The company hopes that by adding the 50-year-old brand it will make its business less seasonal.
Mr Fothergill's intends to keep its main focus on seeds and will retain Darlac's own sales team, which will be expanded.
Joint Mr Fothergill's managing directors John Fothergill and David Carey took over the company shares held by their fathers in March. At that time Carey said: " John and I want to grow the business powerfully and profitably and have exciting plans for our future expansion."
Carey added on the purchase: "This is a significant step for our business. We remain committed to being one of Europe's largest seed houses and focussed on being the best. However, Darlac offers us wonderful opportunities to expand our portfolio in the UK and abroad."
Turnover is under £1m at present. The company will stay located at Slough as a stand-alone venture. The current staff will remain.
Former Darlac owner Peter Darban said Fothergills has a family ethos. He and his wife Maggie will offer consultancy services.
The take over of Darlac is part of a trend thats gathering pace for large garden centre and general retail garden suppliers to expand ranges, which makes the most of existing head offices, websites, catalogues, warehouses, merchandising, transport and trading relationships. This is shown by larger suppliers buying several niche companies recently.
Smart Garden took over Chapelwood last year and now have a broad range beyond its original solar products.