The Duchy bought Close Farm last year and is tendering for horticultural consultants to bid to develop the garden centre. Presentations are due this week.
The garden centre will not be in the grounds of Highgrove, the private residence of the prince and Duchess of Cornwall, but just under a kilometre away towards Tetbury.
Tracy Wilson, who used to grow for the Duchy Estate, said: "The existing nursery, Close Farm, was bought last year by the Duchy, and they want to give it a facelift.
"They are looking at doing a whole raft of things like catering and adding extra facilities. Knowing the prince, I suspect there will be an educational element."
Wilson worked for the prince for 27 years. She ran his only retail nursery, in Lostwithiel, Cornwall, before becoming a partner at Pengelly Plant Centre in St Austell last May. She said organic themes were likely to feature strongly at the garden centre, which would tie in with the emphasis of the Highgrove shop in Tetbury. "It has the potential to be a great garden centre as there are few around in those parts. I wish them every success: it's a brilliant spot to have a centre."
A representative for the prince said: "There are plans for the nursery but we are not ready to publicise them. There's a crucial meeting later this month, after which more concrete plans can be talked about."