Rare and exotic plants at a botanical garden are suffering "extreme stress" due to the hot weather and drought.

Even plants native to Australia have been withering from lack of water at Kew's country garden at Wakehurst Place near Ardingly.

Now staff are battling hard to save species affected by the high temperatures. Plants are being scorched by the sun and suffering stress from the drought, said the garden's spokesman Trevor Butler.

Among them is the waratah, a small tree which comes from Down Under but has not been able to withstand the heat.

Mr Butler said: "Even a plant that is quite drought-tolerant and is used to being out in a fairly hostile climate is having problems. Its stems should be upright. Instead it is wilting."

Mr Butler said conservationists at the 600-acre estate have been told it could take 100 years to replenish the depleted aquifers beneath the soil.

These are normally relied upon to feed trees at the garden but the water is simply not there.

Mr Butler said: "We are talking about established trees and shrubs with roots that go yards and yards into the ground."

Plants which have been scorched by the sun include hydrangeas, which would usually flower at this time of year.

Wakehurst Place, which receives thousands of visitors every week, can get round hosepipe and sprinkler restrictions because it has its own irrigation system. But it is almost impossible for it to make up the shortfall in rain.

Horticulturalists are trying to conserve as much water as possible with methods such as mulching to reduce evaporation. The mulch is laid thickly around the plants and helps to prevent vital moisture from escaping.

Mr Butler said: "We have had two of the driest winters in decades. Even though May was extremely wet and it seems like we have had lots of rain, in nature's terms we really haven't."

"April was the busiest month for visitors in the history of the botanic gardens which have been run as an extension of Kew Gardens for more than 40 years. We must ensure the beauty is maintained for the peak summer season.

"Even if we use a bowser on every tree affected it's hard for the water to penetrate to the root system where it's needed.

"Our best line of defence is to use a rich, humus mulch which is high in organic matter along with wood chips to keep the moisture in the soil."