Corn Plant Growth

As we think about celebration of our county’s 247^th birthday on July 4, it brings to mind the phrase “corn needs to be knee high by the fourth of July to have a successful crop.” Or other adaptations of this are “corn knee high the fourth of July, makes the cribs crack in October and November.” The average knee height of an adult male in the United States is 22 inches, and the average knee height of an adult female being 20.29 inches puts put the average knee height for an individual in the United States at 21.145 inches.

In correlating this back to corn and using the total plant height, it would put that plant at about the V6 to V7 growth stage. If we are fortunate enough to receive good weather with adequate moisture and temperatures, and barring any catastrophic weather events, almost all corn should be knee high by the fourth of July, if not sooner.

Most corn planted from mid-April to mid-May across the Dairyland Seed footprint is in the V8 (collar on eighth leaf) to V12 (collar on twelfth leaf) growth stage or more. By the time the corn plant has reached the V8 to V12 growth stage, it is already starting to influence the total potential length of the ear/cob. Also at this growth stage, the amount of Growing Degree Units (GDUs) needed to put on a new leaf or growth stage is narrowing down closer to 50 to 60 GDUs versus the 80-90 GDUs needed at V1-V2.

If we average 64°F in the evening and 81°F during the day, we would be accumulating 22.5 GDU/day, which would allow us to put on a new growth stage in a 2-to-3-day frame. If this holds true, and depending upon which growth stage the corn plants are at now, and if our weather pattern stays favorable, we could start to see corn silks and tassels start to emerge in a two to three +/- week time frame.