The growing season is the length of time that your area has the conditions plants need to reach maturity and produce a crop. The growing season is measured in terms of the number of days between the last frost in spring and the first frost in fall. In general terms, these two dates mark the beginning and end of the time in which plants grow from seed to maturity. Some areas never have frost; instead, their dry season serves as "winter." The length of your growing season is totally dependent on your local climate.
The dates a certain area can expect to have the last spring frost and the first fall frost are called the "average date of last frost" and the "average date of first frost" respectively. These dates are used as reference points for planning and planting vegetables, but they're not infallible. The dates do, however, give you a fairly accurate guide as to which vegetables will do the best in your area. For last and first average frost dates in your area, call your county Cooperative Extension office.
The average date of last frost is not the only reference point used to determine when to plant a garden. The small maps found on the back of seed packages are hardiness zone maps, dividing the United States into areas with fairly similar climates.
The term "hardiness" is specifically used to indicate how well a plant tolerates cold. Vegetables grown in a home garden fall into one of four hardiness categories: very hardy, hardy, tender, and very tender. The date on which you can safely plant each vegetable in your garden depends on its hardiness category.
Very hardy vegetables can tolerate cold and frost and can be planted in the garden four to six weeks before the average date of last frost. Hardy vegetables can handle some cold and frost and can be planted two to three weeks before the average date of last frost. Tender vegetables don't like cold weather. They can be planted on the average date of last frost, but you will need to protect them in some way if there's a late frost. Very tender vegetables will not survive any frost and must be planted after the soil has warmed up in the spring. They can be planted two to three weeks after the average date of last frost.
Vegetables have different temperature preferences and tolerances and are usually classified as either cool-season crops or warm-season crops. Cool-season crops, such as cabbages, lettuce, and peas, must have time to mature before the weather gets too warm; otherwise, they will wilt, die, or go to seed prematurely. These vegetables can be started in warm weather only if there will be a long enough stretch of cool weather in the fall to allow the crop to mature before the first freeze. Warm-season crops, such as peppers, cucumbers, and melons, can't tolerate frost. If the weather gets too cool, their yields will be reduced or they may not grow at all.
Light is another important factor to consider when you plan your garden. Sunlight -- or some type of light -- provides the energy that plants need to turn water and carbon dioxide into the sugar they use for food. If light is limited, even a plant that looks green and healthy may never produce flowers or fruit. This can be a problem with such vegetables as tomatoes, where you want to eat the fruit. With lettuce, where you're only interested in the leaves, light is not as much an issue.
Vegetables grown for their fruit need a minimum of six to eight hours of direct light each day. Root crops, such as beets, carrots, radishes, and turnips, store up energy before they flower and do rather well in partial shade. Plants that are grown for their leaves, such as lettuce and spinach, are most tolerant of shade; in fact, where the sun is hot and bright, they may need some shade for protection.
On the next page, learn about using a cold frame and considering where light and shadows will fall on your garden.