Willowbrook Garden Centre, between Taunton and Wellington, was under around 25cm of water at the height of 21 November's flash floods.
A representative told Horticulture Week: "We have flooded again and are closed. I don't know how long for but it was six weeks last time though it won't be as long this time because we have lots of decorating still going on.
"We reopened two weeks ago last Saturday and now it's happened again. The water went straight through the shop, eight and a half inches deep."