Reddish-purple coloration

Phosphorus deficiency can be caused by poor soil phosphorus availability, which is enhanced by cool, wet growing conditions. Sunny days and cold nights can also contribute to the development of coloration similar to phosphorus deficiency. In addition, some hybrids can naturally develop a reddish-purple coloration early in the season regardless of plant phosphorus status. A soil fertility test is one of the most definitive tools used to confirm this situation.