Lower Leaf Yellowing and Purpling in Spring Pansies
Over the past few weeks, the
Midwest has experienced many cool and rainy days. These conditions create an
opportunity for lower leaf reddish purpling to manifest in early spring crops
such as pansy (Viola × wittrockiana). While on a recent grower
visit, I noticed lower leaf yellowing (chlorosis) and reddish purpling. When
these symptoms arise, you should first inspect the roots or submit samples to your
preferred diagnostic lab for pathogen testing. In-house, you can perform a
PourThru to determine the level of soluble salts [referred to as electrical
conductivity (EC)]. Low substrate EC often causes lower leaf chlorosis. Target
substrate EC levels for pansies range between 1.3 to 2.0 mS/cm based on the
PourThru method. Providing 100 to 150 ppm N should prevent lower leaf chlorosis.
Additionally, maintain a substrate pH of 5.5 to 5.8 based on the PourThru method.
Lower leaf purpling is often attributed to the lack of phosphorous. In this
case, cool air temperatures and saturated substrate with limited fertility likely
induced the symptoms. Drying out the substrate, increasing growing temperatures,
and providing proper fertility will help correct this disorder if a pathogen is
not suspected. For crops grown outdoors, frost blankets or floating row covers
work well at night or during cold snaps.
W. Garrett Owen
Assistant Professor of Sustainable Greenhouse and Nursery Systems, The Ohio State UniversityW. Garrett Owen is an Assistant Professor of Sustainable Greenhouse and Nursery Systems in the Department of Horticulture and Crop Science at The Ohio State University. He has an appointment in research, teaching and Extension. His area of expertise is plant nutrition; plant growth regulation; and production problem diagnostics.
