It's time to determine whether the winter wheat came through the winter well enough to keep the stand. The best way to do this is to do a stand count. To do a stand count, use one of the following two methods:
1) Count the number of plants in a foot of row at several locations in the field. Take an average and convert in plants per acre using Table 1.
2) Take a hula-hoop, let it fall, and count the number of plants inside the hoop. Repeat this at random several times across the field and calculate an average. Use Table 2 to convert the count to an approximate population per square foot or acre.
Table 1. Average number of plants per foot of row for different row spacing and plant densities per acre.
Table 2. Adjustment factors to multiply the number of plants inside a hoop and convert the number in to number of plants per acre.
If your winter wheat hasn't started greening up again, you may be wondering if your winter wheat crop survived. To evaluate whether your winter wheat survived, I suggest you do the following: dig up several seedlings across the field and cut them longitudinal (lengthwise) with a very sharp knife or a safety razor blade. If the crowns look white/yellow to light green, they are healthy and will continue to grow. If you find that the crown has turned tan to brown and soft, it did not survive the cold weather.
In addition, you can check whether seedlings will grow by trimming the roots and leaves down to about ¼ to ½ " above and below the crown. Place these seedlings on a wet paper towel and place the towel in a Ziploc bag or plastic container that can be sealed. Place the container at room temperature and check for re-growth in 24-48 hours. Viable seedlings will show re-growth almost immediately (Photo 1). It will take longer than usual, but as long as the crown is healthy, a stand will establish and your field of winter wheat may not need to be destroyed.
Photo 1 Regrowth of young winter wheat seedlings after 36 hours incubation in a Ziploc bag at room temperature (photo courtesy of Blake Vandervorst)
If stands across the fields average 15-17 plants/ ft2 or more you can leave the stand and expect near maximum grain yields. Often winterkill is not evenly distributed across a field but rather patchy. Smaller patches with stands as low as 8 plant / ft2 are probably worth saving. Weed control will be more troublesome with thin stands and the crop's growth will be variable making management decisions such as the correct timing of a fungicide application more difficult. If the patches with complete winter kill are larger than a couple if square feet and cover more than 20% of an area, such as in a ditch or on a knoll you may still want to consider replanting that area of the field to something else.