The 6,000sq m building will house retail, restaurant, bakery and butchery counters as well as concessions "not always associated with garden centres". Plum Architects is the designer.
The first spade ceremony will be on 12 July at 1pm with local MP Damian Hinds.
A tower will house a camera that will relay the build not only on screens around the existing part of the centre but also online (www.countrymarket.co.uk).
Owner Gary Marshall hopes the site will reopen on the anniversary of the fire next year.