I'm here to walk you through staging a corn plant
and what's going on inside!
Obviously the first thing we look for is GERMINATION, and the first sign of that is the radicle or first root breaking through that seed coat. EMERGENCE is the next step, when the straw-like structure called the coleoptile breaks through the soil and the leaves come up through it.
More leaves get pushed upwards through the rolled-up center called the whorl, resulting in V1, or vegetative 1, which means the corn plant has one fully-opened “collared” leaf.
We count the number of leaves from the first rounded leaf to stage, and V2 comes next! During this time, and for the next few weeks, everything above ground is actually just leaves!
The stem of a V3 corn plant is still safely underground and the yield component we’re determining up to this point is plants per acre!
V5 is a special stage, because this is the point when the stem starts to grow, making the plant more vulnerable to damage. Around V6, the ears per plant is starting to be determined.
Fun fact - when the corn stem starts to grow and comes above ground (~V5), everything the plant needs (including all leaves, the tassel, and ears) are present. They just need to grow and develop!
Usually before V7, we see tillers popping up in corn. At this stage, we’re continuing to set ears per plant.
V9 is, again, nine collared leaves. When plants reach this stage, summer heat typically causes the plants to really take off, because growing degree days are accumulating quickly!
When we reach V10, staging becomes difficult because lower leaves are likely no longer attached to the stalk. To stage plants in the field, slicing them crosswise and counting nodes is usually the best option to stage correctly.
V12 is a significant stage because we have a new yield component that the plant is working on – ear size. In this case, we’re specifically looking at kernel rows per ear.
Fun fact - there are almost always an EVEN number of kernel rows on an ear of corn. This is because floral "ridges" develop into two pistillate flowers, which become kernels. You can find paired rows by checking kernel alignment on an ear!
The last of the V-stages roll around, and this is a point when we can really pinpoint when pollination will occur. By opening up the whorl, we can count the number of leaves left to unfurl and multiply that by the typical number of days per leaf (usually around 2 by this time) to give a good estimate. At V16, we're adding a new component of ear size - kernels per ear row.
Corn usually has around 20 leaves. The tassel will emerge from the last curled leaf and expand its branches, which we would then describe as VT. This is the end of the V-stages and we go to the R or “Reproductive” stages, which take up the last half of the corn plant’s lifetime.
R1 is the "silking" stage, and it begins when we have silks popping out of the ears. The kernels at this point are negligible and the ears are small. Tassels should be dropping pollen by now.
Fun fact - the difference between the time tassels start shedding and silks appear is known as the ASI, or anthesis silking-interval, which is a really important number for good pollination! Most tassels drop pollen for a period of 3-5 days, depending on weather conditions.
R2 is the “blister” stage, and this is identified by kernels with some small, clear, liquid inside and drying silks (turning brown).
R3 is the “milk” stage – my preferred stage for eating corn-on-the-cob, because the kernels are tender, yellow and filled with a white “milky” liquid.
R4 is the “dough” stage, because the kernel filling becomes more starchy and dough-like.
Fun fact - at R4, the grain still only has about 1/3 of its total dry weight. We aren't done yet and there's a lot more filling to do!
R5 is rightly called the “dent” stage because dents appear on the tops of the kernels as the water percentage of the kernels begins to drop. R5 lasts for several weeks, and the progress can be tracked with the “milk line” which is visible on the kernel profile. R5 is broken into percentages based on the location of this milk line, which slowly progresses towards the center of the cob.
The final stage, R6, is physiological maturity, in which a “black layer” is visible. This layer is found at the base of the kernel where it was attached to the cob, called the pedicel or tip-cap, and is basically the equivalent of the corn kernel’s belly button.
Any weight change after this point is a loss of moisture, which is needed to prepare the grain for harvest and storage. Kernel moisture is approximately 30% at maturity and 18% is the general target for harvest, unless high moisture corn is desired.
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