The morning of Monday May 10 saw widespread frost across the area with temperatures dipping to -5 in the early morning hours. Later in the day, corn was looking similar to this picture and by the end of the day all leaf tissue had totally blackened and disappeared. The extent of damage depends on many factors, including soil type and topography, to name just two.
The picture below, taken on Wednesday May 12, illustrates the fine line between no damage and apparent death.
Beside this mature windbreak of 20' tall evergreens, the corn plants survived. This effect extended out 20 rows or 50' from the edge of the windbreak. The rest of the field is barren, no corn and no weeds. This actually is backed up by research that predicts the positive effect of a windbreak to be 2.5 times the height of the windbreak. But on a frosty night there is little to no wind and we may wonder why we still get the benefit of the windbreak. This is because the living trees give off enough trapped heat to warm the surface temperaure of the soil and this slight temperature difference was enough to protect the crop from frost damage. The weeds between the rows are also doing fine, but that will be easy to fix.
I believe the corn crop will survive and regrow. The next picture is a plant taken from our own field, which had emerged and was at the two leaf stage before the frost. On Tuesday I brought a few plants inside to warm up. This picure was taken Thursday morning, 72 hours after the frost and 48 hours after being brought inside and kept at 20 degrees.
You can see the new leaf growth emerging from the whorl, which indicates the growing point is still alive and well. I will post a picture tomorrow to show what another 24 hours of warmth will do. It has been too cold and wet this week to see much growth recovery in the field, but I remain confident corn will show some life this weekend when it warms up.
I have been asked what effect this frost has on yield and this is a difficult question to answer. The balance of the growing season will have more impact on yield than this frost. One thing we do know, it will impact maturity somewhat. The plant was shocked and it takes some heat, maybe 30-50 heat units, to put the plant on the road to recovery. This heat would have been put to use in advancing growth under normal circumstances, but now has been used for recovery.