Climate

   This United States Department of Agriculture Plant Hardiness Zone map is probably already familiar to you, as it's found on the back of many seed packets.  It was developed by Henry Skinner in the 1930's, and divides the United States into 11 zones, with fairly similar climates, based on the average minimum winter temperatures.  It's useful for determining what vegetable plants will grow well in your area. Another aspect of climate a vegetable grower is interested in is the average date of last frost and the average date of first frost.  The growing season in your area is defined as the number of days between the last frost in the spring and the first frost in the fall.  The length of the growing season is very important as it's the amount of time that your plants have to mature and produce a crop.

   Some types of vegetables (cool-season vegetables) can tolerate cold and frost and be planted well before the average date of last frost.  A plant's "hardiness" refers to how well a plant tolerates cold.  Hardy vegetables, such as cabbage, spinach, radishes, and lettuce can be planted up to 3 weeks before the average date of last frost.  They need time to mature before it gets too hot, otherwise, they will wilt, die, or go to seed prematurely (bolt).  Very "tender" vegetables, (warm-season vegetables) must be planted after the soil has warmed up in the spring.  Some common warm-season vegetables are peppers, tomatoes, cucumbers, and melons.  These vegetables need a long hot summer to produce well.

   Use the zone map to determine which vegetables will grow well in your area and when to plant outdoors.

Heirloom Vegetable Gardening
A Master Gardener's Guide to Planting, Seed Saving, and Cultural History
by William Woys Weaver
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