The old-timers always said if you plant late when the soil is warm, corn will jump up more quickly, and grow faster. That is true to a point, but it doesn't mean it will yield more. In fact, there is sound data that it will yield less. However, if you've planted corn within the past two weeks or still have wet spots to plant, here's a glimpse of what you can expect.
It will typically require about 125 growing degree days for corn to emerge, according to the Purdue University Corn & Soybean Field Guide. If it is warmer when you plant, more GDD's accumulate per day. So, yes, corn should emerge faster.
The next area to watch is leaf stage development. From emergence until stage V10, or the 10th leaf collar, it takes an average of 82 GDD units for each collar that develops. This is based on the system where the minimum GDD that promotes growth is 50 degrees, and the maximum temperature is 86 degrees F. Temperatures above 86 do not add to the growth of corn, and at some point, may become detrimental. High nighttime temperatures, as evidenced a year ago, can also be detrimental.
Leaf development actually speeds up after the V10 stage. It's estimated that it takes about 50 GDD units to produce each leaf from V10 to the final leaf production of the plant. Remember that these leaves are the reproductive factory of the plant that turns light into sugar.
What happens in a year when corn is planted later than normal is that the same hybrid that would need 2200 GDD units to reach maturity if planted May 1 can usually reach it in about 2,000 units. It's good from the standpoint of having mature corn before frost, but is not good from the standpoint of reaching maximum yield potential fro that hybrid. That's why unless you have the same hybrid side-by-side planted at different dates, it's difficult to determine what the hybrid might have yielded if planted earlier, even if the yield for a late planting date seems high, such as 200 bushels per acre.
Since the time required or the plant to develop is shortened, leaves will probably appear slightly faster, and the plant will grow taller and be less girthy. However, researchers who documented that corn plants speed up their maturity process if planted late note that the largest part of the increase occurs later in the season, once the plants have developed ears and are striving to get kernels to the black layer stage. That's reasonable if you remember that a plant's goal is to produce as many viable seeds as possible. Dave Nanda, now with Seed Consultants, Inc. like sot say that the plant's number one job is not to make a farmer money, but to produce as many viable babies as possible. Everyone wins when the plant can achieve both goals at the same time.