Cranberry Spring and Fall Frost Tolerances (from a table developed by C. J. DeMoranville, UMass Cranberry Station, 1997):
|Spring Cranberry Frost Tolerances|
|Appearance of the bud||Early Black & Howes varieties||Ben Lear & Stevens varieties|
|Spring dormant (bud reddish)||18° F||20° F|
|White bud stage (loss of dormant color in bud)||20° F||22° F|
|Slight loosening of bud scales (no bud swell)||22° F||25° F|
|Bud swell (cabbage head or popcorn stage); 2mm bud||25° F*||27° F|
|Bud elongation (Bud is growing out/up)||27° F**||29.5-30° F|
|Roughneck (more than 1/2″ new growth) through hook stage||29.5-30° F||29.5-30° F|
* = After 5-7 days, increase tolerance to 27° F even if there is no change in appearance.
** = After 5-7 days, increase tolerance to 29.5°-30° F even if there is no change in appearance.
|Fall Cranberry Frost Tolerances|
|Maturity Level||Early Black||Howes||Stevens||Ben Lear|
|Deep blush on exposed surface||27° F||27° F||27° F||27° F|
|Deep blush||26° F||26° F||26° F||26° F|
|Red||25° F||25° F||25° F||25° F|
|Deep red||23° F||23° F||23° F||24° F|
|Maroon (1-2 weeks later)||23° F||20° F||22° F||24° F|
|Over-ripe (end of October)||23° F||23° F **||23° F **||24° F|
** = loss of tolerance when over-ripe
Please note that each variety will reach a given stage on a different date. Generally, Early Black and Ben Lear will both color early and Howes and Stevens will color later. This tolerance chart is based on color development, which is used as a visual guide to ripening, a chemical and physiological process. In some years, lower tolerances were found. However, we cannot predict when this will occur so conservative figures are presented here. In each of three years, cranberries showed tolerances at least as low as these for the stages listed.