The dissected plant in the photo has 18 fully developed leaves (V18). You can see eight ear shoots that have formed along the stalk. The plant will abandon six or seven of those shoots in favorite of one, possibly two healthy ears, most likely the upper ear shoots will be retained. The tassel, on the peak of the plant, will emerge in a few days to begin the plant’s reproductive phase of development. Photo from How A Corn Plant Develops from Iowa State Extension Service.

By Jeff Burbrink
Ag & Natural Resources Extension Educator, Purdue Extension LaGrange County

Jeff Burbrink

LAGRANGE — This time of year, corn grows like crazy. One day the corn is knee high, the next, it is over your head. The plants begin determining ear size at V5 (five visible leaf collars showing), wrapping up that process up around V12 to V15. The “V” stands for “vegetative,” or non-reproductive portion of the growth of the plant.

You may have heard stories that during this rapid growth phase, you can hear the corn grow! It is true! The process is best observed on a quiet night, just after some rain. As it grows, the plants stretch, groan, crackle and pop as they add as much as 1.5 inches of height in just a few hours. There are entire webpages and YouTubes dedicated to recording the sounds in a growing corn field.

Aside from the awesome sounds and rapid growth, the V5 to V7 stage is when the number of rows on an ear are determined. The row numbers are always in pairs of two, generally somewhere between 14-18 rows. Row numbers are mostly determined by the hybrid, and not so much by the environmental conditions like rain or temperature.

The number of seeds (ovules) per row is determined over a longer period of time, beginning about V5 to V7, and ending about V12 to V15. The first seeds begin forming near the base of the ear, and work their way towards the tip. This process is more easily disturbed by environmental conditions, like drought, floods or extreme temperatures.

About V10, the plant still has 8 to 10 viable ear shoots, consistently mostly of the leaf husk that will protect the ear, and tiny little ears best viewed under a microscope. But, not long after V10, the upper ear shoots typically take the lead, and the plant will abandon the lower ear shoots. Most hybrids eventually have one strong ear per stalk.

Most modern hybrids produce 18 to 20 leaves in the vegetative stage. The upper leaves, as you would suspect, contribute greatly to producing the tassel and filling the ear. At that point, you enter a new phase in the plant’s life cycle, the reproductive, or R stage, of development.

In the next column, I will focus on the amazing R stage, where pollen is produced, dropped onto the silks, pollination occurs, and the ear begins to fill.