Staging Corn Development
Although all corn follows the same general pattern of development, the time between growth stages and total leaf numbers varies between corn products, planting dates, locations, and years.
Early-maturing corn may develop fewer leaves or progress through different stages faster than later-maturing products. Corn development is also directly related to temperature. The length of time between growth stages will differ as temperature varies within a growing season and specific year.
Germination to V3
By now, your 2009 corn is well past germination. But let’s review what occurred.
Immediately after planting, metabolic reactions in the seed begin. With adequate moisture and soil temperatures of 50°F or warmer, the radicle emerges. Germination can happen as quickly as 2 to 3 days after planting—or after 65-80 growing degree units (GDUs) have accumulated.
A day or so later, the coleoptile emerges. With favorable conditions, the lateral seminal roots emerge about 3 to 4 days after the radicle. These early roots function for about 6 weeks, providing the young corn plant with nutrients and water. During this period, the nodal root system is also developing. It will eventually become the main supplier of water and nutrients, later in development.
The coleoptile normally ruptures when it is exposed to sunlight at the soil surface. If it ruptures below ground, the seedling has a hard time pushing upwards. It may turn yellow, twist, or ‘leaf out’ below ground. Reasons for this occurring may be cloddy soil, herbicide injury, crusting, or extremely cold soils. Corn typically emerges after an accumulation of 100-120 GDUs, about 6-10 days after planting. Cool and dry conditions will slow emergence.
V3-V6
Corn at the V3 stage starts to experience development changes. Root hairs are growing from the nodal roots and seminal root system growth has virtually ceased. At this stage, the plant should not be adversely affected by mild hail, wind, or frost, because the growing point remains below ground. However, surface flooding can kill corn in only a few days. All leaves and ear shoots that the plant will eventually produce are now being formed.
Near the V5 stage, leaf and ear shoot initiation will be complete and a microscopic tassel will form in the stem apex tip. The stem apex at tassel initiation is just under or at the soil surface, although total above-ground plant height is about 8 inches.
The V6 growth stage arrives approximately 3 weeks after emergence. The growing point comes above the soil surface. The root system is well established and nutrient uptake is rapid. Injury at this point can have a significant impact on yield.
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