- Lee Recca
Report from the Steppe Symposium
Rooted in Stone: A Geologist Connects with Gardeners
By Lee Recca:
Dr. Bob Raynolds kicked off the Global Steppe Symposium by taking us into space to look at the Colorado River Basin and its spectacular geologic features. Then, he brought us down to the garden level to ask us to find solutions and adaptations that will allow people to mitigate climate change, accept climate change, and model new ways of living and gardening.
Raynolds is an eminent geologist with ties to the Colorado School of Mines and the Denver Museum of Nature and Science. His overview of Colorado’s rich geologic history and its rock and mineral layers was dazzling but much of his talk revolved around water. Water not only reveals and interrelates with the mountains, plains and canyons of Colorado but also outlines its most impacted places, carving a series of question marks in its meandering or tumultuous journey to the sea.
Colorado is a unique place in terms of water. It is a “headwaters state” meaning our mountains make the water on which 40 million people depend, including five million Coloradoans. Why is this important to Front Range gardeners? After all, 80 percent of the water in the Colorado River flows west. But Dr. Raynolds pointed out that half of Denver’s water comes from the Colorado River. A majority of that water is used to grow and maintain “green grass,” he said. Green grass in yards, parks, golf courses and other recreational places is not sustainable, he warned. He implored the audience of rock gardeners, teachers and landscape professionals to help people stop living as if they're “in New Jersey.” The “Garden State” boasts 45 inches of average annual rainfall, while Denver averages about 12 inches.
Another area of concern addressed by Dr. Raynolds is agriculture. All of the good efforts of homeowners and gardeners won’t make enough difference, because a whopping 87 percent of water usage in the state goes to agriculture. Much of that, he said, goes to raising fodder for cattle: alfalfa, corn and hay. His outlook was hopeful that, as people eat less beef, this amount will decrease. His conclusion, seconded by audience remarks, was that it’s not happening fast enough.
Colorado’s Soils and the Plants that Love Them
Whatever you call it – a meadow, a prairie, a clearing, a glade – it’s the space that has recently caught the eye and claimed the heart of many a plantsperson and landscaper. That includes the Denver Botanic Gardens duo of Michael Bone and Kevin Williams.
Building on the opening talk, “Rooted in Stone”, at the Global Steppe Symposium, Williams and Bone sought to “bring the wild home” by detailing which plants, both native and introduced, could thrive in each of the five main ecoregions of the state.
The flat to rolling plains found from Denver to Fort Collins and east to Strasburg are Steppe, welcoming to native plants such as the Baby Blue variety of Rabbitbrush, Winterfat, and the Pawnee Buttes Sand Cherry (Prunus besseyi). The deeper sand plains soils are good hosts for natives such as Cowboy’s Delight (Sphaeralcea coccinea), Mexican Hat (Ratibida columnifera), Prairie Sweet Sand Verbena (Abronia fragrans), and Winecups (Callirhoe).
There are gravelly sandstone and loam combinations of soils found in Colorado Springs east to Yoder and Matheson with a different selection of plants. Further south, a crystalline dust forms soils from Westcliffe into the parklands and canyonlands. This mineral-rich soil fosters plants such as Lambert’s Loco (Oxytropis lambertii), Erigeron, Columbine, and Ball Cactus.
Did you know that Green Mountain in the Denver suburbs is an alluvial fan? Sand, gravel, and silt flowed from the mountains onto the plain and built up over time. Williams and Bone recommended native plants such as Corydalis, Evening-primrose (Oenothera), and Wood Lily (Lilum philadelphicum) that grow well in alluvium.
Foxtail lilies (Eremurus sp.) appeared on the list of introduced plants that do well in Colorado soils and Bone suggested a native plant, Golden Princes' Plume (Stanleya pinnata), which could be considered “America’s answer to Eremurus.” As the icing on the cake, the researchers threw in a sizeable list of plants that thrive in most ecoregions of Colorado.
To develop the plant lists, Bone and Williams used an online collection of herbaria called SEINet and EPA-developed maps of Colorado’s ecoregions. Their extensive research was very convincing so that, as DBG Senior Director Panayoti Kelaidis says, “If you can’t be with the soil you love, love the soil you’re with.”
EPA ecoregions:
SEINet Colorado:
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