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Track corn growth into critical stages

Corn Illustrated: Big changes occur within plants as tasseling and silking approach.

Tom J Bechman 1, Editor, Indiana Prairie Farmer

June 7, 2022

3 Min Read
Tiny ear of corn that has not emerged from within the plant
FIND THE EAR: Note that a small ear exists within this plant, even though it has not fully emerged yet. This plant was approaching the silking stage. Photos by Tom J. Bechman

People are amazed during corn’s grand growth phase, when you can literally watch plants grow overnight. That typically occurs between V8 and V10, which is the eight-leaf stage to 10-leaf stage, or about waist high. Yet nothing compares to the miracle that occurs when corn reaches tasseling, silking and pollination.

Once a corn plant reaches the 12- to 14-leaf stage, split the stalk carefully, and you will find a tiny tassel forming.

“You can also find an immature ear at the node where the main ear will form,” says Dave Nanda, director of genetics for Seed Genetics Direct. “Eventually, this ear inside a husk separates itself from the stalk, and silks begin emerging.”

Once silks emerge, the corn plant is officially in the R1 reproductive stage. The miracle of pollination is underway, Nanda says.

Here are seven facts about pollination. For more details, refer to the Purdue University Corn & Soybean Field Guide.

1. Silk emergence. This is the first recognized stage of the reproductive process, which the plant has prepared for during its entire life. The stage technically begins when any silks are visible outside the husk.

Silks peeking out of the ear shoot on a corn plant

Silks are just peeking out of the ear shoot on this plant. Since silks are visible outside of the husk, this plant would be classified as at the R1 stage.

2. Silk growth. Silks grow an average of 1.5 inches per day during the first few days after emerging from husk leaves. “Each silk grows until it is fertilized by a pollen grain shed by the anthers in the tassel,” Nanda says.

3. Life of silks. Silks typically remain receptive to pollen for up to 10 days. If pollination doesn’t occur, silks keep growing, but eventually deteriorate with age.

4. Pollination. Pollen grains captured by silks germinate and develop pollen tubes. They penetrate silk tissue and elongate to reach ovules within 24 hours. “It’s a delicate process, and why it’s critical to have favorable weather — not too hot or excessively dry — for successful pollination,” Nanda says.

5. Pollination order. Ovules at the butt of the ear are fertilized first. Pollination progresses to the tip, which is pollinated last.

small corn ear from plant nearly at R1 stage lying on truck bed next to ear from an R1 plant

The small ear on the left was taken from a plant not yet fully at R1 stage. The ear on the right is from an R1 plant. Silking was occurring, but silks were still attached to this ear because ovules were not yet fertilized.

6. End of silks. Once an ovule is fertilized, the pollen tube collapses, and the silk falls away. “It’s the basis for the shake test,” Nanda says. “Carefully remove an ear with silks from the husks, hold it out and shake it. If silks fall away, those ovules are fertilized, and kernels will form. If silks remain, fertilization hasn’t occurred yet.”

7. Silking issues. If plants are under heat and/or drought stress, the nick between pollen shed and silking may be off. If pollen shed occurs too late, and silks are no longer receptive, kernels won’t form. Sometimes when silks emerge early in aggressive hybrids, kernel set around the butt of the ear may be sporadic until pollen shed occurs.

About the Author

Tom J Bechman 1

Editor, Indiana Prairie Farmer

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