The purpose built facility increases the company's laminar flow cabinet capacity by 30 per cent and has more than doubled the growing room area.
It is now selling 750,000 plants a year and it hopes to increase production further.
Managing director Dr Neal Wright said: "The future looks good. We are certainly helped by the Euro and the demand for young plants is increasing. We have just taken over a big contract from Holland on orders for 2012-13."
The company used to export 30 per cent of its plants but after years of a strong pound that figure had fallen to almost zero.
As the euro has strengthened, the company's exports have recovered to around 15 per cent of total sales. Wright said he was confident it could climb further. "We are hoping it will go up again to 30 per cent at least. Forward orders are good so our projections are up 10 per cent for next year," he added.
About 50 per cent of stock is propagated to contract, up from 20 per cent five years ago.
Wright attributed the growth in forward orders to the company's determination to work with growers and he said he hoped that they could do even more in future.
Work on the new building began 12 months ago but the company has been considering the expansion plan for more than three years.
"We weren't sure whether it was the right time to do it but sales are up about 20 per cent on what we were expecting," said Wright.
"Now we have the capacity to do more and we expect to be working to capacity. The business coming in over the past 12 months has been a lot better than we expected."