Removes the phosphate from trehalose 6-phosphate to produce free trehalose. Trehalose accumulation in plant may improve abiotic stress tolerance. alpha,alpha-trehalose 6-phosphate + H2O = alpha,alpha-trehalose + phosphate Glycan biosynthesis; trehalose biosynthesis. Expressed in flowers. By trehalose. May be due to a competing acceptor splice site. Belongs to the trehalose phosphatase family.