Thames Water said not to water established lawns, water plants during the early morning or early evening mulch over weeds, plant in pots and added: "Your garden centre can recommend plants which need less watering but still keep your garden looking great, such as lavender and bergenia."
The company added: "Planting trees around your garden can reduce the soil and air temperature and the need for watering.
Up to 85,000 litres of rain falls on your roof each year so install a water butt and use it to water your plants and wash your car. Our customers can save up to 50 per cent on water butts by visiting thames.savewater.co.uk
"It has been pretty dry for the last few months (between February and June we have only had two thirds of the rainfall we would expect) so of course groundwater and river levels are dropping.
"Reservoir stocks are currently around 85 per cent, but we never know what the weather will bring more than a couple of weeks ahead and we cannot rely on being able to refill them before the winter.
"It is unlikely that we will need to impose any widespread restrictions on water use this year but we will be monitoring the situation carefully."
Severn Trent Water have said reservoir levels are healthy and gardeners don't need to be in fear of maintaining their plants.
The water company is reporting that reservoirs, which stretch from mid-Wales to Derbyshire, and other water sources are very healthy at an average of 94 percent full and looking good for the summer ahead.
The hottest July day ever saw temperatures of 37 degrees centigrade on 1 July.
Severn Trent water efficiency manager Doug Clarke said: "We all want to keep our gardens looking their best. The temptation is to get the hosepipe or sprinkler out and leave it running. But this approach can use as much as 1,000 litres of drinking water, or 220 gallons, in just one hour. To put it in perspective, that's more water than a family of four would normally use in a whole day! We're urging gardeners not to worry about the health of their lawns – in fact, watering established lawns is not only unnecessary, but can cause many common lawn problems. Watering encourages shallow rooting, which in turn means the lawn is more at risk in dry conditions. So once you start watering, you can't stop."
Meanwhile, a Met Office report published in Nature Climate Change says nine iut of 10 sumemrs by 2100 will be "very hot" and "very cold" winters will be almost non-existent.