Cambridge Hok representative Ross Hibbs told tomato growers that the project - which completed on 30 September, the day of the conference, was a reflection of Plant Raisers confidence in the industry and the marketplace.
Glen Little, managing director of Plant Raisers, which provides plants to growers in the UK and a handful of other European countries, agreed.
He told Grower: "I feel good about the industry and I think there are a lot of good things happening and so it's the right time to invest.
"We had about 21,500sq m of glass - we now have 28,000sq m. If you are propagating then space is a key thing. The more space you have the better quality the plants."
He added: "We have had an expansion programme over the past few years. We spent a lot of money every year on maintaining the glass we have to keep the systems up to date. We are always looking for new technology but you have to expand as well.
"We have also put in a biomass boiler and invested in new loading bays. We have spent £1m this year on improvements to the site."
Other sponsors of the BTGA event included BCP Certis, Hagelunie & Towergate Risk Solutions and CMW Horticulture.