Cool-season crops are those that germinate and grow at lower temperatures of spring and fall and are not injured by light frost. Experienced gardeners begin the vegetable growing season on St. Patrick’s Day (March 17), weather permitting, with the planting of peas, spinach, and onion sets. Garden calendars provide guides for the best planting dates for vegetables.

Cool-season crops generally perform poorly during periods of extended hot temperatures. Leaf lettuce and other greens BOLT and produce flowers and the foliage tastes bitter. Peas stop producing pods.

Other crops, such as onions and potatoes, require cool weather to become established before producing the harvest during the summer months. Insulating techniques, like cold frames, hot beds, ROW COVERS, and cloches, are often used to further extend the harvest of cool-season vegetables.

Warm-season crops do not grow well at temperatures below 50ºF and are killed by frost. Seeds of these vegetables will often rot if planted in cold, damp soil. Not only is their growth retarded by cool weather, but also fruit set will be delayed.

Cool-season crops Crops not injured by light frost are asparagus, broad bean, broccoli, brussels sprouts, cabbage, collard, garlic, horseradish, kale, kohlrabi, leek, onion, pea, radish, rhubarb, shallot, spinach, turnip.

Crops injured by frost but intolerant of temperatures above 70ºF are beet, carrot, cauliflower, celery, chard, Chinese cabbage, endive, lettuce, mustard, parsnip, potato, Swiss chard.

Warm-season crops Crops for planting after danger of frost is past are cantaloupe, cucumber, eggplant, lima bean, New Zealand spinach, pepper, pumpkin, snap bean, squash, sweet corn, sweet potato, tomato, and watermelon.