Corn crops way past ‘knee high at the Fourth of July’ in Central Illinois

CHAMPAIGN, Ill. (WCIA) — “Knee high by the Fourth of July,” is an old adage farmers use to measure the success of their corn’s growth. Some of the corn in Champaign County, however, is over six-feet-tall and tasseling already.

Both scientists and farmers agree the phrase is outdated.

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“I’ve heard that all my life, and a lot of farmers talk about it, but, oh my gosh, it hasn’t been that way for many years,” Champaign County farmer Dennis Riggs said.

Recent extreme heat in the area hasn’t been good for all plants, but it is causing the corn crops to thrive.

“It’s really speeding the crop up,” Dr. Fred Below, a crop science professor at the University of Illinois, said. “Corn grows by accumulating heat units. It’s 90 plus, you’re maxing the crop out at 80 units so, as long as they’re getting enough moisture it’s growing as fast as it can.”

In fact, both Riggs and Below say the 2025 corn season is near-ideal. The only thing it is missing is a little rain.

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“When it’s hot that crop goes through a lot of water,” Below said. “We could use a good rain.”

So, for now, the old adage is a myth.

Dr. Below noted — however — that the future of corn growing is engineering wind resistant crops that are shorter in stature. This means that maybe, just maybe, the crops could return to knee-high on the Fourth of July.

Just not yet.

“I think we’re going to see crops that are developed to be shorter, and that’s going to be so they’re less susceptible to wind damage,” Below said. “All things old will be new again.”

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