Vegetables divide themselves into two major groups based upon their tolerance of cold temperature and preference for cool or warm weather. It is easy to remember which group vegetables fit into based upon the part which is eaten. All leaf, stem, flower bud, and root vegetables except potatoes and sweet potatoes fit into the hardy or cool season group. All fruit vegetables except peas and fava beans are tender or warm season vegetables. Because of our cool night temperatures, most hardy cool season vegetables can be planted throughout the summer in the Pacific Northwest. Cool season vegetable seeds will sprout when soil temperature is 50 degrees or less. They will tolerate frost and a few can be overwintered. Tender warm season vegetables will not tolerate frost and grow best during warm weather. Tender warm season vegetable seeds will not germinate until soil temperature reaches 60 to 65 degrees. They grow very slowly if planted before May. However, there are some growing aids which will allow earlier planting.