Timing Last Cutting for Alfalfa
By Tanner Marquardt, University of Minnesota Extension
PRESTON, Minn. (08/07/2023) — As we head towards the end of Summer we need to be thinking about the timing of last alfalfa cutting. When it comes to your last cutting of alfalfa, you’ll need to ensure that you make it early enough that the plant can regrow to a height of at least six inches. This regrowth helps to ensure that the plants can survive the winter. The recommended last cutting should not be after the first week of September. Having at least six inches of stubble helps improve the survivability rate by catching snow to help insulate the soil. Suppose you cut your alfalfa later than that, until roughly October 15th. In that case, you risk the survival of your alfalfa during the winter. During the fall, alfalfa stores energy to survive the winter, and when harvested later in the fall, the plant must use that energy to regrow instead of storing it for winter.
In some cases a late 4th or perhaps 5th cutting is needed to ensure you have enough feed to get through the winter. In this case you should aim your harvest between October 15th and early November. Cutting around this time minimizes the regrowth time of your alfalfa, therefore not wasting its winter stores. If this is done, leave a few extra inches of alfalfa standing to protect the crowns and help keep the soil insulated.
Besides the proper amount of growth before the frost there is also another thing that can affect how well your alfalfa stand survives the winter. Breaking dormancy early can result in severe injury. This can be caused by soil temperatures reaching more than 40 degrees followed by extreme colds. Snow acts as an insulator that can protect against extremely low temperatures as well as fluctuating temperatures, four to ten inches of snow can greatly affect the survivability of your alfalfa.
If you have questions about this or any other agriculture, horticulture or natural resources topic please reach out to the Fillmore or Houston County Extension office at 507-765-3896 or 507-725-5807.