Good morning! Well, you can certainly tell that summer is winding down. The weeds and wildflowers are in their glory along roadsides, blueberries are everywhere and the blackberries are ripe. Kids are thinking about backpacks and, if you are like me, you have more gardening to do than you want to think about. July was busy and my garden was neglected, hence all the work waiting. Oh well, the garden will go on.
August also tends to be a month when odd problems crop up in the garden. Mildew on garden phlox, blackspot on roses and a general malaise on everything that has bloomed and passed. The weather hasn’t helped. Drought, downpours and much higher humidity than usual have created issues, if my email is any indication.
High temperatures for long periods of time with just occasional thunderstorms do not make for a happy garden. And watering just doesn’t have the same effect as a good drenching rain. I also know that many of you water with overhead sprinklers. When your flowers are subjected to uneven water levels and high temperatures, this weakens them. Add in humidity, plus the fact your plant leaves are wet from sprinklers, and you have a perfect storm for fungal diseases.
Perennials in Maine, thankfully, are usually pretty healthy and don’t develop many of the plant diseases found in other parts of the country. Usually good air circulation in the garden, steady rainfall and our cool nights contribute to an overall healthy garden. But this summer’s drought and humidity have heightened fungal problems.
August is when garden phlox is in its glory — and it is gorgeous. Unfortunately, it is also prone to powdery mildew, a fungal infestation. Roses are susceptible to blackspot, also caused by fungus, especially when using their energy to flower.
You need to identify common fungal diseases, which will spread to other plants in the garden, so you can treat them. Today, we are going to deal with powdery mildew, blackspot, leaf spot on hydrangeas and peony leaf blotch, which ran rampant in spring 2011 but hasn’t raised its ugly head much this year. Who knows why.
Powdery mildew is just that, a fungal disease that makes plant leaves and stems look as though they’ve been dusted with powder. The mildew won’t affect the flowering and it won’t kill the plant, but it does weaken and make it look ugly. It will spread to other plants, although many are resistant. Powdery mildew begins on garden phlox. (You can buy new hybridized plants, such as David and Volcano, that have been bred to be resistant.)
Even though you see powdery mildew in August, it actually begins long before. So if you have plants that get powdery mildew every year, you need to start treating them when the growing season begins.
You can buy a fungicide specifically for powdery mildew or make one. Add 1 teaspoon of baking soda to1 liter of water, shake and spray. Use this about every two weeks and keep the plants well watered at ground level. Because the spores that cause powdery mildew overwinter in the soil, you need to spray the ground around the plants as well as the leaves and stems.
Blackspot is exactly what you’d think — a black spot on the rose leaf. It may start off yellow or brown but will turn black and spread. You can remove a few infected leaves; however, if it is widespread, you will need to treat the bush. Always water roses in the morning, water them at ground level (not overhead) and keep them well watered. There are many commercial sprays for blackspot or you can make your own. Put 3 teaspoons of baking soda, a few drops of dish soap or liquid hand soap and a heaping teaspoon of water soluble fertilizer into a cup of water and shake. Add this to 1 gallon of water in a sprayer and spray every two weeks. This works on both blackspot and mildew on roses. You should start this in early spring and continue throughout the growing season.
Leaf spot on hydrangeas is easily identified as spots of purple, brown or tan. They usually show up later in the season. It will not harm the plant, but if you want to, you can remove the infected leaves or treat it with a fungicide.
Peony leaf blotch is caused largely by lack of air circulation around the plants. If you planted three or four small bushes 15 years ago, they are probably crowded now and don’t get good air flow. Peony leaf blotch starts in early spring as a small, shiny usually purple spot on the top of the leaf with brown spots on the underside. It progresses depending on humidity and heat levels. Take off individual leaves, water from the ground only and treat peonies with the homemade formula for roses or a purchased fungicide. If it is late in the season, simply cut the infected branches to the ground.
In all of these cases, there are a few things to keep in mind. Fungus comes from a spore and spreads through spores. Spores travel in water so if you use an overhead sprinkler (or when it rains), water drops fall onto the fungus and splash spores onto other leaves. For plants with fungus, cut them to the ground in the fall; clean up stems, dead leaves and other debris from the area; and dispose of the clippings in the trash, not in a compost pile where the fungus will live and spread. Cut out any stems on roses that show signs of infection early in the spring and begin the required treatments.
There is always the option of removing plants that are prone to fungal diseases, but I have a hard time doing that. If you don’t, rip away and plant something new.
Until next time, watch for fireflies, picnic by a shady stream and enjoy those flowers you work so hard to make pretty.
Happy gardening.
Jody Goodwin has been gardening for more than 25 years. She lives in Turner with her husband, Ike, and two cats. She may be reached by writing to her in care of the Sun Journal, 104 Park St., Lewiston, Maine, 04243-4400 or by e-mail at jodyike@megalink.net.
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