The early start to the corn season came to an abrupt halt in parts of Ontario on May 23rd when temperatures dipped to -3oC in parts of the province. It is always painfull to see corn seedlings flat on the ground (Figure 1.). However, with corn mostly at the spike to 4 leaf stage when hit by frost, the plant’s growing point was still below ground, limiting frost damage to the aboveground parts of the plant. With its growing point intact, within 2 to 5 days of the frost (Figure 2.), corn will start to put out new leaves.
Figure 1. Frost Damaged Corn Stand (click to enlarge image)
Figure 2. Corn Seedling Showing New Growth (click to enlarge image)
Corn past the 4th leaf stage is at greater risk of frost damage since the plant’s growing point is close to the soil surface and is more easily damaged by frost. Additionally, older plants damage by frost will be left with a large amount of dead leaf material in the whorl of the plant. This dead tissue can prevent the extension of new leaves. Past attempts at removing the dead material by clipping the top of dead plants (haybines, riding lawn mower, etc.) to allow the new growth to push through the damaged whorl have generally not been successful.
For information and tools to assist with replant decisions see:
Plant Populations at Various Row Widths
Replant Decisions, Agronomy Guide, Pub 811
Replant Decision Aid 1.8, GOCorn.net