Brace roots from the sixth leaf node are developing and the permanent roots have continued to elongate and proliferate, eventually reaching a depth of about 5 to 8 feet and spreading several feet in all directions. In some hybrids, brace roots will also develop from the eighth and ninth leaf nodes or even higher. Some corn plants in North Dakota may only develop 16 leaves. Eight weeks after the plant emerges, it is entering the late vegetative stages if the plant has not already developed its total number of plant leaves. During this time, plant stress can greatly affect yield.
Moisture stress two weeks before or after silking can cause a large grain yield reduction .
The four-week period around silking is the most effective time for irrigation if water supply is short. Tips of upper ear shoots may be visible at the top of leaf sheaths by V17 in hybrids which develop more than 16 leaves. The tip of the tassel may also be visible by V17 in more prolific-leaf hybrids. V18 and other numbered vegetative stages which may follow. The vegetative plant is reaching full size in prolific-leaf hybrids .