The new 6,000sqm building will also house Christmas products from this autumn.
The first floor mezzanine restaurant in phase one will also open in September.
Redfields which is on a 35-year lease became the twelfth garden centre in the Blue Diamond Group on the 2nd June 2010.
Redfields was founded in 1977 by father and son team Roy and Richard Jones. Shortly after the initial opening, they were joined by Roy’s daughter Ann and son in-law Malcolm Goater.