July 2024 Corn Growth

BY Dairyland Seed Agronomy Team

As we think about celebrating our country’s 248^th birthday on July 4^th, 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 (corn) 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. This would 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 V6th to V7th growth stage. If we are fortunate enough to receive good weather with adequate moisture and temperatures and, barring any catastrophic weather event, almost all corn planted in April and May 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-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 (GDU’s) needed to put on a new leaf or growth stage is narrowing down closer to 50 to 60 GDU’s versus the 80-90 GDU’s 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 2–3-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 2-3 week +/- time frame.