WASHINGTON -- Now that we are in the height of summer, here's what we can expect to find waiting for us in the garden. There is still planting, weeding, dividing, pinching -- but there's also time every so often to lie in the shade, take in the world around us.
More plants than I can identify are in their July glory. Flowers that opened in June are overlapping with those just beginning to make their show, and annuals are at the top of their game.
This week, I have observed abelia, rose, crape myrtle, goldenrain tree, coreopsis, echinacea (purple coneflower), black-eyed-Susan, day lily, iris, dahlia, liatris, gaillardia, lily, lavender, gooseneck loosestrife (Lysimachia clethroides), hibiscus, canna lily, waterlily, lotus and many annuals.
Continue fertilizing annuals, vegetables and container plants through summer with a water-soluble, balanced fertilizer, such as Peters All Purpose Plant Food or Miracle-Gro. This will increase flower and fruit yield. Fertilize every other watering.
Butterflies are emerging and actively seeking nectar and mates. They will wow you from now until fall. If you failed to plant any butterfly-attracting plants this year, find mature ones at garden centers, such as already blooming hanging baskets or large container-grown specimens. Keep them watered, fertilized and in the sun. Look for verbena, purple coneflower, French marigold, lantana, asclepias, velvet sage (Salvia leucantha) or any other salvia that's in bloom, butterfly bush, black-eyed Susan, coreopsis, cosmos, globe flower (Scabiosa) zinnia and other long-blooming plants that will provide nectar for butterflies. These "flying flowers" will feed well into fall.
You should be noticing hydrangeas in bloom now. Some, such as Pee Gee hydrangea (H. paniculata) and tree, or wild, hydrangea (H. arborescens) are flowering on this year's growth and can be cut to the ground late winter to early spring before growth begins. On the other hand, florist hydrangea (Hydrangea macrophylla) blooms on buds formed last year. The shrub has large leaves and grows about four feet high and wide at maturity. If you want them to flower, don't prune them. Blossoms can be a different color each season.
The color of a florist hydrangea is dramatically affected by soil pH -- acidity or alkalinity -- and now is the time to see that, while they are in bloom. Blue means that the soil is acidic, perhaps as low as 4.5. Pink indicates that the soil is only slightly acidic, a pH of about 6. Leave the current flowers on the plants through winter to protect the bud below. The next lower bud on the stem that bore this year's flower will bear next year's blossom. Vary the pH, and you can change the color. If you want to make it flower pink, sprinkle a half to one pound of pulverized horticultural limestone around the base of the shrub in the beginning of September. Water it well. To go blue, add iron sulfate around the base of the plant in late August and again in September. Water well.
Bearded iris, probably one of the most popular predominantly blue flowering plants, performs best when divided this month, right after flowering. This gives it a head start on next year's growth. Overcrowded bearded irises won't flower well. They should be divided every four to five years. They have distinctive fans of leaves that grow from fleshy, rhizomatous roots. Regular removal of old rhizomes controls iris borers and soft rot that are common to bearded iris. With regular attention, as rhizomes mature, they will be free of borers and soft rot.
Irises grow and bloom from shallow, fleshy roots. When you dig them, the soil usually falls off, and they divide rather easily. Keep only one-year rhizomes (roots) that are attached to a fan of leaves. Dispose of all older root pieces and any showing signs of soft mushy plant parts. The rhizome for transplanting should be about three to four inches long and must have at least one large fan of leaves attached. It's all right if there are a couple of smaller fans as well. Cut the fans in half, to about six inches in length, and transplant to a new location in sun. Make sure that the eye or bud on the rhizome is at or within half an inch of the soil surface, or it won't flower. Use a generous amount of compost.
Joel Lerner is president of Environmental Design in Capitol View Park, Md., and author of "Anyone Can Landscape" (Ball 2001). Contact him through his Web site, www.gardenlerner.com.
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