Wednesday, October 31, 2007

Greenhouse - Calcium Deficiencies in Poinsettias Causes Bract Burn

A common problem in poinsettias is calcium deficiency. The following are pictures and information on this problem.

Bract and leaf edge burn caused by calcium deficiency. Photo by Paul V. Nelson, Professor of Horticulture, Department of Horticultural Science, North Carolina State University

In October, during cloudy weather, light quality decreases and we often see a slowing of movement of calcium from the substrate into poinsettia leaves and bracts. If calcium does not move properly into the foliage, the deficiency will show up as bract edge burn in November and December. Many growers switch to mainly calcium nitrate based fertilizers and make foliar applications of calcium chloride to strengthen stems and prevent bract edge burn. Applying a fine mist of 200-400 ppm calcium chloride with a spreader sticker once a week is recommended. Final growth regulator applications should also be made by late October to avoid a decrease in the bract size.

Article modified from the Greenhouse TPM/IPM Weekly Report, University of Maryland Cooperative Extension, October 19, 2007 edition.

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