Frost‑risk gardening alert

Gardeners in western Massachusetts are being told to cover tender plants and hold off on new warm-season planting as overnight temperatures dip back toward freezing. (westernmassnews.com) Western Mass News published the warning on April 21 after speaking with local garden-center managers, who said newly planted flowers, vegetables, and other soft transplants are the most exposed in a late cold snap. UMass Extension also flagged a possible frost for Sunday night in its April 14 Vegetable Notes newsletter. (westernmassnews.com) (umass.edu) A frost and a freeze are not the same thing. Iowa State University Extension says frost can form when plant surfaces hit freezing even if air temperatures are slightly above 32 degrees, while a freeze is more damaging because the air and plant tissue itself drop below 32 degrees. (yardandgarden.extension.iastate.edu) That difference matters in April because many western Massachusetts gardeners have already started setting out tomatoes, peppers, basil, annual flowers, and greenhouse-grown starts after a stretch of warm weather. Iowa State says action is usually needed once overnight lows slip into the mid-30s, especially for vegetables, annuals, and tropical plants grown outdoors. (yardandgarden.extension.iastate.edu) The calendar still argues for caution across much of the region. The Old Farmer’s Almanac lists the average last spring frost at May 6 in Greenfield, May 9 in Springfield, and May 13 in Pittsfield, using 1991-2020 National Oceanic and Atmospheric Administration climate normals and a 30% frost-probability threshold. (almanac.com 1) (almanac.com 2) (almanac.com 3) The National Weather Service office in Boston and Norton showed no active watches, warnings, or advisories on the afternoon of April 21, but gardeners do not need a formal advisory to see plant damage. Iowa State notes that frost advisories are generally issued for forecast lows of 33 to 36 degrees, and sensitive plants can still be hit before a warning threshold is met. (weather.gov) (yardandgarden.extension.iastate.edu) The usual short-term fix is simple: cover plants before sunset with fabric that reaches the ground, then remove it after temperatures rise the next day. Iowa State recommends bringing containers indoors when possible and says cold frames or hoop tunnels can also protect spring plantings. (yardandgarden.extension.iastate.edu) Not every plant needs rescue. Iowa State says woody shrubs, roses, small trees, and many established perennials usually tolerate temperatures at or just below freezing better than tender annuals and vegetable starts, which is why garden centers are telling customers to protect transplants first. (yardandgarden.extension.iastate.edu)