What to do in your garden in August
• Fill color gaps When summer perennials finish blooming, cut them back and ― between the remaining foliage rosettes ― plant heat- and drought-resistant Madagascar periwinkle (Catharanthus roseus). This tender perennial blooms until the first hard frost. Look for reliable performers like the Heatwave series in shades of deep rose and bicolored peppermint. Or try new 'First Kiss Blueberry' with violet-blue flowers or 'Titan Lavender Blue Halo'.
• Start veggies for fall harvest Sunset climate zones 2b, 3b: When summer vegetables stop producing, pull them out and prepare the soil for a second planting for fall harvest. Before planting, dig several inches of compost into soil amended with all-purpose fertilizer. Then sow seeds of fast-growing varieties of cool-season vegetables, including beets, carrots, radishes, salad greens (arugula, loose-leaf lettuce), spinach, and Swiss chard. Keep the soil moist until the seeds germinate, then mulch around plants with 3 to 4 inches of hay, straw, or pine needles. Botanical Interests offers a large selection of seeds of cool-season vegetables, including 'Baby Little Fingers' carrot and 'White Icicle' radish.
• Try a species peony Fall is the preferred time to plant all kinds of peonies. Most herbaceous peonies are hybrids, which need lots of sun to grow well. Many of the species peonies are more tolerant of shade. One of the best is fernleaf peony (Paeonia tenuifolia), which displays deep red flowers with yellow stamens over finely cut leaves. Other candidates include P. obovata, with white to rosy purple flowers, and P. veitchii, with bright pink flowers. One source offering a large selection of species peonies is Rice Creek Gardens (763/754-8090).
• Control spider mites These tiny pests can be particularly troublesome during hot, dry weather, causing speckled or bronzed leaves that fall prematurely. Blast the mites off plants with a strong jet of water from a hose. Spraying insecticidal soap and dusting with sulfur can also help control them.
• Feed hummers Set out feeders filled with sugar solution now to entice hummingbirds to visit for a few weeks before they begin their fall migration. Place the feeder in an open area and tie red ribbons onto nearby branches to attract birds. Be sure to keep the feeder clean and refill it with fresh solution every day or two. For details on cleaning feeders and a recipe for sugar solution, go to www.valleywild.org/hummer_feeding.htm
• Harvest crops The best way to tell when apples, cherries, grapes, peaches, plums, and raspberries are ripe is to taste one; pears can be picked green and ripened indoors. Harvest carrots when they are an inch across at the top of the root. Corn is ripe after silky tassels turn brown and when a kernel pierced by a fingernail exudes milky juice. Eggplant is best when firm and plump, while the skin is still glossy. Ripe melons smell sweet and separate easily from stems. Dig potatoes when the plant's top dies back. Leave pumpkins and winter squash on the vine through the first light frost, then cut and cure fruit on the ground for 7 to 10 days before storing.