Digitalseed: Plant Hardiness Definitions

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Plant Hardiness Definitions

Hardy. Not injured by light frosts and seed will germinate at rather low temperature. May be planted about two weeks to a month before the average date of the last killing frost in the spring. In general, these plants can safely be planted as soon as the soil can be worked into condition. Includes: onion sets, smooth peas, cabbage plants (well-hardened), kale, kohlrabi, brussel sprouts, spinach, turnip, radish, asparagus, and rhubarb.

Half-Hardy. May be planted about the time of the last killing frost. The seeds of this group will germinate at rather low temperatures, but the young plants are injured by frost. Includes: lettuce, beet, carrot, chard, parsley, parsnip, heading broccoli, early potatoes, onion seeds, garden peas, celery plants, and cauliflower plants.

Tender. Injured by the light frost and does not thrive at low temperatures even though frost does not occur. These should not be planted until all danger of frost is past. Includes: snap bean, tomato, sweet corn, and sweet potato.

Very Tender. Does not thrive until the soil has become warm and the seed will rot in the ground unless the soil is warm. Includes: eggplant, pepper, cucumber, watermelon, muskmelon, lima bean, squash, and pumpkin.

(Ref: UCCE San Diego publication CP-275)

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