The consideration to cut alfalfa later into September or October has implications for next spring.
Typically alfalfa needs six weeks of uninterrupted growth before the average first frost to winterize. The winterization process itself, takes three weeks, but having a total of six weeks helps to mitigate risks by allowing the alfalfa to move stored reserves to the roots and become acclimated to changing temperatures. The added three weeks before winterization acts as insurance for early frosts as well.
Allowing alfalfa to successfully winterize is key to having productive stands next spring and reducing long term losses in your alfalfa stand.
Stress during the season also plays a role in the winterization process. Environmental stresses such as drought, heat, hail or frost cause slower regrowth and shorter stands in season. Even the amount of times we cut stands and the age of the stand are stress considerations.
If you are trying to push the six-week rule, remember that alfalfa that has been heavily stressed throughout the season or older stands would benefit from having uninterrupted growth to complete the winterization process.
When planning your last cutting for older or stressed alfalfa stands, keep in the mind the dates for establishing fall alfalfa as a guide to your last cutting. The window for growth leading into fall ranges throughout the state of Nebraska.
In northern and western portions of Nebraska the last cutting has wrapped up and stands are beginning the winterization process. However, as we move south the date is expanded to mid-September. In areas that have also received adequate rainfall it may be tempting to try to take another cutting in September or even push October.
Remember that these fields will have a slow start next year and may have issues overwintering if the stands are stressed or older.
Bottom line: alfalfa needs at least six weeks of uninterrupted growth into the fall to be the most successful when it comes to winterization. Edging into that six weeks is an added risk. Later cuttings can be possible for stands that are newer and have been under relatively low stress this season, but expect delays next spring.