As always, our summer weather has proven to be the wild card in the success of my garden this year. For the past few years, it has been very dry making constant watering a must. However, I saw very little evidence of disease other than some common issues such a black spot on my roses and powdery mildew on my asters. While unsightly, neither has caused major problems for me.
This year, however, our early unseasonably warm temperatures and high humidity have created a whole crop of issues that are proving problematic. Most of these problems have affected my container gardens in ways that I have not ever had. Most of my perennials are doing well but I am also having issues with some trees and shrubs. All in all, it's one of the more problematic summers I've had in the garden.
A couple of years ago I had a terrible problem with aphids. Mostly they infected several plantings of cosmos I had around the house and fortunately only one container. At the time, someone told me that it was our very hot AND DRY weather that was causing such a huge crop of aphids. This year, it seems aphids have been everywhere as well. I have pretty much had them on almost every container on my deck. Fortunately they've been easy to deal with. A little insecticidal soap usually does the trick for me.
However, since it's been so humid I had to wonder just how accurate my information about aphids was. Turns out it was half right. It's merely the high temperatures that create several generations of aphids in a season. Seems the humidity, or lack of it, isn't really the issue.
After I got rid of the aphids my plants didn't seem to bounce back as well as they should and I have had several die. I should mention here that this is often the point where many gardeners blame themselves for their lack of gardening know-how. I, too, have done this and have assumed that I somehow have killed all these plants. Sometimes, yes, it is user error. Sometimes I forget to water. Some people water too much and literally drown their plants. But sometimes, you do all the right things and still, you have dead plants.
With all the excessive rain and humidity this summer, watering my container gardens has been a challenge, particularly on my deck. My deck gets the morning sun and is in shade for the afternoon and evening. It does tend to be windy as well. However, I have had trouble getting the containers to dry out. Or so it seemed. I stopped watering because of this and because I noticed that I was getting stem rot in my begonias. I've grown begonias successfully in pots for years and was getting really frustrated that the begonias were dying off. The containers finally dried out and the begonias continued to rot.
A little research revealed that what I have is powdery mildew. Powdery mildew is a fungus that can affect many different plants. Guess what the ideal conditions are? Yep, high humidity. The only good thing about powdery mildew (if there can even be such a thing) is that each strain is specific to its host. Which means if you have powdery mildew on your begonias, it won't spread to other plant species. Which is not to say that they won't have their own powdery mildew as well.
So far, I have lost my trailing violas and some pansies (although whether that's powdery mildew, aphids or something else, I don't know) and all my tuberous begonias. I also have a fungus of some sort on the Ribbon Bush and my lysimachia is all curled. Seems like it's time to try a fungicide. A quick internet search shows two readily available retail products. One is a neem oil based product called Shield All II Broad Spectrum Fungicide. The other is a organic product called Seranade Garden Disease Control.
The other problem our excessive rain has caused is chlorosis in several of my trees and shrubs. Clay soil plus alkaline ph plus heavy rain seems to equal iron chlorosis problems from what I can figure out. Iron chlorosis is when plants don't get enough iron from the soil. The most noticeable symptom is that the leaves turn yellow. Clay and alkaline soils are prone to this anyway. I think the rain just makes it worse. Probably because the tree is under further stress from overwatering.
At any rate, I've applied Miracle Grow for Acid Loving Plants to my shrubs with good results. The acid in the fertilizer helps release the iron in the soil and also has chelated iron. My shrubs have noticeably greened up in the last coupe of weeks. My trees on the other hand have been slower to respond. I may not notice an improvement until next year.
How is your garden growing? What problems are you seeing? What's doing especially well for you?
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