The rate of corn growth between plant emergence and tassel emergence most significantly affects the total time required for maturity and establishes the date it will be ready for harvest. These stages of growth can range from 45 days to 75 days. This period is shorter for 80-day hybrid corn than 120-day hybrids. The period from silking to physiological maturity is more uniform and averages 50 to 55 days for most hybrid varieties. The silks emerge from the husks about four to eight days after tasseling. Most pollination occurs one to three days after silking. Pollen may be shed for as long as two weeks. Proper soil moisture levels and temperatures are critical at this time for pollination. Cob growth accelerates shortly after pollination.
About 10 to 15 days after silking, leaf and stalk growth stops and sugars produced by photosynthesis in the leaves move into the grain where they are converted to starches, proteins, oils, etc. Grain development is very rapid during the next 30 to 35 days. The rate declines as the plant matures. It takes 50 to 55 days for most common hybrids to reach physiological maturity after they silk. Maturity can be estimated by looking at the milk line in the kernel shortly after denting. Table 1 provides an estimated days left for maturity when daily highs are in the mid 80's and lows in the 60's oF.