tougher rye grasses. Seed mixtures of grasses that do well in shade, sold by most main suppliers, are usually also resistant to drought, since they are selected to be sown under trees that suck moisture from the surrounding soil.

The only period of a lawn's life when it must have water is just after new turf has been laid or seed sown. That is why Mr Walder advises that new lawns should ideally be laid in the late autumn, when most hosepipe bans will have been lifted. He warns against trying to alleviate the shortage by recycling water from the sink or bath. "You can use washing- up water on flowers and shrubs but not on the lawn. The residue of detergent harms the grass by leaving a viscous coating."

A browning lawn is not only a badge of environmental virtue; another consolation, at least for the idle gardener, is that it does not need to be mown again until the rains restore it. When mowing early in the season, if you fear that drought is imminent, set the blades of the mower higher than normal, leaving at least three-quarters of an inch growth above the soil. This will actually help the grass to cope better with the lack of water.

Weeds are the toughest plants around and, with their long root systems, will survive drought better than grass. Again, you will just have to tolerate this until conditions improve, because lawn weedkillers are only effective if used on damp soil.

Rolawn, too, will have experts at Rosemoor to give advice. The firm issues an informative manual about lawn care, embracing watering and much else. The first rule is to start watering early, before the lawn has dried out completely - and with luck before the first hosepipe bans come into effect.

Watering should be thorough, but not extravagant, soaking into the roots, which on most lawns are about two centimetres deep. If it gets no further than the surface, the roots will turn upwards to seek it, and in the long run this will make the grass more vulnerable to a drought. Overwatering will deprive the roots of oxygen and cause the grass to die.

There are two ways of telling whether you have watered enough, both involving a penknife. You can dig out a minute hole in the turf and see whether the soil looks moist and dark to the base of the roots; or you can simply slide the penknife into the soil, like an oil dipstick - if it comes out easily and the blade stays clean, the water level is right.

Watering a lawn by hand is a tedious business and not terribly efficient. A sprinkler system is better but beware, on warm days, the higher the arc of the sprinkler, the more water will be lost to evaporation before it reaches the grass. Watering in the evening gives moisture time to penetrate to the roots before being lost to the heat of the day.

Then, when the water boards issue their edicts against hosepipes, you will have the satisfaction of knowing that you have done what you can to prepare the lawn for its ordeal. All that remains is to avert your eyes from the distressing scene and offer up sacrifices to the rain gods.

! Lawn Care Weekend at Rosemoor Garden, Great Torrington, Devon, 26 and 27 April, 10am to 6pm, Admission pounds 3.20, children pounds 1, RHS members free