They can also survive a light freeze of 29 F to 32 F, although with some damage. Hardy Plants Hardy annuals can survive a moderate freeze with some damage. Their seeds will tolerate severe freezes, and can be sown in the fall. If planting in the spring, you can sow their seeds as soon as you can work the soil. The root systems of hardy perennials go dormant during the winter, sending up new shoots in the spring.
All hardy perennials can survive frost.
However, the severity of the cold they can survive varies, which is why they are assigned a zone or hardiness rating. Click here to find the Hardiness Rating for your area. This USDA rating does not take into account the hottest temperatures a plant can tolerate. Western gardeners must also consider the degree of heat and drought their plants can survive. An excellent resource for the western gardener is Sunset's Climate Zone Map .