This video from My Forage System explains the winning conditions for preparing alfalfa for winter.
The survival of alfalfa in winter is influenced by several factors, including:
Hardening: This period begins in autumn with the decrease in light and temperatures. There are three stages of hardening:
Stage 1: Development of cold tolerance between 2 and 5 degrees Celsius.
Stage 2: Maximum tolerance and dehydration.
Stage 3: Prolonged freezes and dehydration.
Soil moisture: Alfalfa needs to dehydrate to get through the winter. Excess water in autumn and November can have a negative impact on plant survival.
Snow: A snow cover of at least 10 centimeters protects the roots and crowns of alfalfa from freezing.
Temperature: The first day which is minus -15 degrees Celsius and the last day which is minus -15 degrees Celsius are critical for alfalfa.
Diseases: Insects and diseases can reduce alfalfa's sugar stores and make it more vulnerable to frost.
Variety: There is a great deal of variability between alfalfa cultivars in terms of their winter hardiness.
The video also features tips for increasing alfalfa's winter survival, such as:
Sowing first year: First year seedlings are more resistant to cold stress than seedlings from later years.
Accumulate 600 degree days during the winter period: This allows alfalfa to store enough sugars to survive the winter.
Maintain snow cover: Snow protects alfalfa roots and crowns from freezing.
Control insects and diseases: This allows alfalfa to maintain its sugar reserves.