Assessing Freeze Injury to Alfalfa
While several areas of the state experienced lows below 28°F this week, widespread alfalfa losses are not expected at this time.
If you're concerned about whether your alfalfa may have suffered frost injury, remember that frozen alfalfa usually needs some time to recover before damage can be estimated.
To assess the extent of the damage, don’t just look for frozen or wilting leaves. You need to
determine if the growing point was killed. This growing point, also called the apical meristem, is where all new leaves, stems, and branches initially develop on alfalfa. It is located inside the dense cluster of unfolded leaves at the top of the main stem.
Because it is inside a cluster of leaves, the growing point is somewhat protected from cold
injury. Exposed leaves and stems all around it can be frozen, wilted, and dying while the growing point cluster survives, waiting for warm weather before continuing to grow. If the growing points in your alfalfa survived the freeze, just wait for growth to begin again.
If the growing point was killed, however, growth will cease on that stem. Any new growth must come from new crown shoots or from lower branches. While the existing plant remains intact, regrowth often is delayed. But you don’t have to harvest this damaged growth; plants will begin to grow again on their own although it might take a little longer.
Cutting damaged plants often hastens development of regrowth from good, healthy fields; howevr it also adds extra stress to plants. If you do cut damaged plants, wait until plants get a little more mature before you take your next cutting. I suggest cutting now only if there is enough growth to justify the time and expense of harvest.
Check your alfalfa plants to truly see if the tops and growing point are dead or if recovery has begun. Then decide whether to harvest or just wait for growth to renew naturally.