Summer squash are essentially immature squash fruits picked when they are tender and the seeds non-existent. Any winter squash variety can be picked and eaten at this early stage (best a few days to 1 week after the fruit starts to form), but certain varieties have been bred to produce lots of fruits as well as have especially tender and delicious flesh. Zucchini are summer squash varieties that have a long cylindrical shape – other summer squash shapes include crookneck and pattypan.