The Garden Guru: Summer in the perennial garden

Posted Saturday, Jul. 06, 2013  comments  Print Reprints
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By now, all the daffodils and grape hyacinths are faded memories. Roses have finished blooming until fall, except for occasional smaller and oft-faded blossoms. Iris and even day lilies have wrapped up their runs for the season, and we’re left with perennial gardens that are suddenly looking a bit worse for wear.

What can we do now to bring them around? What can we plant, and what should we be doing in mid-summer to have even better results this fall and next spring?

Your first goal in any perennial garden in July will be to remove spent flowers and seed heads. Gardeners call it “deadheading,” and its sole purpose is to keep things looking tidy. Sometimes it also involves clipping yellowed leaves and pulling dried and crisp foliage.

If day lily flower stalks are still green, clip them off just above where they go into the clumps of foliage. If they’re completely dried and shriveled, you can probably remove them with a gentle tug. If iris leaves have started to turn brown at their ends, use sharp grass shears to trim them back to the edge of the green tissues, but don’t remove leaves or portions of leaves that are still green. They’re busy storing nourishment for upcoming seasons.

Your next big responsibility with perennial plantings is to remove all the weeds. Broadleaf weeds (nongrassy) can easily be pulled when the soil is moist. Annual grasses like crabgrass can also be cultivated or pulled. Bermuda grass in particular, however, will have to be sprayed. Use one of the glyphosate-only herbicides, and spot-treat by holding a piece of cardboard as a baffle to protect the good plants while you operate the pump sprayer with your other hand. The glyphosate weedkillers are not active in the soil, so they aren’t taken in by your perennials’ roots.

Mulch the beds to conserve moisture and slow additional weed growth. There are many good choices in attractive mulches, even including compost you’ve generated yourself from your garden and landscape. I am fond of finely ground (nickel- and dime-size) pine bark mulch, but use whatever type appeals to your eye.

Most Texas perennials have deep roots as a means of surviving their more stressful times. That means you need to water them deeply when you do irrigate, then wait until the top of the soil begins to dry to the touch before you water again. Drip irrigation lines can work well, but it’s best to lay them in place in fall or early spring, so plants can have months to establish new roots near the emitters. For now, low-angle sprinkler heads will keep water from blowing and evaporating badly, plus they’ll apply the water uniformly across the entire root areas.

If you have spots in your perennial plantings that are bland-looking between bloom cycles, perhaps you could plug in some annual color as a supplement. We have several outstanding choices of annuals that can stand up to the heat, even as fresh transplants. That includes cooper plants, firebush, pentas, angelonias, purslane, moss rose, vinca (the ‘Cora’ series is most disease-resistant), ‘Profusion’ zinnias, melampodiums and Dahlberg daisies. Of course, you’ll want to prepare suitable soil for these small “pocket plantings” among your perennials, and you’ll need to water them by hand daily for the first couple of weeks to get them established.

Some garden centers, particularly independent retail nurseries that specialize in perennials, will have types you can plant in mid-summer. You’re likely to find several types of gloriosa daisies (‘Goldsturm’ is one of the best at establishing and spreading), hardy hibiscus (mallows) with flowers as big as dinner plates, cannas (especially the highly variegated types that are grown primarily for foliage) and summer phlox.

We have 30 or more types of salvias that are currently being grown and sold in the nursery industry. Shop at several nurseries, and you’re likely to encounter many summer-flowering types. Salvia greggii is the most popular, mostly because of the fact that it’s almost shrublike in its permanence. It starts flowering in March and blooms until frost. However, in mid-summer, it takes a short vacation, and that’s the time you want to give it a light trim. Remove as much as a third of its top growth in late July or early August to keep the plants compact and vigorous. Other salvias should only be trimmed as needed to remove spent flower stalks. With that done, many of them will keep blooming through additional cycles.

Neil Sperry publishes “Gardens” magazine and hosts “Texas Gardening” from 8 to 11 a.m. Sundays on WBAP AM/FM. Reach him during those hours at 800-288-9227 or 214-787-1820.

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