Corn height reflects a challenging spring

For generations, farmers have measured the progress of their corn crop by a simple benchmark: "knee high by the Fourth of July." For those who remember farming practices of years past, reaching that stage by Independence Day was a sign that crops were on track. However, planting timelines have changed significantly over time. Today's farmers plant earlier, and under normal conditions, corn is often waist-high — or even approaching shoulder height—by the Fourth of July. This year, corn growth across the area tells the story of a season shaped by highly variable planting conditions. While most fields have now reached at least knee-high growth, plant height varies considerably from field to field. In some areas, corn is only beginning to reach knee height, while in others it is already waist high or approaching shoulder height. Much of this variability can be traced back to the uneven planting opportunities experienced throughout the spring. The tallest corn — and soybean fields as well — are generally found on soils that were able to dry and warm more quickly, allowing growers to plant during the limited favorable conditions available in late April. This has been especially noticeable in some fields along the SR 12 and SR 613 corridors, where better-drained soils provided an early advantage. May, however, offered few extended opportunities for planting. The month began with cool temperatures and several rain events that slowed soil warming and limited field activity. As conditions improved during the second week of May, growers were able to make some progress, but planting windows remained short and scattered. A brief stretch of warmer weather in mid-May allowed for the first significant planting push, particularly in fields with better drainage. Those gains proved temporary as additional rain events returned, once again delaying fieldwork. By late May, many farmers were still struggling to find more than a few consecutive days suitable for planting. Rather than completing planting within a concentrated timeframe, growers advanced field by field whenever conditions allowed, often followed by several days of waiting for soils to dry. As a result, planting stretched over several weeks, with some acreage not being planted until late May or even early June. In some cases, farmers also chose to plant soybeans first, further delaying corn planting. As a result, corn was planted over a five- to six-week period rather than being completed in a single week. This extended planting season is why fields today range from shorter, later-planted corn to much taller, earlier-planted stands. Given adequate growing conditions, however, these differences will gradually even out over time. As the growing season advances, weather remains a primary concern. This time of year, farmers often depend on scattered thunderstorms to provide adequate rainfall. However, the start of this summer's abnormally hot temperatures have raised concerns about moisture availability later in the season — especially as corn approaches pollination. A repeat of last year's drought weighs heavily on farmers' minds, particularly because corn is more susceptible to dry conditions than soybeans. This difference can be explained by the growth habits of the two crops. Corn has a determinate growth pattern, with clearly defined vegetative and reproductive stages. Vegetative growth continues until tasseling, after which the plant produces no additional leaves or ears. By the time tassels and silks emerge, the plant has typically produced 16 to 20 leaves, and all potential ears are already formed. The number of kernels that each ear can produce is largely determined at this stage. Successful kernel development, however, depends heavily on weather conditions during the weeks surrounding pollination. Hot, dry conditions two to three weeks before and after tasseling can reduce kernel number, interfere with pollination, and cause developing kernels to abort. Severe drought stress before tasseling may limit ear size and yield potential, while stress during pollination may result in ears with few or no kernels. Even when pollination is successful, dry conditions afterward can lead to kernel loss near the tip of the ear, as the plant conserves resources for the remaining kernels. Because corn cannot start new ears after tasseling, damage during this critical period cannot be reversed. Later rains may improve grain fill, but they cannot restore lost yield potential. Corn plants do have mechanisms to cope with heat stress. Growth slows when temperatures exceed approximately 86°F, as the plant reduces photosynthesis by closing leaf openings to conserve water. Leaf rolling is another common response, helping to limit moisture loss by reducing the plant's exposure to intense sunlight. The extent of this response varies by hybrid. Soybeans, in contrast, are more resilient under dry conditions due to their indeterminate growth pattern. These plants continue to produce leaves, flowers, and pods over an extended period, typically from early July through mid-August. Unlike corn, soybeans can compensate for early stress by producing new flowers later in the season. It is common for soybean plants to abort flowers and small pods, even under normal conditions. During periods of heat or drought, this ability allows the plant to conserve resources and wait for more favorable conditions. High temperatures and limited moisture can still affect soybean development. Flowers may fail to develop into pods when temperatures exceed 90°F, and small pods may abort under prolonged stress. However, the plant's ability to continue flowering provides a significant advantage. If rainfall returns later in the season, soybeans can recover and set new pods, often as late as early August. Currently, soybeans in the area are in the flowering or early pod development stages. Hot and dry conditions may limit early pod set, but the crop still has the potential to rebound if moisture improves. This flexibility explains why soybeans generally tolerate mid-summer stress better than corn. Greater challenges exist for late-planted soybeans, particularly those planted after wheat harvest, known as double-crop soybeans. These crops depend heavily on adequate soil moisture for germination. Without sufficient rainfall, seeds may remain dormant in the soil until conditions improve. In some cases, soybean planted in late June may not emerge until mid-July, significantly shortening the growing season and increasing the risk of not reaching maturity before frost. Even when emergence occurs, continued dry conditions can severely limit yield potential. In the end, the old saying "knee high by the Fourth of July" still carries meaning, but the context has evolved. While modern planting practices often push crops beyond that benchmark, this year serves as a reminder that early-season weather still plays a critical role. Frequent rain delays in May stretched planting into several weeks, contributing to the uneven crop development seen across the landscape today. However, farmers will continue to monitor conditions closely, knowing that the weeks ahead will be critical. Timely rains and moderate temperatures will determine the outcome of this year's crop. Until then, hope for good weather remains at the forefront of every farmer's mind. Ed Lentz is agriculture and natural resources educator with Ohio State University Extension — Hancock County.