What to Plant & When to Plant It
The number of days between the last spring frost and the first fall frost is considered the growing season. These dates are important when determining what to plant when. Seed packets also give guidance on planting times.
Cool-season crops, such as peas, lettuces, spinach, greens, and radishes, thrive in cool temperatures and can be planted in mid- to late spring, before the last frost date and again in late summer and early fall for a second harvest. Warm-season crops, such as tomatoes, peppers, eggplant, and squash, are planted after the last frost date. If planted too early, they will be killed or damaged by late frosts or freezes. Also, if seeds or transplants are planted too early, they will just sit in the soil, waiting for it to warm up before they grow.
How Cold Is It? Definitions
Light freeze—29 to 32 degrees F (1.67 to 0 degrees C). Tender plants will likely be killed or severely damaged.
Moderate freeze—25 to 28 degrees F (3.89 to 2.2 degrees C). The tops of most plants will be heavily damaged.
Severe freeze—Colder than 24 degrees F (4.4 degrees C). Most plants will be killed or damaged.
Lettuces, peas, seed potatoes (pieces of untreated potatoes, each with an "eye"), onions, carrots, radishes, and beets can be sown directly outdoors a few weeks before the last frost or immediately after. For instance, carrot and radish seeds can be sown outdoors 4 to 6 weeks before the last frost and lettuces about two weeks after.
Cabbage, broccoli, and Brussels sprouts transplants can be planted outdoors around the last spring frost date. These cold tolerant plants also can be grown in late summer and fall for an extended harvest.
Many crops can be started from seed indoors, and many can be sown directly in the garden outdoors. Seed packets offer the best guidance regarding the timing of starting seeds indoors or out. Usually, warm-season crops are started indoors about 6 to 8 weeks before the last frost date.
Two plants that are best started indoors are tomatoes and peppers. Other warm-season crops can be sown directly outdoors.
Warm-season crops are very cold sensitive and will not develop roots or grow until the soil temperature reaches a certain minimum degree. If seedlings are planted outdoors too soon, they may rot or be killed by cold temperatures.