There are loads, depending on what you are looking for,
there are the big diy shops with garden centres inside them, torres novas and ourem.
there are several great garden centres around Tomar for plants, trees. some at
at Ferraira D. Z. or north of Tomar 6k, on the 110 or Asseiceira has a great big one, or agri loja just out of Town on the sao pedro rd.