Advancements in Spring Frost Protection to Sustain Cranberry Production in Massachusetts

American cranberry (Vaccinium macrocarpon Ait.) is a perennial woody plant that produces buds on short vertical branches known as uprights. These buds must overwinter to acquire adequate winter hardening for protection against frost damage in the spring. Once buds have broken dormancy, the plant requires protection from cold temperatures and desiccating winds. In this study, we evaluated three thermal time models, or growing degree day (GDD) models, as decision tools for initiating spring frost protection, and two methods for applying irrigation for spring frost protection (conventional vs. cycling). We found that the WI(30-5) thermal time model provided the most accurate estimates of the phenology of buds in both normal and abnormal spring temperature years. Although irrigation cycling resulted in slightly higher bud damage, it did not reduce fruit yield. This finding is consistent with bud damage localized in one to two floral initials, with the remaining two to four initials producing flowers and berries comparable to beds with conventional irrigation. In addition to not differences in fruit yield, water savings of up to 35% were obtained in cycled frost irrigation compared with conventional frost irrigation.