Dry beans are very sensitive to frost and should be planted after risk of frost has passed. The ideal germination temperature for dry beans is 15°C or higher. Cool soil temperatures at planting may delay germination and reduce rates of emergence, particularly if seed is of poor quality.
Frost damage may be apparent as dark, water-soaked spots on wilted leaves or plants. General stunting may be observed if low temperatures persist. In a frost tolerance study, white and pinto bean seedlings were less tolerant to frost than soybean and field pea. At -3.25 to -3.50° C in a growth chamber, 50% of pinto and white bean seedlings died.
The extent of early-season frost damage will depend upon where the plants were damaged. If the plant is damaged below the cotyledons, it will not recover. If the growing point is damaged, but the lower stem remains intact, the plant will send out new shoots from the base of the leaves or cotyledons. Wait a few days before replanting to see if these shoots appear.
When replanting, it is best to terminate the existing crop first. Planting into the damaged crop will result in fields with highly variable maturity. This causes challenges with timing of pre-harvest herbicide application, timing of harvest, and green material at harvest.
References:
D.W. Meyer and M. Badaruddin. 2001. Frost tolerance of ten seedling legume species at four growth stages. Crop Science 41 (6). DOI: 10.2135/cropsci2001.1838
Robert Hall (editor). 1994. Compendium of Bean Diseases. US Department of Agriculture.
Agronomy Guide for Field Crops – Publication 811. Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA).