Gretton started working for Ted Meredith in 1979 and in recent years programmed and oversaw the production and growing at multiple nursery sites of in excess of 270 cropping programmes annually with over 8,000 individual varieties.
Evesham-based Gretton said: "I've always worked in a family firms and there's still a lot in horticulture out there with that sort of family ethic."
He added that changes he has seen in the industry is how it is increasingly difficult to make a profit as supermarkets, multiples squeeze the suppliers, who tend not to have the automation to cut costs, particularly when they are producing high numbers of lines.
He added: "If you specialise you can be more efficient but then you're at the mercy of your customer, so you try to broaden the range you grow, but you can't easily mechanise hundreds of different varieties and containers."
The company acquired Coblands in Kent in 2006, RA Meredith & Son Nurseries in Fretherne, Gloucestershire, in July 2013 and Mahood Brothers in Lathom, Lancashire, in November 2014. It employs more than 250 people overall. The nurseries produce 18 million plants per annum including bedding, herbs, vegetables, trees, shrubs, perennials and herbaceous products for the amenity and retail market.