Essex-based Alton Garden Centre director Andy Bunker said plants went particularly well last month - his best May in 44 years - up 35 per cent on May 2014.
Squire's garden centres in the South East were up 13 per cent - catering up seven per cent, hardy plants up 30 per cent, bedding up 15 per cent sundries up five per cent and compost up 19 per cent. Garden furniture was up 13 per cent.
Trees and shrubs at Armitage's in West Yorkshire were up 10 per cent and bedding sales were even. Year-to-date bedding sales are up six per cent, with compost five per cent up in May and year-to-date five per cent up.
Nationwide group Blue Diamond said April's plant profit was up 23 per cent and managing director Alan Roper said he did not expect that to change in May.
Showing a north-south divide, Dougal Philip, owner of New Hopetoun Gardens in Scotland, said he hoped to make budget in May.
Klondyke is looking forward to meeting pent-up demand in June after a cold spring led to flat sales against a strong 2014.
Met Office stats showed mean temperatures 0.8 degsC below the long-term average for May. Western areas and north-west Scotland had cool conditions, with some areas 2 degsC colder than normal. In contrast, eastern and south-east England have seen temperatures closer to average.