Landscape – Effects of Wet Weather

In my line of work, few things give me more opportunity than bad weather. I spent most of last fall blaming the preceding drought for plant problems. Earlier this spring I diagnosed a number of plant troubles based on their exposure to a couple of frigid nights in January.

Now I have the nearly record-breaking rainfall in May to hang my hat on when I’m asked to explain certain garden phenomena. Up in Jefferson, Joe and Dawn Savitsky say that seventy percent of their hydrangea leaves have purple spots, which eventually make a brown hole in the leaf.

Their hydrangeas have cercospora leaf spot, caused by, you guessed it, wet weather! Most of the time a hydrangea can tolerate a good bit of this disease before harm ensues. I usually see it in July, around the time hydrangeas should be pruned, and it typically occurs after a few days of afternoon thundershowers. I rarely advise spraying with fungicide but this year I’ll make an exception because the disease has popped up so early. If you care to spray, use myclobutanil (Immunox(tm)) or mancozeb and avoid overhead watering.

OAKLEAF HYDRANGEA WILT Armillaria root rot is common in landscape plantings of oakleaf hydrangea. The initial symptom is wilting of one or more shoots that previously seemed healthy. Irrigation does no good and within a few weeks the rest of the branches wilt and the plant dies.

Poor drainage is usually the culprit when this root rot attacks. If less than half of your hydrangea is affected, remove the dead limbs, dig it up, add plenty of soil conditioner to the planting area and replant. With a bit of luck it may send forth new sprouts and live to bloom another day.

My colleague Theresa Schrum observed sudden wilting on her oakleaf hydrangea. When she investigated the base of her plant, it was evident that root rot wasn’t the culprit. Voles, the rodent rascals, had gnawed off the bottom of the hydrangea stems. No wonder it suddenly looked so poorly!

MUSHROOMS Mushrooms and other fungi are sure to be common this month. Remember that a lawn mushroom is just the fruiting body of an underground fungus. When excess rain falls, the fungus, which has been happily consuming tree roots killed by last summer’s drought, decides to reproduce. Mushrooms, of varied shape and size, are the result. Many times you can see that they pop up in a semi-straight line, following the belowground root.

One particular mushroom is usually detected by odor rather than eyes. The lattice stinkhorn relies on flies to distribute its spores. What better way to attract flies than with the odor of rotten meat? Folks have reported finding stinkhorns in mulched areas and in piles of wood chips. They do no harm and are fascinating to watch as they develop so I recommend you leave them alone. You can scoop them out with a trowel when your family complains of the smell.

MOSQUITOES This month, and perhaps the entire summer, promises to be filled with complaints about mosquitoes. I know that the propane-fueled mosquito traps can catch a ka-jillion of the hungry creatures but remember that the common Asian tiger mosquito is resistant to the attractant in these machines. If my yard has one thousand mosquitoes and the machine is ninety nine percent effective, there will still be ten mosquitoes hovering around my ears and ankles.

I keep spray bottles of DEET-containing mosquito repellent positioned in handy spots throughout my back yard. I encourage you to do the same for the foreseeable future.

I’m sure many more plant and insect problems will pop up as a result of the May rains. Fortunately, as summer turns dry, soggy situations will disappear…and I’ll begin my familiar refrain of “Well, drought damage can take many forms. If it weren’t so very dry right now, your plants would be fine!”