In the Garden

heat lovers

The trick to nurturing a desert-friendly garden is to pick plants that are born to bake, create shady spots for the less hardy, and irrigate them—just enough and no more!

By Judith Phillips
Photography by Charles Mann

This article first appeared in Summer 2008 Su Casa

See our web-exclusive plant list at the end of this article.

Summer possesses restorative qualities. We spend long days outdoors energized in the cool, clear mornings, pass languid afternoons under the canopy of leafy branches, and recover momentum as the western horizon becomes streaked with grenadine and gold. Summer is the time for throwing open the garden gates to friends and neighbors, relaxing over food and drink, and sharing peaches or figs fresh from the tree and tomatoes still warm from the sun.

But the living is easy in the summertime only if the plants in your garden can take the heat. Rooted in place, they have no respite of air-conditioned spaces to retire to: if they can’t cope in the spot they find themselves, their only recourse is to throw out their seeds and hope that a few of them find a better venue in which to prosper. Fortunate plants find themselves in the hands of gardeners who’ve made wise decisions when putting their gardens together. They’ve given the heat-lovers center stage around walls and paving that reflect heat when summer turns cooking hot, and they’ve tucked the plants that need relief into the cooler shaded niches where they can lapse into a quiet lassitude until the shorter days of autumn revive their will to live.

The list of plants that bloom in spring and early summer is long and colorful, but once the daytime temperatures routinely hover in the mid-90s, the party winds down, leaving only the real heat-lovers to carry on, and a garden without them loses focus in summer. The stars of the season are either Southwestern desert natives or émigrés from the Mediterranean and similar hot, dry climates where plants are born to bake. Desert willow, our most heat- and drought-loving native tree, can be found in arroyos at or below 5,500 feet in elevation throughout central and southern New Mexico, where it thrives on occasional flooding from summer thunderstorms. In gardens it will bloom long and most intensely when the summer is hottest. Resisting the impulse to expend energy by setting seeds when temperatures soar, desert willow continues to flower strongly through the summer, much to the delight of hummingbirds and orioles who take turns sipping nectar while the sun burns brightly.

Chaste tree is native to the washes of Andalusia, where it benefits from storm runoff like desert willow does in New Mexico. The blue-purple flower spikes of chaste tree are rich in nectar sought by butterflies. Both desert willow and chaste tree are easily sculpted into beautiful garden specimens that offer light shade and fragrance through the heat of summer. Fig and pomegranate are also Mediterranean natives with a long history of cultivation for their tasty fruits. Both need to bask in the heat of the warmest microclimates in Albuquerque to be their most productive. In addition to their food value, figs’ beautiful bold foliage and stout branch structure offer screening and architectural presence while pomegranate flowers’ saturated scarlet color demands attention even at a distance.

Rose of Sharon has long been a garden staple even in places much colder and wetter than New Mexico, primarily because of its adaptability and consistent show of flowers through the hottest summer months. When bestowing its botanical name, Carolus Linnaeus assumed it was native to Syria, perhaps in part because of its remarkable heat tolerance, but the plant is now thought to have originated in China, its true roots somewhere along the Silk Road. In modern times, rose of Sharon has been bred for a wide range of color. Its fluted flowers run the spectrum from blue-mauve to wine and deep rose pinks, salmon to white and bicolor mixes. In colder climates it may stay a shrubby 6 to 8 feet in height, but happy for the long, hot growing season in much of New Mexico, it tops out at 12 feet or taller. Scholar tree is also native to arid regions of China and keeps its cool while keeping us cool in western cities from Denver, Colorado, to Albuquerque and Socorro, New Mexico. Its dark green divided leaves create a dappled shade canopy eventually 30 feet or taller arching almost as wide. Honey-scented white flowers open in midsummer followed by small flat greenish-yellow seed pods that reflect its kinship to our native mesquite.

Among the shrubs that wash the summer in cool shades of blue are two Chihuahuan Desert natives that bloom in response to summer rain or the occasional deep soaking when clouds fail to deliver. ‘Rio Bravo’ Texas sage is a larger shrub, growing four feet tall and wide, densely covered with small soft green leaves and bursting with blue-purple tubular flowers that hummingbirds love. Native to the Chisos Mountains at Big Bend, Texas, sages were commonly called barometer bush by early ranchers as they seem to respond to every rain with a flush of blossoms. Mexican blue sage has small evergray leaves and China blue flowers on silver stems. The plants are mounded in form; the slender flower-tipped stems are two feet tall and plants root-sprout at the base, creating cushions two to three feet wide. From a distance Mexican blue sage resembles lavender, a summer flowering Mediterranean plant that deserves its place in the sun not only for its purple flowers, but also for the invigorating aroma released when its foliage is brushed against. Mexican blue sage leaves are wider, rounded, and even more silver than most lavender, its flowers a deeper blue, and it grows well in heavier clay soils while lavender prefers well-drained sand or decomposed granite.

Still another blue-purple summer bloomer, dwarf butterfly bush responds to deep watering every few weeks in summer by producing sprays of blue or purple flowers throughout the season. As its name suggests, it is smaller-stemmed and more refined in texture compared with common butterfly bushes; it thrives with less water and needs less pruning to keep in shape, and butterflies find it irresistible.

You’ll find a rainbow of heat-loving summer-blooming perennials. Like desert willow, bush penstemon grows wild in arroyos that may flood one year but not another. This is also a fairly common roadside wildflower growing in the swales that catch moisture running off of pavement. In flood years, arroyo plants are often buried in the sand and emerge to bloom soon afterward. In drier years they rely on deep roots and very water-conservative small leaves to support their summer blooming habit. To make the most of what little water is available in extremely dry years, they may bloom heavily in early summer and give a repeat performance in early September. In gardens, they continue to produce spikes of pale-pink tubular flowers with deep-wine-colored throats if given a monthly deep soaking in lieu of rain.

Hummingbird mints are native at middle elevations—4,500 to 7,000 feet—in the southern mountains. One of the most heat-loving and brilliantly colorful species, bubblegum mint earns its name for its sweet-scented screaming-pink flower spikes topping strongly upright stems that grow at least 30 inches tall. Another is licorice mint, with coral blossoms on lax two-foot stems, a softer profile, and a refreshing anise-licorice-root-beer fragrance. Unlike the water- and shade-loving cover-the-neighborhood roaming ways of peppermint and its ilk, Agastache are mints that grow up from a central crown and rarely self-sow, so they stay put and bring hummingbirds to visit. Hummingbird trumpets, with their dazzling red-orange flowers, are another group of summer-blooming perennials that attract the frenzied little birds. Hummingbird trumpets are mounded plants that may grow two feet high and wide or sprawl twice the width depending on the available moisture. Both hummingbird mints and hummingbird trumpets are slow to green up in spring, waiting until the soil is warm before they start their garden year.

Smaller in scale but no less potent in color are yellow-flowering desert zinnia and the rose-pink prairie succulent flameflower. Used separately or combined along the edges of paths, between flagstones or boulders, these ground-hugging plants continue a strong show of color all summer, even when eggs could fry on the sidewalk. Desert zinnia grows tufts of short soft stems barely six inches high that root-sprout and gradually become a continuous pale-green grasslike carpet. Once desert zinnia begins to bloom, the one-inch-diameter bright-yellow flowers obscure the foliage completely. Old flowers dry and break off their stems as new flowers are forming, sometimes creating a mulch of dried flowers a few inches deep if they aren’t cleared away. Flameflower also grows tufts of slender succulent leaves that tell of its close kinship to the garden annual moss rose. It spreads by self-sowing readily but is never weedy as the individual plants are small, charming as they fill in nooks and crannies, and easily removed if they show up where they aren’t wanted. The paradoxical flameflower offers a wispy persona of dainty rose-pink flowers floating eight inches above the leaves on wiry gold stems accompanied by an iron-tough will to live long and prosper in the hottest, sunniest spaces.

Plants that need to bask in the heat to garner the energy for blooming and producing their fruit and seed also need to be very efficient in their use of water, and while they do prefer some irrigation to work their garden magic, they will suffer, grow more slowly, and be prone to root rot if kept too wet. The trick to successful xeric gardening is to achieve the best result with the least amount of water. In most cases, watering to moisten the soil to a depth of 30 inches twice a month during the growing season is enough to keep the larger plants healthy and in bloom once they have rooted extensively. More shallowly rooted plants such as the zinnia and flameflower may be watered every week to 10 days to a depth of 12 inches to keep them in bloom, monthly when not flowering.

A widely acknowledged expert and author on regionally appropriate gardening, Judith Phillips has designed more than 900 residential gardens, collaborates on design teams for public landscape projects, and teaches a native and xeric plant class at the University of New Mexico.

 

Natural selections

Natural selections: heat-loving plants
Bubblegum mint (Agastache cana)
Bush penstemon (Penstemon ambiguus)
Chaste tree (Vitex agnus-castus)
Desert willow (Chilopsis linearis)
Desert zinnia (Zinnia grandiflora)
Dwarf butterflybush (Buddleia davidii nanhoensis)
Fig (Ficus carica)
Flameflower (Talinum calicynum)
Hummingbird trumpets (Epilobium syn. Zauschneria species)
Lavender (Lavandula x intermedia)
Licorice mint (Agastache rupestris)
Mexican blue sage (Salvia chamaedryoides)
Pomegranate (Punica granatum)
Prairie zinnia (Zinnia grandflora)
‘Rio Bravo’ Texas sage (Leucophyllum langmaniae)
Rose of Sharon (Hibiscus syriacus)
Scholar tree (Styphnolobium japonicum)