Young plants grower Earley Ornamentals managing director Simon Earley said: "Summer bedding has not quite set off yet, there’s pent up demand. Garden centres have been busy even with the weather so when it gets going it will go mad."
He added: "We've had our two busiest months March and April and March was very good and was April ok.
"We've had a bit of a swing because of the euro and Brexit have helped a bit. A lot of customers are trying to support UK-based companies a bit more. That’s the impression that I get.
"We need the weather to change now. We need it to warm up, which it is looking like it's doing.
"April has been pretty good generally for our customers and now May needs the warm weather to get going."
The Met Office said overall April was warmer and drier than average, but temperatures fell as the month went on, with frosts in some areas.
Bedding grower WD Smith director Mike Smith said: "It has been a disappointing couple of weeks but [after supply fears in early April] if it had carried on as before it would have been unsustainable and we wouldn’t have had any plants left.
"We’ve caught up on everything and everything that's going out is looking fresh and is at the right size. We were still selling small plants until this week.
"It will still happen but it will just be in a shorter space of time, which makes it more difficult for us - but we’ve been there before.
"We’ve had high sales so we’re still in front where we expect to be at this point. People who get into the garden early have done it. People who wait until its sunny and come out in shorts haven't."
He said: "I'm expecting lots of people want to be out there in their garden" and "when the next wave of excitement comes with the warmer weather" but that it won't be "crazily busy" as some people have done their gardens already.
Met Office forecast for 13-22 May is for changeable weather across the UK on Saturday, with bands of rain moving north and eastwards.
Wet and windy conditions may move across the northwest into Sunday, but it will become drier in the southeast. Away from the northeast it will be rather warm, with milder nights than of late. Into next week it will be more unsettled in the northwest, with outbreaks of rain.
Further southeast it will be drier, brighter and milder, however still with the possibility of some showers that could possibly be thundery. It will be rather breezy some of the time, with stronger winds in the northwest. Temperatures will be near average in the northwest, but rather warm further southeast.
For 22 May to 5 June changeable weather with rain will be followed by more settled and drier weather at the end of the month, followed by high pressure into early June meaning warmer weather.