DIY Network

Planting Times Paul James offers information on determining the best time to plant. From "DIY Gardening & Landscaping" episode DIG-124

Paul James, host of HGTV's Gardening by the Yard, offers information on determining the best time to plant.

Proper planting dates are determined not by the calendar but by current weather conditions. Conventional wisdom says that both trees and shrubs may be planted whenever the ground can be worked, which in many parts of the country is year-round. But if your climate has severe winters, it's best to plant trees and shrubs during the spring or a few weeks after the snow melts and temperatures are likely to remain above freezing. If you live where winters are mild or summers are hot and dry, fall planting may be your best bet.

The best way to determine the ideal planting time for trees and shrubs in your area is to consult your local nursery or home-and-garden center, your agricultural extension agent or an experienced gardener.

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	Figure A
	Figure B
	An inexpensive soil thermometer can help you determine the proper time to plant seeds.

Spring-flowering bulbs such as tulips and daffodils must be planted in the fall, no matter where you live (figure A). In Zones 2 and 3, that means September; in Zones 4 and 5, October; in Zones 6 and 7, November; and in Zone 8, December. In climates warmer than Zone 8 you'll likely have to chill spring-flowering bulbs in the refrigerator if you expect them to bloom, or force them in pots.

Certain perennials, including wildflowers, may be planted in fall in many parts of the country, but virtually all may be planted in spring. Plant perennials in the spring when there is no longer any danger of frost. Likewise, nearly all annuals, especially those that native to the tropics, should be planted in spring, when daytime temperatures are consistently in the 70s. Nurseries often begin receiving stocks of annuals before the preferred planting date, but don't assume that because they're available it's time to put them in the ground.

Turf grasses come in both cool- and warm-season varieties. If grown from seed, cool-season grasses such as fescue and rye should be planted in early spring, from March to May, or during September and October. Warm-season grasses such as Bermuda and zoysia germinate best when temperatures are in the 70s and 80s--between May and July in most parts of the country. If you plan to lay sod (figure B) rather than seed a new lawn, observe the same planting dates. Check with local sources for the best times to lay sod, and get a guarantee if you can.

If you look at a planting guide for vegetables, you'll see that spring vegetables should be planted in late winter, summer vegetables in early spring, and fall vegetables in mid- to late summer. Adding to the confusion are the terms "cool-season" and "warm-season" vegetables, which refer not to planting time but rather to the type of growing conditions they find optimum.

When you're planting vegetables from seed, soil temperature is the most accurate indication of when to plant, especially if you're the sort of gardener who likes to get a head start on things. Local weather forecasters often include soil temperatures in their weather reports. Or buy an inexpensive soil thermometer and take the readings yourself at a depth of 4". Once soil temperatures are consistently in the 50s you may safely plant most spring vegetable seeds. A few weeks later, when soil temperatures are in the upper 60s and 70s, you can plant summer crops.

Before setting out transplants of various vegetables, know whether each is a cool- or warm-season variety. Cool-season vegetables--including most salad greens, peas, onions and cold crops such as cabbage, cauliflower and broccoli--can tolerate temperatures slightly below freezing. Warm-season vegetables such as tomatoes, peppers, eggplant, squash and melons may die if air temperatures drop below 50 unless you've protected the transplants with cloches or some other plant-protection device.

Check with local sources for specific information on planting dates. Don't rely exclusively on calendar dates: local climates may vary considerably from one year to the next.

Another way to determine safe planting dates is to watch for certain fairly reliable clues from nature. For example, you can safely plant corn once oak leaves are the size of a squirrel's ear. Potatoes can go in the ground about the time forsythia blooms, and practically anything can be planted about the time kids start playing in the sprinkler. No matter how carefully you plan, however, somewhere along the way you'll lose a crop or two because of a late-spring or early-fall freeze.