I have gotten several calls over the last week or so asking about corn growth stages, specifically how to count leaves. Most years this is fairly simple to determine leaf stages from V1 to V5. However this year many early planted fields have had some light frost damage and the lower leaves will likely disappear quicker than normal, making growth staging a little more difficult. Figure 1. Shows corn plants that are at the V2 stage (2 collars) but with four leaves visible. The leaf must be fully expanded with the collar visible to count the leaf. The 3rd leaf, although clearly visible, is not fully expanded does not have a collar and is not counted yet.
Figure 2. is from corn I have this year at Marianna, which has had a tough 6 weeks. Leaf 1 and 2 had frost damage and will quickly disappear making growth staging more difficult. This V4 plant has 7 leaves visible, but only 4 collars, thus it is a V4 plant. It took about 3.5 weeks to get to the V4 stage from emergence. This plant will likely be at the V5 stage next week.
Please contact me by email at firstname.lastname@example.org, or by phone at 501-749-6207 if you have questions or comments regarding this information.