Purple Stalks at Harvest

Bob Nielsen, Extension Corn Specialist, Department of Agronomy, Purdue University

Corn growers are accustomed to seeing purple corn plants early in the spring following days of bright sunshine and cool nights (http://www.kingcorn.org/news/timeless/PurpleCorn.html). Sometimes plants turn purple during the grain fill period if kernel set has not been successful or if ear development is arrested by some sort of stress (http://www.kingcorn.org/news/timeless/PurpleCorn2.html). The physiological reason for purpling early in the season or late in the season is the same and is a biological response of the plant to excessive photosynthetic sugars concentrating in the leaves or stalks. Early in the season, the sugar buildup is in response to incomplete use of photosynthetic sugars created during the day due to poor root development. Late in the season, the sugar buildup in the leaves and stalks is in response to too few developing kernels in stressed plants. Barren plants (no ear or ears with no kernels) at harvest often continue to exhibit the purple or red pigmentation in the outer stalk tissue near or below the ear.

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