Plots on Main Avenue next to the Grand Pavilion suffered most as water run-off from the marquee emptied into their gardens. Several needed pumps to get the water down to a manageable level.
At the Cloudy Bay garden designed by Andrew Wilson and Gavin McWilliam the water coming from the roof of the pavilion flooded plants out of their beds.
"It’s a shame, there was a lot of work done and suddenly it was washed away," Wilson said. "The build up to Chelsea is often difficult for weather."
At the Laurent Perrier Garden, designed by Luciano Giubbilei, the Crocus team had to dash to protect delicate flowers. "Site foreman Mark Whyman said: "We had a hail storm yesterday which wasn’t the nicest. We had to stand under a sheet of fleece for half an hour to protect the Lupins. We had a laugh about it but the rain seemed to go on and on."
It is one of several gardens which is using camping gazebos to protect plants from both rain and sun.
The Landscape Associates at The RBC Waterscape Garden designed by Hugo Bugg also suffered from the pavilion water chute effect while Paul Cowell of PC Landscapes said the RHS had to borrow its pump.
Landscape Associates site foreman Richard Pease said his team had two days less time than other gardens because construction of the Grand Pavilion meant they could not get onto their plot.
Other exhibitors griped that they had not been given the wifi access code for the site.
"We got absolutely hammered on Tuesday said David Dodd of The Outdoor Room which is building Adam Frost’s Homebase Garden. "Every time it rains it’s like being set back a day."
Speaking on Wednesday M&G Investments designer Cleve West said: "The rainy days slowed everything up but days like this have really made a difference."
The show site was a flurry of activity on Wednesday as a warm sunny day allowed landscapers and garden designers to press ahead with planting.
The show’s youngest garden designers The Rich brothers, of Rich Landscapes, whose Bord na Mona garden is one of the most advanced, were not fazed by the rain though.
"Being from Wales you get used to it, it’s all going fairly well and we’re really enjoying it, " said Harry Rich.
"We’ve pleased the plants have come and look great. We have a great team, we couldn’t have wished for it to have gone any better. "