Environment Agency spokesman George Leigh said: "Below average rainfall could increase the likelihood of drought management measures in some areas."
Hayloft Plants' Derek Jarman said: "There is a worry about the lack of water after the dry winter. The biggest problem of a hosepipe ban is consumers would not be allowed to water, so they don't buy plants."
Rainfall across the Thames catchment was 77.4% of the 131 year historic monthly average, with 40.5 mm from 1 - 31 March. December rainfall was 75% below normal and October was 61% below normal.
Reservoir storage on the 31 March 2017 for London as a whole was 95% (Thames Valley 98% & Lee Valley 83%) and Farmoor storage was 96%.
Southern Water said its Bewl reservoir was 78% full, 10% below avergae for the time of year.
Britain has experienced parched weather in the six-month period between October and March - the driest since 1995 and 1996, according to the Met Office.
But South East Water's head of water resources Lee Dance said that while the winter has been drier than usual, the company does not envisage water shortages this summer.