The time for planting kitchen garden crops depends upon where you live. The number of days between the last frost in spring and the first frost in autumn is the length of your growing season. Every crop you plant, must germinate, grow and come to harvest during your growing season. If your growing season is too short for the crops you want to grow, you must assist Nature by extending the growing season with crop coverings or protectors.

Cool-season vegetables are best suited for the beginning and end of the growing season, for planting in spring, autumn, and winter. These plants grow best as the soil and air temperatures become warmer in spring and as the heat wanes in late summer and autumn. Cool-season vegetables thrive when the temperature highs are in the range of 70º to 75ºF (21-24ºC). (Cool-season crops usually require a minimum germination temperature of 40º to 50ºF.)

Hardy cool-season vegetables are the best selection for planting in the early spring garden. They can be sown directly in the garden as early as 2 or 3 weeks before the last frost in spring. The seeds of hardy cool-season vegetables germinate best in cool weather and their seedlings can withstand a light frost without injury.

Half-hardy cool-season crops can be sown in the garden on or around the average date of the last frost in spring. At about the time of the average last frost in spring, the ground is warming and the weather becomes more settled. The seeds and seedlings of half-hardy crops require temperatures warmer than freezing.

Planting the autumn and winter kitchen garden may require a bit more planning than planting the spring garden. Crops for autumn and winter harvest that are not grown under cover must be planted early enough that they come to harvest before the first freeze in autumn, but not so early that the heat of summer reduces their output. In spring, the garden is nearly a blank slate with plenty of room for planting. In late summer and early fall when the autumn and winter garden is planted, room may be limited--many late harvest summer plants are still in place.

Crops for autumn and winter harvest require enough heat to grow and reach maturity, but not so much that they are scorched or grow too fast, set seed, and wither too soon. Cool-season crops are the best choice for planting in late summer and early fall, just as they are suited for growing in spring.

A cool-season crop planted in autumn can take as much as three weeks longer to come to harvest as the same crop planted in spring. That's because the days are growing shorter and less warm as autumn turns to winter.