You do not say in what area of the country you wish to plant your garden. Generally, in areas that have four seasons of warm and cold weather, hardy vegetables such as peas, parsnips, and leafy vegetables such as kale and spinach can be planted in the early spring and will also grow late into the fall season when frost would kill the tender plants. When growing the tender vegetables such as squash, tomatoes, cucumbers, etc., you should wait until chance of frost is past, around the middle of May. Of course, temperatures vary widely across the country, so you should consult your local garden center or county extension service to find out the best times for your particular area.