Should this year’s asparagus fern be cut in the fall?

When is the perfect time to chop asparagus fern once the growing season is finished? The answer is “it all depends.”

 Asparagus FernVarietal dormancy differences. Photo Credit: Dan Brainard, MSU.

Many asparagus fields in Michigan have begun the dormancy process, turning from the chlorophyll-green color that typifies photosynthesizing plants to a bright, vivid yellow. The loss of green pigment signifies that these plants are no longer photosynthesizing, but does not indicate full dormancy. That state has only been reached when the fern turns the same light brown color that one sees on dormant pasture or mature cornfields. Asparagus fern can be mowed or chopped any time after the “dormant brown” color is seen without losing any of the energy that will go into making next year’s spear crop.

Some varieties of asparagus seem to reach this state earlier than others. Canadian hybrids like Millennium or Tiessen are bred to have a quick and complete dormancy response, going from green to yellow to brown in a matter of a few weeks, often allowing growers time to chop fern before winter snows set in. New Jersey hybrids, such as Jersey Supreme and Jersey Giant, have a much slower dormancy response and are often still mostly yellow or even green when heavy snow makes field activities impossible.

Even if fern reaches full dormancy before winter weather makes chopping or mowing impossible, there are two schools of thought on whether the fall is the correct time to do this necessary chore. Many growers prefer to leave dead fern standing as a way to trap additional snow that might otherwise blow off the field. Standing fern may well catch and hold snow equivalent to an additional inch of rain. That water should be available to the dormant asparagus crown when growth starts in the spring. However, other asparagus farmers, especially the larger growers or growers of other spring planted crops, are often pressed for time when weather clears in the spring. Getting the chore of mowing dead fern out of the way in the fall frees up time for other spring tasks like spreading fertilizer or applying pre-emergence herbicides. These growers count on normal spring rains to provide adequate moisture for growth.

Ultimately, the choice to chop or mow old asparagus fern in the fall or spring comes down to the preference of the grower.

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