The most significant difference between the two groups is that winter squash has a hard shell and stores well for long periods and summer squash has soft skin, which does not store and is perishable. Both are of the genus Cucurbita. Summer squash are all the species pepo and winter squash includes several species: maxima, argyrosperma, moschata and also some pepo. For example, zucchini is a common summer squash and pumpkin is a winter squash.