Quantil director Alastair Hill said: "I don't think the market will drop off dramatically but growth is going to come from people reaching their full potential - some people are not ordering what they could sell.
"I'd be surprised if there was another year of growth. The market is going to stay where it is for a while. We've had three or four years of huge upward trend and it has got to peak at some point. I don't see where market growth is going to come from now, though I'd welcomely admit it if I'm wrong. We've had huge secondary support from the media."
Of Quantil's 100-plus varieties supplied to the Garden Centre Group, Dobbies, 300-400 independents and one of the big sheds, runner beans are top sellers. Hill said new and unusual varieties will only have a tiny part of the market.
He added: "A lot of new people who have come in are going to have had failures but in 2010 we grew by 30-40 per cent but some through expanding customer base." In February, Hill predicted 20 per cent growth. Quantil grew 1.5 million strips in 2009, with 80 per cent to independent garden centres.
Ball Colegrave won the most innovative display award for its vegetable exhibit incorporating Vertigrow units. Marketing manager Stuart Lowen said Ball Colegrave had seen 30 per cent growth in 2010 in vegetable seeds and plugs and expected growth to continue.
"Interest in veg is continuing to expand and our new veg catalogue has doubled in size for 2011. We're still in the growth part of the curve because there is so much media coverage. It is going to continue though perhaps not at the level of the past few years but it's not at a point where it is going to plateau."
Lowen said patio vegetables such as peppers and tomatoes were doing best alongside strawberries.
Garden centre consultant Eve Tigwell said: "There is still growth left because a big chunk of the industry has not noticed it has happened. " She said "a lot of centres don't do as much as they could".
She added that most stop in June but could be selling grow-your-own container potatoes for Christmas as well as other vegetables. "Garden centres should extend the grow your own season - not all year round but pretty close." Seed companies had veg seed rises of five to 10 per cent in 2010 and expect similar gains in 2011.