The six stores are the former NWF garden centres bought by Notcutts in October 2008 for £14.5m.
Notcutts IT director James Moon said: "We wanted to migrate these stores onto the same technology we are currently using in our other 13 stores, to have all stores running on the same platform. Having worked with K3 for a number of years, they were the natural choice to provide their POS and back office solution."
Moon added: "K3 knows the business and most importantly understands our needs. We wanted a one-stop shop and K3 was able to provide us with the technology we required."
K3 Retail sales director John Little said: "We are delighted to be supporting Notcutts on this project."
He added: "K3 Retail has a successful history of implementations in the garden centre sector and we are very pleased to continue to work with such a thriving business as Notcutts."