The present management will stay on after Hillview entered a "strategic alliance with the Garden Store and Burford House Garden Store, with an intention of acquiring the business".
Douglas-Davies said two sites were freehold and four leasehold.
He added: "They all have good horticultural foundations. There's an opportunity to develop strengths and add to them."
He said he was looking forward to working with the Garden Store team over the next few years. Gilbert Evans advised Garden Store, which is owned by Marcus Eyles and Neil Stevens.
Garden Store sites are at Billing, Charlecote, Tamworth, Wolverhampton, High Wycombe and Tenbury Wells.