The other temperature related item of great importance to growing plants is the growing season, the number of days between the last frost in the spring and the first frost in the fall. I have found that “the books” are very misleading and that local gardeners or you local county agent is a much better source of information on this. The growing season is especially important when growing vegetables and annuals since they only have one growing season to strut their stuff and must produce their blooms or fruit within that frost free time. If you live in zones 2 or 3 you may have to start some plants indoors in order to get them to produce the flowers or fruits you wish as they need more frost free days to grow to maturity than the area provides. Check the back of you seed packages and you will usually see a statement that you will have fruit in some specified number of days. This information will tell you if you need to consider starting seed indoors or buying nursery grown stock.
Frost Free Days
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