Let's focus on the seedling stage of the corn plant. If we know growth stages, we can plan field operations better.
Most hybrids have 18 to 22 leaves based on relative maturity. How do we measure stages of maturity?
The collar method is most common. Count the number of leaves with collars which develop when the leaf partially unclasps the stem. A leaf collar is the light-colored band at the base of the leaf. It includes the first emerging, round-tipped leaf.
It takes 100 to 120 growing degree days from planting to seedling emergence. The growing point is 1 to 1.5 inches below the surface. Seminal roots supply water and nutrients to the seedling. This is the VF stage.
The growing point stays below ground for three to four weeks. Radical and seminal roots grow, and then secondary roots known as nodal roots get started. These grow from nodes below the ground. The first node above the ground is usually the fifth node.
V1 - You will see a thumb-shaped leaf. IF the collar isn't visible, don't include it in staging the plant
V2 - There are two visible collars, generally about 7 to 10 days after emergence. Roots elongate.
V3-V5 - A plant with four leaves with collars is at the fourth leaf stage even though there may be six or seven visible leaves. By V5, ear leaf and shoot start to develop, and tassel is initiated. Plants may be 8 to 9 inches tall, but the growing point is just near ground level.
(Nanda is an independent crops consultant based in Indianapolis, Ind., and director of genetics and technology for Seed Consultants, Inc. Reach him at: [email protected] or call 317-910-9876.)