You can also increase plant survival in containers if you irrigate them before a cold period. You may also want to check your crops potassium levels by having your plant tissue analyzed. If the analysis shows that potassium levels are low, you may want to apply a potassium fertilizer. Some reports say that maintaining proper potassium levels will aid winter hardiness. Even if the crop has adequately acclimated, you may still need to protect it from cold temperatures.
Site selection is the primary factor in protecting field grown stock from winter damage.
Locate your field grown stock on sites where cold air will drain away from the planting. This means keeping them on high ground and out of low areas where cold air will settle. You may also want to provide wind breaks to prevent air movement and reduce wind burn. Seedbeds and liner nurseries are subject to frost heave. Plants under these conditions have small root systems and can be forced out of the ground as a result of the freezing and thawing of the soil.