No matter whether you planted early or battled the weather and just planted recently, getting corn to V6 was likely a struggle. The first hurdle is emergence; then comes the “ugly duckling phase” where corn looks as gangly as a newborn calf. Sooner or later, permanent roots take over, weather conditions improve, temperatures rise, and corn reaches V6. A rapid growth phase follows, signaling the race to the finish is on.
“Important things happen around V6,” says Matt Montgomery, an agronomist and education lead for Beck’s. “The growing point is above the ground, and plants are making decisions based on their environmental surroundings. Around V7 or so, the rapid growth phase takes over, and you can literally watch corn grow overnight.”
Many fields in the western Corn Belt were planted early and are well into or even past the grand growth phase already, with tasseling not far off. Yet the Corn Commentary field in south-central Indiana was planted May 19. Due to cool, wet weather, plants didn’t spike through for nearly two weeks. With warmer weather recently, the field will approach V6 and the rapid growth phase soon.
Why V6 stage matters in corn
A premier resource about corn development, “Corn Growth and Development,” was published by Iowa State University in 2011. Mark Licht, current cropping systems specialist at ISU, notes that it underscores important developments stage by stage during the life of the corn plant.
Technically, V6 is defined as the stage when corn plants possess six leaves with full collars, Licht says. Several important things occur at V6. Here is a closer look:
All leaves are present. Every leaf the plant will ever have will form by V6, although some are too small to see without a magnifying glass, Licht says.
Lower leaves diminish. The first leaves that emerged wither and begin to tear away as the stalk expands. This makes determining actual leaf count more difficult.
Internode elongation begins. It is minor at this point, with most of this process occurring after V6 as the rapid growth phase unfurls.
Growing point transitions. Once enough internode elongation occurs, the growing point rises above the soil surface.
Primary ear shoot develops. Find it only with magnification at this point at nodes 12, 13 or 14, Licht says. Ear shoots are also present at other nodes, forming at lower nodes first.
Ready to determine row number. This usually occurs at V7, shortly after the primary ear is initiated. Because initial ear rows divide laterally, two by two, row number is always even.
Kernel initiation begins as florets. This process starts next, beginning at the base of the ear and continuing over time. Kernel initiation continues until one week before silks emerge, Licht explains.
Tassel develops. Initiation of the tassel starts around V6, although you can’t see it with the naked eye. By V7, you can find it if you dissect a plant, Licht says.
Crop update:
Get scouting shoes ready as season unfolds
This year may seem like a long season already if you were able to plant early. For others, it may seem like it is just getting going. The wide range in planting dates means corn will be at various stages throughout the season.
Here are recent observations across the Midwest. As noted, tar spot has already made an appearance in multiple locations. Agronomists and plant pathologists urge keeping an eye on it.
Indiana: Tale of two seasons. Farmers were sidedressing nitrogen in northern and north-central counties the first week of June. South of Interstate 70 in central Indiana, some farmers were finally able to plant corn. As a result, crop size and stage of growth varies across the state.
Because Indiana is a long, narrow state, planting often begins in the south first. Some fields in southwest Indiana could be planted early, and those cornfields are off and running. For the most part, though, drier weather north and wetter weather in south-central and southern counties flipped the script this year.
Ohio: Planting date and GDDs. Weather also flipped the script across much of Ohio. A few fields were squeezed in early. Osler Ortez, Taylor Dill and Laura Lindsey are in the third year of a multi-state project comparing planting dates for corn and soybeans. Data on growing degree day accumulation based on various actual planting dates in their 2025 trials paint an interesting picture.
For example, the first three planting dates in Clark County at the Ohio State University ag station were April 18, May 12 and May 27. Accumulated GDDs from planting to June 15 were 790, 531 and 355, respectively. In northwest Ohio in Wood County, planting dates so far were March 27, April 16-17, May 12 and May 29. GDDs were 748, 700, 482 and 304, respectively.
So, corn planted April 16 in Wood County, Ohio, has nearly a 400 GDD unit jump on corn planted there on May 29. That explains the big variation in growth stage occurring so far in Ohio, Indiana southern Illinois and other locations where wet weather was a major factor.
Iowa: Tar spot. Alison Robertson, Extension field crops pathologist at Iowa State University, notes that tar spot was reported in Poweshiek County on June 13. She also notes that it was no surprise. In previous years, tar spot was first observed on June 30 in 2022, June 23 in 2023 and June 7 in 2024 in central Iowa.
“The [disease] triangle rules,” Robertson says. “Every county in Iowa has a history of tar spot, and consequently, the pathogen is present. Every county in Iowa grows corn, and consequently, the host is present.
“What really matters, however, when it comes to tar spot, is the weather, especially temperature. Mean daily temperatures of 64 to 73 degrees F for 30 days, and relative humidity of less than 90% for two to three weeks, favor the disease.”
Meanwhile, temperatures greater than 73 degrees and extended periods of humidity greater than 90% are not favorable for tar spot development, she explains. In Iowa, the mean daily temperatures in July and August are 76 to 78 degrees, which considerably slows development of the disease.
In fact, as of June 15, the Crop Risk Tool, formerly Tarspotter, useful in predicting when conditions could be right for tar spot, indicated conditions should be less favorable as temperatures climbed higher. Roberton reiterates that if you are using fungicides to manage tar spot, the best timing for applications is VT through R3 growth stages.
Kansas: Tar spot too. In case you’re keeping score, the first sighting of tar spot in the U.S. in 2025 was in Doniphan County, in the northeastern corner of Kansas, on June 11. Yes, that is early, but the first report in 2024 was in that county on May 27.
“Now is the time to intensify scouting efforts,” says Rodrigo Onofre, writing in the June 12 edition of Agronomy eUpdates, distributed by Kansas State University. “If you wait until there is significant disease pressure in the upper canopy, a fungicide application may be too late. The early disease onset we’re observing this year raises concerns about yield loss. Generally, early observations of tar spot have corresponded with high yield loss.”
Fields scouted in mid-June in Kansas were between V3 and V10, which increases risk for disease spread and development. Recent rains likely helped to promote tar spot development. However, Onofre isn’t recommending immediate fungicide applications.
“A well-timed, informed fungicide application will be important to reduce disease severity when needed, and we recommend holding off until the disease is active in your field and corn is at least V10 growth stage,” he writes. “Scouting will be especially important if wet weather continues. There are several fungicides that are highly effective at controlling tar spot when applied from tassel, or VT, to R2, or the milk stage. I would recommend picking a product with multiple modes of action.”