Garden retailers need to be watchful of changes to sale regulations, said Trading Standards Institute lead officer on prices Martin Fisher.
He said new Government guidelines, which he helped draw up in May, meant that old, misleading sale law head been superseded.
Full prices only had to be available for 28 days before going down to sale prices.
That "misled consumers", said Fisher. Now regulations say higher prices should have been charged "more often than lower prices".
Fisher, a Cornwall Trading Standards officer, said garden centres were less likely to offer misleading prices than retailers such as carpet, furniture and clothing sellers, whose "sale price is often the normal price".
Many garden centres are set to cut prices in January sales.
Klondyke chairman Bob Gault said: "We'll have a genuine half-price sale after Christmas."