Embryonic ear shoot development takes place early in the life of the corn plant, usually by about the V5 to V6 growth stage.
The number of kernel rows on the corn ear is also determined early, by about the V8 growth stage. The number of kernel rows determines the "girth" of the corn ear. Each row of kernels starts out as a single row that splits into pairs. This is why there are always an even number of rows of kernels on the ear.
The number of corn kernels per kernel row is believed to be determined by the V15 growth stage or perhaps as early as V12. The number of kernels per row determines the ear length.
From emergence to the V10 growth stage corn adds a new leaf collar about every 82 growing degree days (GDDs). Growth speeds up after the V10 growth stage, with a new leaf collar being added about every 50 GDDs. A typical corn plant will produce about 18 to 20 leaves.
The tip of the emerging corn tassel may be noted as early as about the V13 growth stage, to as late as the V17 growth stage.
Silks emerge from kernels at the base of the ear first (tip of the ear last). Kernels at the tip of the ear are least likely to be fertilized if the plant is under stress. Kernels at the tip may abort following fertilization if the plant becomes stressed during grain fill.
Pollen grain germination occurs within minutes after a pollen grain lands on a receptive silk. A pollen tube, containing the male genetic material, develops and grows inside the silk and fertilizes the ovary within 24 hours. Pollen grains can land and germinate anywhere along the length of an exposed silk. Under hot, dry conditions, the silks dry rapidly and may not contain enough moisture to support pollen grain germination or pollen tube growth.
Pollen shed is not a continuous process. The release of pollen will stop when the tassel is either too wet or too dry and starts again when moisture and temperature conditions are favorable. Peak pollen shed usually occurs between 9:00 and 11:00 a.m. Pollen is not likely to be washed off of silks during a rain. Pollen that is shed prior to a rain usually attaches itself to the silks so quickly that it is not likely to be washed off.
Silks will take 2 to 7 days to emerge. With adequate moisture, the silks will grow 1 to 1 ½ inches each day and continue to grow until fertilized. The ability of the silk to receive pollen generally exists up to 10 days after silk emergence. After 10 days, the ability of the silk to receive pollen decreases rapidly. Silk elongation continues until pollination is successful, although elongation eventually ceases as unfertilized silks senesce.
The tassel is usually fully emerged and open before any pollen is shed. The length of pollen shed varies, but is usually 5 to 8 days with the peak production coming about the third day. The first silks will emerge about 3 days after pollen shed begins.
Silking is delayed more than tasseling when the corn plant is under moisture stress. Under extreme drought conditions, the silks grow slowly and may not emerge from the husks before the pollen is shed. Emergence of silks after pollen has been shed is commonly referred to as "missing the nick" and results in poor to complete lack of kernel set.
Check pollination in the field. Each potential kernel has a corresponding silk. About 2 days after pollination, the silk will detach from the developing kernel. Carefully remove the husks and gently shake the developing ear. Silks that remain attached indicate those embryos have not been pollinated.
Contact your FS Crop Specialist for your agronomic information.
Image 1: 7 days of silk growth with no pollination
Image 2: Ear shoots visible in split corn stalk, about V10