Its official: The fun part of the season is over. Those enchanting hours of perusing the nurseries, planning new beds and watching them take shape have given way to the sweaty work of maintenance. Perhaps youd rather be inside with a cold beer cheering on Michael Phelps, but remember: It only takes a few weeks of neglect for your urban oasis to deteriorate into a sad wasteland.
Pests and Diseases
August is the month when mildew mars the leaves of many plants, especially phlox, zinnias, chrysanthemums, bee balm, peonies, and lilacs. The best way to avoid powdery mildew is to keep the leaves dry and the soil evenly moist. Spray susceptible plants weekly with garden sulfur or copper fungicide. When buying these plants, look for mildew-resistant varieties.
Black or brown spots on clematis leaves indicate fungal leaf spot. Remove affected leaves, cut back any blackened stems to healthy tissue, and spray vines weekly with fungicide.
Scale insects also flourish in the summer. Infested plants often look sickly, with yellowing leaves that may drop prematurely. Check the undersides of leaves for scale, which look like small, waxy bumps. They may be gray, brown, or white, and range in size from less than 1/16 of an inch up to 1/4 inch. Some species excrete a sticky honeydew. Spray the undersides of infested leaves with a mixture of 1 tablespoon commercial insecticidal soap concentrate, 1 cup isopropyl alcohol, and 1 quart water. Spray every three days for two weeks.
Deadhead all blooming perennials. Cut off spent flowers individually if there are still unopened buds on the stalk; cut to the first leaf joint below the dead blossom if the flowers grow on individual stems. Cut flowering stems to the ground once blooming has finished, but leave green foliage intact
Pull up any perennials that have strayed beyond their intended boundaries. Keep a close eye on black-eyed Susans, yarrow, ornamental grasses, Lysimachia (gooseneck loosestrife and creeping jenny), and Oenothera (evening primrose and sundrops).
Feed chrysanthemums, asters, autumn blooming anemonies and lobelias, monkshood, and any other perennials that have not yet bloomed.
Give all your plants a boost by spraying the leaves with liquid seaweed at the rate of 1 tablespoon to one gallon of water. The aroma is temporarily gag-inducing, but your plants will be visibly healthier and more productive.
Just when all those hours of watering and tying up the tomatoes are starting to pay off, you might find yourself competing with wildlife for your prize vegetables. If critters are getting the best of your crops, its time to take up arms. To keep the squirrels away, mist vegetables weekly with hot pepper spray (available commercially, or mix 1/2 cup finely chopped hot peppers with one pint of water and strain before using). Prevent insect damage by spraying with a commercial neem oil. Re-apply after rain.
Finish planting cool season vegetables this month. Swiss chard, turnips, spinach, lettuce, and peas can be planted now and, if you hurry, you can also get in one last crop of green beans.