The cool temperatures have dampened market demand making it hard for growers to clear spring stock, and meant more fuel than normal is needed to heat glasshouses for keeping plants alive.
NFU horticulture board member and British Protected Ornamentals Association chairman Ian Riggs said: "Unlike food crops that tend to dominate the headlines, the £1.8 billion British ornamentals sector often gets overlooked. This is shaping up to be another poor year for plant growers, which after a bleak 2012 season could have catastrophic consequences.
"There have already been some high profile casualties, with many more growers cutting back on production to reduce wastage and cost. But that doesn’t help those who are now receiving cancellations for bedding plants that have already been grown to order.
"With consumers not showing much interest in getting out into their gardens during the cold weather retailers are abandoning the spring season and moving their attentions to summer stock. This leaves growers holding vast quantities of unsold stock, which will most likely have to be thrown away as there is no other market."
Earlier this year the NFU announced that it would be holding a supply chain summit to bring together ornamental growers and buyers to try and find ways of sharing risk and reward more equitably throughout the supply chain.