Cool and wet weather at early stages of corn development, as we have experienced this year, are ideal for the appearance of purple plants.

So what else causes corn plants to become purple? Some of the reasons are given below:

• Purple leaves are caused by a pigment called anthocyanin. When sugars produced by the chlorophyll cannot be deposited in the growing stalks, leaves, and roots, they are converted to anthocyanin pigment which is red to purple in color.

• Acidic soils with pH lower than 5.5 may also cause purpling of the seedlings.

• Wet soils like this spring can also inhibit the nutrient uptake and cause purple leaves.

Many causes of purpling: Corn plants short on phosphorus turn purple; that's a true statement. But the effect may be due to many reasons, including soil compaction, not just a real shortage of phosphorus in the soil. (Photo courtesy Scott Gabbard, Shelby County Extension)

• Purpling generally occurs between V2 to V5 stages of growth. By V8, purple leaf syndrome disappears and color becomes normal healthy green again. 

• Any plant stresses which reduce uptake of phosphorus may also result in purple leaves and stalks. Root restrictions may also cause phosphate deficiency symptoms.

• Purple leaves may also indicate real phosphate deficiency in the soil.

• Soil compaction can make it difficult for the small roots to penetrate and absorb nutrients and seedlings show phosphate deficiency symptoms.

• Warmer days and cool nights can also cause purpling of leaves. Sunny and warmer temperatures help in the development of green color.

Related: Purple Corn: Now You See It, Now You Don't

• Even in the adult stages of growth, if sugars produced by leaves cannot be deposited into the ears because of insect damage in the stalks such as corn borer holes, it gets deposited in stalks as reddish to purple anthocyanin.

• Herbicide and insect injury can also cause stress and purple leaves.

• Genetics of some hybrids tends to exhibit purpling at the seedling stage which later disappears. However, purple color does not cause slower growth in seedlings and yield reduction.

Nanda writes from Indianapolis. He is a consultant for Seed Consultants, Inc. Email [email protected] or call 317-910-9876