"Plant early and you'll plant often" is an old saying containing more than a kernel of caution. Timing is everything in gardening. Start too soon and you'll lose your crop to lingering spring frosts. Too late and you'll gamble with winterkill before you can harvest.

So when is the right time to put plants in the ground? That depends on your location; soil type and temperature; microclimates, and plant selection, said Shawn Olsen, an agriculture professor with Utah State University.

"One of the most underutilized tools in gardening is the soil thermometer," Olsen said. "Plant your cool weather crops when the soil warms to 35 or 40 degrees. Go with your warm weather crops when it gets up to 55 or 60 degrees."

Also pay attention to the variability of maturity dates listed on seed packets and plants, he said. "Many radishes, for example, mature in 30 days."

Microclimates play a large role, Olsen said.

Anything that is heat-absorbing or gives off infrared radiation at night is useful. That means planting alongside a house, stone walls or outbuildings. "Generally speaking, the south side of a building is warmer; the north side cooler," Olsen said.

Loose, sandy soil with a sunny exposure will dry early, he said, while "wet, packed soil takes longer. Your plants will just sit there."

Have some season-extending tools available: cold frames, frost blankets, grow lights, high or low tunnels, row covers or a hobby greenhouse, said Lewis Jett, an extension horticulturist with West Virginia University.

Raised beds or anything that warms the soil, like mulch, is going to be helpful, he said.

It also pays to know your USDA plant hardiness zone.

Learn to distinguish between cool-season and warm-season plants.

Cabbage, broccoli, onions, peas, radishes, spinach and turnips are typical cool-season crops. These hardy plants will tolerate light frosts, prefer temperatures in the 50- to 60-degree range and lose some of their quality in the heat. They can be planted again in mid- to late summer for a fall harvest.

Tomatoes, cantaloupe, watermelon, eggplant and pumpkins, on the other hand, are tender plants craving warmth, or readings at least 15 degrees higher than the cool season varieties.