Choosing a palette of plants that thrive despite climatic extremes
BY LAUREN SPRINGER
AFTER GARDENING IN COLORADO for a dozen years, I thought I could handle any climatic insult. There is a reason why meteorologists consider this state a mecca; as the local adage goes, if you don’t like the weather, wait five minutes. In the relatively short time I’ve lived here, I’ve endured several summers with a record-breaking number of days above 90°F, winds well over 100 miles per hour, two winters that saw the mercury dip to 30 below, three garden-wrecking hailstorms, April and October snows of over three feet each, and, on one Halloween, a temperature drop of 70° in 24 hours.
Yet nothing prepared me for the most recent weather patterns, or for the peculiarities of my present site. In 1999, 14 inches of rain fell between April and June, more than we often see in an entire year. Many dryland plants—bearded iris, penstemon, buckwheat—bloomed like never before and then rotted. The courtyard garden, where I planted more traditional, irrigated fare, was under an inch of water for well over a month. Algae covered the flagstone path to the house, as the hillside above seeped water until mid-July. The creek in the canyon washed out the road and two bridges, stranding several families. Cliffs wept waterfalls for weeks; sheets of wildflowers burst from the surreally green grassland.
Then it all dried up. For two and a half years and running, northern Colorado has been in a severe drought. On my site we measured nine inches of moisture in 2000, and just shy of seven inches in 2001. Our once-productive well ran dry the past two summers, a misery incomprehensible to suburbanites and city dwellers who can usually run for the hose. In the once-moist courtyard, I have watched most of the trees, shrubs, and perennials succumb. Many bulb species have fared well, which is to be expected, since their life cycle evolved to deal with such extremes. Rising from the ashes of meteorological devastation is another group of plants that thrived in the muck of the flood and have mastered the parched clay—a category of plants never found in gardening books. I have learned about them the hard way, by trial and error, and am now filling the many gaps with more of these adaptable grasses and perennials. After all the wheelbarrows of dead and dying plants have been dragged from the courtyard, there’s still hope. A new garden is growing, soon to be a resplendent steppe planting of the toughest of the tough.
Although this kind of gardening is new to me, and there is very little information available, certain patterns are already emerging. Most obvious is their provenance—mainly prairie and steppe regions that experience intense seasonal variation in moisture, from deluge to drought, on a regular basis. Also, plants adapted to clay soils seem better able to thrive in both extremes, perhaps because a wet clay soil is a far cry from a wet sandy soil, which is rarely if ever truly saturated and anaerobic. A closer look also reveals that certain genera and even families have an inborn adaptability. Eryngium, Paeonia, and Euphorbia are winners, and the legumes are well represented by Baptisia, Dalea, and Thermopsis. Taproots and root systems that are sparse and/or slightly tuberous dominate among the survivors. In a number of instances, the more fibrous-rooted species within the same genus succumbed, while the deeply-probing, thicker rooted species survived; Nepeta sibirica and the centaureas are cases in point.
Also, when looking within a genus that is generally a moisture-tolerant one, the species that adapt to drought tend to be those with leathery and/or blue foliage. It should be emphasized that this is true only within genera that tolerate moisture—just having blue or leathery leaves does not qualify a plant as tolerant of both extremes; in fact, most drought-loving plants with these characteristics rotted during the wet period. But a look at the numerous Amsonia, Vernonia, Solidago, and Thalictrum species that were tried reveals that in all cases the surviving species has distinctively thicker, more leathery, or waxy leaves, often with a blue color.
PLANTS THAT CAN TOLERATE SEASONALLY
PERENNIALSAmsonia illustris (other bluestar species were severely stunted by drought) ? Baptisia australis, B. minor ? Centaurea macrocephala, C. orientalis (other species rotted) ? Cephalaria alpina ? Clematis integrifolia and its hybrids ? Dalea purpurea ? Delphinium grandiflorum, D. tatsienense ? Eryngium giganteum, E. planum, E. yuccifolium ? Euphorbia amygdaloides ‘Rubra’, E. epithymoides, E. palustris ? Hemerocallis ? Iris missouriensis, I. orientalis, I spuria (bearded irises rotted; Siberians were severely stunted by drought) ? Knautia macedonica ? Limonium gmelinii ? Nepeta sibirica ‘Souvenir d’Andre Chaudron’ (other nepetas rotted) ? Paeonia mlokose-witschii, P. obovata, P. tenuifolia, P. tenuifolia xlactiflora hybrids (other peonies suffered from drought) ? Parthenium integrifolium ? Patrinia scabiosifolia ? Potentilla atrosanguinea, P. nepalensis and their hybrids ? Ratibida pinnata ? Salvia forsskaolii, S. nemorosa, S. pratensis, S. verticillata ? Sedum telephium ‘Munstead Red’ (others rotted) ? Silphium laciniatum ? Solidago rigida (other goldenrods suffered or died from drought) ? Tanacetum parthenium ‘Aureum’ ? Thalictrum flavum subsp. glaucum ? Thermopsis fabacea ? Vernonia missurica (other ironweeds died from drought) ? Veronica longifolia ‘Blue Giant’ ? Veronicastrum sibiricum
GRASSES AND SEDGESAndropogon gerardii ? Calamagrostis xacutiflora ‘Karl Foerster’, C. brachytricha ? Carex grayi ? Panicum virgatum ? Schizachyrium scoparium ? Sesleria autumnalis, S. caerulea, S. heufleriana ? Sorghastrum nutans (not ‘Sioux Blue’-seed-grown Indian grass is more drought tolerant) ? Sporobolus heterolepis ? Stipa calamagrostis
First row: Iris spuria, Ratibida pinnata, Centaurea macrocephala, Thalictrum flavum subsp. glaucum, Tanacetum parthenium, Second row: Eryngium yuccifolium, Paeonia tenuifolia, Salvia verticillata ‘Purple Rain’, Clematis integrifolia, Potentilla atrosanguinea, Third row: Schizachyrium scoparium, Calamagrostis brachytricha, Sorghastrum nutans, Calamagrostis xacutiflora ‘Karl Foerster’, Sesleria autumnalis
FIRST ROW: ALEKSANDRA SZYWALA, SAXON HOLT. MICHAEL DAVIS, MARK TURNER. MICHAEL DAVIS. SECOND ROW: ROB CARDILLO. ALEKSANDRA SZYWALA. SAXON HOLT. ROB CARDILLO, LAUREN SPRINGER. THIRD ROW: DAVID CAVAGNARO. DAVID CAVAGNARO. DAVID CAVAGNARO. SAXON HOLT. SAXON HOLT
My hope is that most gardeners do not have to concern themselves with such conditions. As a friend once said upon visiting my stunning but challenging site and hearing my tale of woe, “For the good fortune of living in such beauty, you deserve your share of trials and tribulations.” There’s a reason so much of the West’s splendor is unspoiled—it is, for the most part, nonarable, untameable land in an unforgiving climate. The key to gardening here lies in utilizing native plants and those from similar parts of the world, a mantra that applies to gardeners everywhere if we are to create beautiful, thriving, ecologically intelligent gardens.
For sources of these plants, turn to page 92.
To learn about xeriscaping, visit www.hortmag.com/features.
Memoru shapes the gardener