The arrival of cool temperatures reminds us that it won't be long before perennials will need covering for winter protection. Overwintering perennials for the first time? The process for successful overwintering begins with healthy plants.
Cool night temperatures, warm day temperatures and heavy dew are favorable for many foliar diseases including Bacterial leaf spot, caused by Pseudomonas cichorii on garden mums. Symptoms appear as black spots on foliage concentrated at the base of the plant. The spots often begin at the leaf margin but may also occur randomly. The spots are soft when tissue is wet and sunken and brittle when leaves dry. From the leaf, the bacterium can move through the petiole and into the stem resulting in a canker.
The familiar imported cabbage worms adults can be seen fluttering above ornamental cabbage and kale. The adult is a white butterfly tinged with yellow on the underside of its wings.
Monitor root health and test growing media of garden mums. Take random samples of plants out of their pots and examine roots carefully. The roots tell a lot about overall plant’s health, often before the top growth shows symptoms. Signs of poor root health are blackened or rotted roots or the lack of roots, especially young feeder roots. Diseased roots will not take up fertilizer.
Note: The 2015-2016 New England Greenhouse Floriculture Guide will contain a new section “Protecting Bees and Pollinators from Pesticides”. Contributors to the new section are Dr. Richard Cowles, The Connecticut Agricultural Experiment Station, Dr. Raymond Cloyd, Kansas State University, Dr. Kimberly Stoner, The Connecticut Agricultural Experiment Station, Dr. Lois Berg Stack, University of Maine and me. The new guide will be available November 5&6 at the Northeast Greenhouse Conference. Tina