Poblem is, at least here in the U.S., is that most pumpkins are hybrids... that is they are bred by intemixing two or more sub-species of pumpkins. This is done to achieve a desired "style" of pumpkin. The use of the resulting hybridized seeds often either won't grow or they revert to one of the sub-species used and produce a fruit nothing like you intended... best to buy a new packet in the spring or, better yet, any good garden supply store will have "started" plantings that give you a head start on the season. In most cases, be sure to plant at least two or more to assure pollinization... Good luck!