Embattled gardening businesses have been granted a 28-day reprieve from the hosepipe ban.
Water companies moved to relax the rules following the wettest April on record which boosted river flows and eased the severity of the drought.
Thames Water said landscaping, turf and gardening firms in the South and East of England could now return to using hosepipes on newly laid turf and plants for a four-week period.
The decision was welcomed by horticultural businesses who feared the restrictions could lead to the loss of contracts and jobs.
Thames Water said about two-and-a-half times the normal amount of rain has fallen since it imposed a hosepipe ban on April 5.
Richard Aylard, the company's sustainability director, said: "Our restrictions have caused real difficulties for some gardening businesses, so we are relieved to be in a position to take this step, which will enable them to carry on designing, landscaping, maintaining and building new features and gardens, while safeguarding their livelihoods and those of their employees.
"From today they will be able to water where necessary to get new gardens, lawns and plants established, and their clients will be able to continue this for up to 28 days."
The water company has agreed a code of practice with the Horticultural Trades Association (HTA), the Association of Professional Landscapers (APL), the Turfgrass Growers Association (TGA) and other landscape trade bodies to ensure supplies are not wasted.
It has vowed to lift restrictions for the rest of its 8.8 million customers as soon as possible.
Another six water companies are granting businesses a reprieve from the ban, Thames Water said.