Alfalfa and grass must be confused. March started out fairly warm and dry. Alfalfa, which very much develops according to heat, took off. Then April was cold and quite wet and things quit growing. May has been dryer but still cold with a few warmer days. Growth has been by stops and starts.
When will first cutting be ready? It depends. The variability from year to year on maturity for alfalfa can be considerable. Maturity depends on Growing Degree Days, micro-climate (elevation, closeness to lake), soil drainage, what grass is planted with it and to a lesser extent variety. Calendar date at 40 NDF can sometimes vary by two weeks between years and micro-climates.
Grasses don’t tend to fluctuate from the calendar date from year to year quite as much as alfalfa. However, maturity will depend on all of the above and also fall cutting management and fertilization. Grass cut late last fall will be later maturing than fields last cut in September. Fields with nitrogen applied in early April will likely mature quicker. Of course, orchard grass will be ahead of most fescues, Reed Canarygrass and Timothy.
When to mow is obviously a complex question with many variables. But don’t wait for your governor to tell you when to mow. It will be best for you and your crop advisor to monitor fields and consult the following table from Dr. Jerry Cherney of Cornell. From my experience, it is the best place to start in determining your window to mow.
Use this table by evaluating the height of the tallest alfalfa in different areas of the field and the percentage of grass in the stand.
Table – Estimated NDF of a mixed alfalfa-grass stand based on alfalfa height and the percent grass in the stand. Target NDF for each mixture is highlighted. Using the table below, a field with 40% grass and 60% alfalfa will be ready to mow when the tallest alfalfa stems in the field are 26” tall. For straight grass fields, look at the stage of maturity on the grass (boot stage is ideal) and the height of the tallest alfalfa in the area.