Gardening Rx > Cool Plants for Hot Places

We can’t always count on Mother Nature to deliver the right amount of rainfall when we need it. One hot, dry spell can wreak havoc on a lush summer border, and yet some plants seem to thrive on neglect and easily adapt to searing heat. Look at the tough rugosa roses that flourish along our sandy seashores or the rugged alpine plants that survive Mount Washington’s extreme weather. When planning a drought-defying summer garden, landscape horticulturalist Scott Burns of Meredith recommends following nature’s lead.

Native plants have evolved in this climate and are suited to our growing conditions. “Nature dictates what works. If you want plants that can stand hot, dry conditions, look at an old gravel pit and see what comes in naturally,” Burns says. It is common to find drought-tolerant native plants and wildflowers such as black-eyed Susans, sweetfern, milkweed or goldenrod reclaiming such wastelands.

Plants native to the hot dry areas of the world—such as the Mediterranean coast, South Africa, Australia and our own prairie-and-desert Southwest—are naturally adapted to arid conditions. Some are not winter-hardy in New England and have to be grown as annuals, but many are tough-as-nails perennials that are not only drought-tolerant but also have attractive foliage, bloom for a long season and are not bothered by pests or diseases.

Top Picks

Top picks Ten summer-blooming perennials for the hot spots in your garden are:

¦ Achillea. Yarrow is a fast-growing perennial that can withstand drought and infertile soil. Several cultivars to look for include ‘Moonshine’, which grows to be about eighteen-inches tall with lemon yellow flowers that are good for cutting or drying. It has attractive finely cut, gray foliage. ‘Coronation Gold’ is a taller variety—reaching three feet—with bright yellow flowers, and shorter ‘Oertel’s Rose’—growing between one and two feet tall—has purple-pink flowers. ‘Summerwine’, an A.millefolium type, has burgundyred blossoms. All are easily grown, bloom from June through September, and can be readily divided.

¦ Asclepias tuberose. Butterfly weed is a long-lived native plant in the milkweed family. As a tap-rooted perennial, once it is established, it should not be moved. Bright orange and yellow flowers make it irresistible to butterflies. Growing between two and three feet tall, it will bloom over a long period, beginning in late spring and continuing through late summer.

¦ Coreopsis verticillata. ‘Moonbeam’ is a compact, thread-leaf variety with lacy foliage and pale yellow flowers. ‘Zagreb’, also compact, grows to between twelve and eighteen inches with brighter yellow blossoms. Both bloom continuously if deadheaded. Although delicate-looking, these are rugged, dependable plants that are native to dry coastal areas. Burns calls them “bulletproof.”

¦ Echinacea purpurea. A tough prairie native, the coneflower is the queen of low-maintenance gardens. It blooms with long-lasting, purple, daisy-like flowers borne on a sturdy three- to four-foot-tall stem that can withstand the harshest wind and weather. Echinacea purpurea self-seed and are reliable performers that bloom despite heat or drought. Sue Anderson of Mason Hollow Nursery in Mason suggests trying some of the new colored coneflowers, such as bright orange ‘Sundown’, vibrant orange-red ‘Sunset’ and palegreen double ‘Coconut Lime’, which she says is fabulous. For something different, Anderson recommends the unusual ‘Green Envy’, which is green with a purplish center cone, or ‘Pink Double Delight’, a compact plant reaching only between eighteen and twenty-four inches tall but bearing multiple, bright pink, double flowers per stem.

¦ Echinops ritro. Globe thistles are tough, tap-rooted plants that grow to be about four feet tall, and have round, spiny, purple flowerheads and jagged gray leaves. Great for architectural quality, Echinops ritro combine well with other drought-tolerant plants but are showy enough to stand alone. A favorite of bees and butterflies, once established globe thistles are long-lived and heat resistant.

¦ Gaillardia grandiflora. This is called “blanket flower” because the plants are blanketed with flowers all summer long. Look for All America Selections (they recognize only a handful of hardy flowers every year) winner ‘Arizona Sun’, which has wide, mahogany-red petals tipped with yellow, or ‘Fanfare’ whose tubular red and yellow petals flare like little trumpets. Both are hybrids of two prairie natives and grow to be about a foot tall.

¦ Hemerocallis. Day lilies come in thousands of varieties; there is a color, size and shape to suit every gardener. Burns calls them an old standby. Planting early, mid- and late-season bloomers along with ever-blooming varieties makes it possible to have flowering day lilies all season long. Anderson recommends ever-bloomers such as lemon yellow ‘Happy Returns’, deep pink ‘Rosy Returns’, glittering ‘Apricot Sparkles’, or pastel ‘Always Pink’. Day lilies, especially the older varieties, will tolerate poor soil and dry conditions.

¦ Perovskia atriplicifolia. Russian sage has airy, soft-gray foliage that provides a great background for other drought-tolerant plants such as agastache, rudbeckia and penstemon. Often called the backbone of the summer garden, Russian sage’s long branches are covered with sprays of small blue flowers in mid- to latesummer. The plants can grow to be five feet tall, but become woody with age and will benefit from being cut back hard in the spring. For small spaces, try dwarf ‘Little Spire’, which grows to between eighteen and twenty-four inches tall; for dark blue flowers, look for ‘Blue Spires’; and for upright, finely cut foliage and light blue flowers, check out ‘Filigran’.

¦ Rudbeckia hirta. Native to the Midwest, black-eyed Susans have naturalized across the United States and Canada. They bear yellow flowers with brown centers atop two- to four-foottall, wiry stems. Tireless performers, black-eyed Susans bloom profusely for the whole summer into the fall, even under the most adverse conditions. Although the plants are short-lived as perennials, they self-seed readily. Look for R. fulgida ‘Goldsturm’ for long-blooming, large flowers.

¦ Solidago. Goldenrod is often blamed for hay fever symptoms but actually the pollen is too heavy to be airborne. An easy-to-grow native plant, it blooms late in the season when the garden could use a splash of gold, pairing nicely with purple coneflowers. For a spectacular show, look for S. rugosa ‘Fireworks’, which has arching branches covered with yellow flowers, or dwarf S. sphacelata ‘Golden Fleece’, which grows to only fifteen inches tall but still blooms profusely.

Other Do’s and Don’ts

Lots of other perennials—such as rose campion, evening primrose, penstemon, chicks, and other stonecrops, are all good choices. No matter how hot and dry it gets this summer, you can have a gorgeous garden that is water thrifty and easy to maintain by using plants that are naturally adapted to hot, dry conditions.

Identifying Plants for Dry Conditions

A tip for easily spotting a drought-tolerant plant is to look at its leaves for one of the following characteristics:

¦ Thick leaves that help insulate the plant, keeping it cooler.
¦ Small, narrow or needlelike leaves, which have less surface area for water evaporation.
¦ White, silver or gray-green leaves to reflect light and heat.
¦ Waxy leaves that are slow to transpire moisture to the dry air.
¦ Fuzzy leaves to reduce the effect of drying winds and hold moisture near the leaf.