The administrator is RSM Tenon Recovery.
Alexander Mackie's Don Earnshaw said: "We've had a tremendous amount of interest."
Owner Debie Gordon blamed Somerset County Council's closure of the B3081, between Waterside Road and Shadwell Lane, in August 2009 to make repairs to a collapsed river wall at Shadwell Bridge.
Her second business, Pet Barn, based within the garden centre, is also for sale.
She said: "I can't believe one little thing can ruin it for everybody else and that highways at the council can get away with it. We had a petition with signatures from customers who complained about the difficulty finding us.
"There is nothing I can do about it now. The money we now earn goes straight into the administrators' bank. I hope someone takes over with as much passion as we had and makes it work."
RSM Tenon Recovery joint administrator Tim Dolder said: "We have a lot of experience in financially distressed garden centres. The plan is to maintain the garden centre as a going concern as long as it is commercially viable to do so. Specialist agents have been instructed to market the business. Additionally, the existing staff have been retained, including the owners."
A Somerset County Council representative said: "The county council deeply regrets Wincanton Garden Centre going into liquidation. The economy is going through difficult times and the county council does everything it can to support local businesses and to keep traffic moving, but occasionally road closures are necessary.
"The scheme at Shadwell Bridge was a major reconstruction and it was essential to close the road for public and worker safety. The works were actually praised locally for their efficient delivery. During the scheme the council worked hard to respond positively and helpfully to all the queries that emerged about the road closure before and during the work."
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