As June progresses, the corn crops across the Prairies continue to develop and progress. Staging corn plants correctly is essential for understanding and assessing crop development, and when making herbicide, fungicide, and fertility applications and recommendations.

It is important to know the difference between each method as different companies use different methods to make application recommendations. Before discussing the methods of staging corn, it is critical to mention that the first leaf will always have a rounded tip and this leaf needs to be included in the leaf count. As the plant grows and develops this first leaf may die, so be sure to add it to the final leaf count.

Staging Methods

Leaf Collar Method (V-Stage Method)

Counts the number of leaves present with a collar from bottom to top.

• A leaf collar is the lightly coloured band located at the base of an exposed leaf blade, close to where the leaf blade contacts the stem of the plant.
• Leaf stages are described in V stages; a plant with 4 collar leaves is in the V4 stage of development.
  • (Vn, where n = number of leaves with collars)

Leaf Over Method ("Droopy" Leaf Method)

Count all leaves that have arched over (leaf tip is pointing down)/are drooping.

• Start counting at the bottom of the plant and move up.
• Using this method, not all leaves will be counted - the smallest leaves emerging from the whorl are not counted.

Leaf Tip Method

Count all the leaf tips from bottom to top of the plant.

• Young leaves that are emerging from the whorl are included in the count.
• Exercise caution when using the leaf tip method because different hybrids grow differently.
  • For example, some hybrids are bred to have shorter internodes between leaves resulting in more leaf tips present before they flop and are fully functional leaves.

Corn Height Method

Measure from the soil surface to the highest point of the arch on the uppermost leaf with a tip pointing down.

• Note that the highest point on the plant is not being measured.
• This is not the most accurate method to stage corn because corn height can vary depending on environment and management conditions.
• This method is rarely used on its own, so you may come across this staging method paired with other staging methods in provincial Crop Protection Guides, product technology sheets and product labels.

Comparing Staging Methods

Adapted from OMAFRA Publication, 75, Guide to Weed Control.

CHU (Corn Heat Unit) Update

Throughout the growing season, we are going to include a CHU update of six locations across Manitoba, Saskatchewn and Alberta.

Further Reading

• Manitoba CHU Resource - Growing Season Report
• Saskatchewan CHU Resource - Farmwest.com CHU Calculator
• Alberta CHU Resource - Current and Historical AB Weather Station Data Viewer
• Download this blog post as a PDF