Photo: Powdery Mildew (courtesy of The Missouri Botanic Garden)
Extreme weather conditions and the Chicago-land area are no strangers. So why it is so shocking to homeowners when their landscapes don’t look like the gardens at Buckingham Palace? Because most of the time, it takes weeks and sometimes even months after the harsh weather conditions before a plant shows signs of weakness and stress, and by then, homeowners have long forgotten about the 12 feet of snow, 6 inches of rain or extreme high humidity. And to make matters even worse, by then it’s often too late to offer proper treatment. So what do we do?
Ideally, learn how to forecast the weather months in advance.
If weather-related fortune telling isn’t your forte, consider using preventative spray applications, proper watering practices, and selective pruning methods to minimize extreme weather-related stress. Most of the damage we see right now are fungal leaf spots from all the rain we had this season. But don’t worry; although these spots are unattractive, they are not harmful. You do have an issue if the leaf spots are accompanied by early leaf drop, which puts a lot of stress on the plant (see below).
On maintenance sites, remember to take good notes on the history of the landscape and what looks good and bad and when. These notes can be used to forecast what diseases and pest issues will probably reoccur yearly. For new installations, plant disease resistant varieties.
Below is a seasonal breakdown that is meant to be used as a guide for plant care.
Prune out dead wood (make sure pruners are CLEANED after every cut) in late winter/early spring
Apply preventative fungicides (before the infection occurs) at bud swell and continue according to fungicide directions (usually a minimum of three applications)
Water when necessary on a slow drip (avoid all overhead watering)
Rake, remove and dispose (do not compost) diseased leaves and twigs of plants that have dropped
Spray for powdery mildew as soon as symptoms appear (check label for directions)
Spray rust-susceptible junipers (in early July) and remove galls and cankers to reduce infection of other rust hosts
Continue watering when necessary on a slow drip
Continue raking and disposing of diseased leaves and twigs
Spray broadleaf evergreens with anti-transpirant
Water new plantings on warmer days if soil is dry
Crabapples can be pruned, if necessary (make sure pruners are CLEANED after every cut)
Pruning of deciduous shrubs (current year bloomers prune in late winter/early spring, previous year bloomers prune after spring flowering) to encourage air circulation and new growth