RHS Chelsea Flower Show grower exhibitors say their displays are likely to suffer after "unprecedented" cold weather leading up to the 22-26 May event brought plant growth to a halt.
Pheasant Acre Plants owner Rob Evans, who won gold last year for his gladioli, said: "Things growing well came to a dead stop in the past couple of weeks. In some of our later shows we will have fewer varieties of gladioli available to us.
"The May and June shows such as Chelsea and Hampton Court are the ones that will suffer because gladioli normally catch up by July. They're not getting the heat and light they like. I thought they were going to be early but we've had two or three weeks of colder weather and very little sunlight on them."
Devine Nurseries owner Tony Devine said of the alliums and Eremurus he has been growing outdoors in East Yorkshire: "We've only got a few weeks until Chelsea and we're starting to panic a bit. Our plants have just stopped growing. We could do with some warm weather to get things going again.
"There will be some varieties we can't take if that does not happen and it's not like we can do anything else. We were watering outside in January because it was so dry and we're only half a mile off the sea. To use water outside in January is unbelievable. But the past fortnight, things have gone the other way."
Chris Beardshaw, who has designed the Furzey show garden at Chelsea, said: "We were trying to hold our azaleas and rhododendrons back and now we're trying to encourage them forward because of the weather.
"We don't want the buds sitting because they could rot. Digitalis is a nightmare because cool and wet does it no good and neither do high temperatures.
He added: "Grey hairs will be the order of the day at Chelsea this year, and designers using fleet of foot when it comes to replacements. But we have a wealth of plants we can still grow."
Show stalwarts on the challenge of changeable weather
Bob Sweet, shows development director, RHS
"We get lulled into a false sense of security when the sun comes out and plants put a spurt on, and before we know where we are there's frost on the ground and it's very difficult to deal with."
Mike Clare, Potash Nurseries
"It's difficult growing weather. One minute you're opening the vents and the next it's a hailstorm. The plants don't know what to do."