DETERMINING CORN GROWTH STAGES FOR ESTIMATING YIELD LOSS DUE TO DEFOLIATION
LEAF STAGE DEFINITIONS FOR CORN
There is no standard method for leaf staging corn. The two most widely used methods are easy to learn. Both methods begin counting leaves with the first true leaf (short and rounded tip).
The Leaf Collar Method
This method is the one preferred by most university agronomists. Only leaves with visible leaf collars are counted. The leaf collar is the off-color green "band" at the base of the leaf blade, near the stem of the corn plant. If a plant has three visible leaf collars, then it is described as leaf stage V3.
Start with first oval-shaped leaf as V1. Field defined as being at a given stage when at least 50% of plants show collars.
Field corn developmental stages -- based on the Leaf Collar Method
| Vegetative Stages | Reproductive Stages | ||
|---|---|---|---|
| VE | Emergence | R1 | Silking | V1 | First Leaf | R2 | Blister | V2 | Second Leaf | R3 | Milk | V3 | Third Leaf | R4 | Dough | V(n) | Nth-node | R5 | Dent | VT | Tasseling | R6 | Physiological maturity |
The Horizontal Leaf Method
This method is most commonly used by crop insurance adjusters and is the one referred to in the D efoliation Yield Loss table on page 6 of this guide. It differs from the Leaf Collar Method in that leaf collars are ignored. The last leaf that is counted is the uppermost leaf that is 40 to 50 percent exposed from the whorl, with a leaf tip usually beginning to droop down or pointing below the horizontal.
1. Identify uppermost leaf that is 40 to 50 percent exposed and whose tip is below the horizontal.
2. Typically, a "horizontal leaf" growth stage will be 1 to 2 leaf stages greater than the collar method.
A timeline for corn growth and development
| Growth | Approx. | Cum. | Calendar | |
| Stage* | GDDs** | GDDs | Date | Planting | May 1 |
| VE | Emergence | 100 | 100 | May 10 |
| V3 | 3 leaves | 180 | 280 | May 24 |
| V6 | 6 leaves | 180 | 460 | Jun 4 |
| V9 | 9 leaves | 180 | 640 | Jun 14 |
| V12 | 12 leaves | 180 | 820 | Jun 23 |
| V15 | 15 leaves | 180 | 1000 | Jun 30 |
| V18 | 18 leaves | 180 | 1180 | Jul 8 |
| VT | Tassel | 60 | 1300 | Jul 13 |
| R1 | Silking | 60 | 1360 | Jul 15 |
| R2 | Blister | 300 | 1660 | Jul 27 |
| R3 | Milk 200 | 1860 | Aug 5 | |
| R4 | Dough | 140 | 2000 | Aug 11 |
| R5 | Dent | 300 | 2300 | Aug 25 |
| ½ Milkline | 220 | 2520 | Sep 5 | |
| R6 | Black Layer | 200 | 2720 | Sep 17 |
* Based on leaf collar
method as defined by Ritchie et al. (1986), "How a corn Plant Develops," Spec.
Rep. #48, Iowa State Univ.
** Approximate growing degree days (GDDs) between growth stages.
Comparison of the Two Leaf Staging Methods.
A simple relationship exists between the two methods of leaf staging. For corn that is younger than about 5 leaf collars, the Horizontal Leaf Method will usually result in leaf stages that are one greater than the Leaf Collar Method. For example, if the Leaf Collar Method results in a leaf stage of V3, the Horizontal Leaf Method would likely result in a 4-leaf stage.
For corn that is older than 5 leaf collars, the Horizontal Leaf Method will usually result in leaf stages that are two greater than the Leaf Collar Method. For example, if the Leaf Collar Method results in a leaf stage of V6, the Horizontal Leaf Method would likely result in a 8-leaf stage.
When Lower Leaves are Missing Lower leaves on older plants usually disappear, making leaf stage determination difficult. Staging older corn begins by first splitting the stalk neatly down the middle and looking for the first noticeably elongated stalk internode. This internode is usually 1/2 to 3/4 inch long (see Fig. 1 on the next page). Carefully identify the leaf whose leaf sheath attaches to this node. The 5th leaf is usually attached to the node above this elongated internode. Continue counting the remainder of the leaves with leaf collars to complete leaf stage determination of the plant.
ligule, leaf blade and leaf sheath