By Blake Jackson
During spring, alfalfa often breaks dormancy and begins active growth, only to encounter a return of freezing temperatures. According to Dwane Miller, Extension Educator at Penn State Extension, alfalfa is naturally tolerant of cold conditions and can handle short periods of sub-freezing weather without significant harm.
Temperatures between 25°F and 30°F may cause slight deformation in young, developing leaves, while older leaves typically remain unaffected.
For more serious damage to occur, nighttime temperatures must drop to 24°F or lower for at least four hours, which can freeze the plant’s growing point, or meristem. Brief exposure to temperatures near freezing, including light snowfall, usually does not result in injury.
To evaluate potential damage, growers should wait two to four days after a cold event before inspecting their fields. Signs of injury include wilted or blackened leaves, particularly at the top of the plant where exposure is greatest. If no visible symptoms are present, the crop has likely escaped damage.
When injury is minimal, such as slight burning along leaf edges or damage to only a few leaves, yield loss is negligible, and normal harvest timing can be maintained. If the plant’s bud remains intact, continued growth is expected.
However, if the top portion of the stem, including the bud, is killed, that stem will stop growing. In such cases, new shoots may develop from leaf nodes or crown buds, though overall yield may decline.
If frost-damaged plants are too short, it is best to wait for regrowth before harvesting. Conversely, if damaged stems have reached around 20 inches or more, harvesting is recommended, as the forage remains safe and nutritious.
Following harvest, maintaining proper soil fertility and allowing adequate regrowth will support stand recovery.
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Categories: Pennsylvania, Crops, Alfalfa