Alfalfa harvest timing for healthier growth

By Scout Nelson

As fall approaches, North Dakota State University Extension specialists emphasize the importance of properly managing alfalfa and other perennial forage plants. James Rogers, an NDSU Extension specialist, explains that alfalfa plants begin moving sugars from their leaves to the roots as the days shorten. These sugars become stored carbohydrates, which the plant will rely on to start growing in the spring.

The plant continues to store carbohydrates until the first killing freeze, which happens at around 24 degrees Fahrenheit. However, if alfalfa is harvested or grazed after storing these reserves, it can drain them, leaving the crop without the resources needed to survive the winter.

“Gauging that last alfalfa harvest timing can be tricky,” Rogers says. He advises leaving five to six weeks before the first frost to allow the plant time to store enough carbohydrates. In North Dakota, that means the last alfalfa harvest should occur around the first week of September.

Older alfalfa plants can tolerate a later harvest, especially if they will be rotated out the following year. Younger, well-established plants can also handle later cuts but should be managed carefully. Severe winters can be tough on alfalfa, but factors like good snow cover and slow spring melts can help.

Rogers offers two management strategies for late-season alfalfa: either harvest by early September or delay until temperatures drop, ensuring minimal regrowth. For both strategies, leaving a 4-to-6-inch residual height helps protect the plant.

Late-season alfalfa can provide good-quality hay, though curing becomes harder due to cool, damp weather. If grazing, Rogers advises waiting 10 days (about 1 and a half weeks) after a killing freeze to prevent bloat risks in livestock.

“Alfalfa is a wonderful perennial forage crop that can have a long stand life in the Dakotas. Allowing alfalfa to build and preserve its carbohydrate root reserves before winter will help maintain and extend its lifespan,” Rogers says.

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