Cool Season vs. Warm Season Vegetables

Know your last frost date in the spring, and the first frost date in the fall for your area.

Denver Metro: Average last frost date May 15
Denver Metro: Average first frost date October 12

Cool-Season Vegetables

Cool-season crops are the first ones to plant in the garden year. This can be anytime from several weeks to a couple of months before the last frost date. These early vegetables cannot only withstand cold temperatures, they need them to germinate, grow, set fruit and mature.

It is important to plant cool-season crops early enough in the spring so they can complete their full cycle up to harvest before the temperatures get too warm. While some cool-season vegetables can withstand hot weather and will still grow, their quality becomes inferior.

Many spring cool-season crops can be sown again in the fall. Keep in mind the average first frost date and days to maturity.

Cool-season vegetables are generally grown directly from seed in the garden, either as soon as the soil can be worked in the spring, or until the soil and air have reached certain minimum temperatures that are usually indicated on the seed package.

Common cool-season vegetables: asparagus, beets, broccoli, Brussels sprouts, chives, cabbage, carrots, cauliflower, Swiss chard, kale, leek, lettuce, onion, parsnips, peas, radishes, spinach, and turnips.

Warm-Season Vegetables

Warm-season crops require higher soil and air temperatures; they are always planted after the last frost date. The long season crops are usually started from seed indoors and transplanted into the garden as soon as the soil and air are warm enough. Tomatoes, peppers and eggplant are good examples. Fast growers like beans, corn, squash can be directly sown outdoors in the garden.

Common warm-season vegetables: beans, corn, cucumbers, eggplant, melons, peppers, zucchini and summer squash, pumpkin and winter squash, sweet potato, tomato, watermelon.