These tiny jewels all start with “A” and sparkle in local rock gardens
By Panayoti Kelaidis
With the Flatirons peering over one’s shoulders, it’s hardly surprising that Boulder County has its share of rock gardeners.
Many of us love living in Colorado because of the proximity of the Rockies and their glorious alpine meadows. We dash up there whenever we can to explore them, but why not plant a few alpine beauties in our home landscapes?
Of course, many true alpines won’t grow at lower altitudes, but a surprising number can adapt to Front Range gardens. Large perennials and shrubs can smother home gardens with limited space, whereas small-scale plantings interspersed with rocks can open up the space and allow you to grow a greater variety of plants.
Home rock gardens can be very functional and low-maintenance, with compact ground covers that form evergreen mats alongside kaleidoscopes of alpine flowers that provide brilliant color.
Some of the plants listed here are true alpines from above tree line; others are small-scale plants that only look like they’re from higher heights, but are actually from rocky habitats lower down. All these “alpines” are available at local nurseries and from mail-order sources, and they’re durable in our regional gardens if given a rock garden setting with well-drained soil.
This plant is widespread in western Eurasia at all altitudes, and is very decorative and fragrant. It forms a low mound of wiry, evergreen foliage with a bright bluish-green color, and it’s a perfect mounding shrublet, up to a foot across and little more than half that tall. It’s covered with light pink or purple flowers for the better part of two months in spring and early summer, which transform into attractive, chartreuse seed heads in late summer and fall. The plant thrives in any kind of soil and even grows in non-watered gardens, so it’s high on my list of essential garden plants.
The plants in the genus Asperula are fantastic rock garden plants, and many, like this one, are bona-fide high alpines. Although I’ve grown this attractive plant for decades, it was only in 2015 I had a chance to see it in the wild, growing on the summit of Mount Ida near Troy (now Kaz Dag National Park) in Turkey, where it made helmet-like mounds of gorgeous pink blooms. It will be just as stunning in your garden!
In nature, the rosettes of this amazing, hardy ice plant are buried underground much of the year, with only the warty, lizardy leaf tips poking up. In early spring, these are studded with bright rose-pink flowers that glow in daylight but close at night. This is a steppe plant in nature, needing a sunny exposure and not too much water to thrive. This plant has produced many self-sown seedlings in the gravel pathway at the crevice garden in Arvada’s Apex Park.
This daisy is found in nature at high altitude in the Atlas Mountains of Morocco, but it grows as enthusiastically as a native in gardens here. A filigree rosette of dusty green leaves splays out a cartwheel of frilly stems studded with pure white daisies over an inch across. The blooms last much of spring and early summer, and I find the plant especially lovely at dawn and dusk, when the ray flowers close to reveal a bright red undersurface. I plant it between paving stones, although it grows just as happily in sunny rock gardens, where it will seed around modestly.
Not everyone has a sunny spot for a rock garden. Not to worry—in nature, many rocky hillsides are shaded by trees or face north and still harbor a variety of beautiful wildflowers. Anemones often do best with some shade. I’ve found this unusual bright yellow woodland plant to be vigorous and very showy. It makes mats of attractive foliage 3- to 4-inches tall that are speckled with shiny yellow flowers that do suggest buttercups. It blooms from mid-to-late spring and dies back in summer, so combine it with miniature hostas or ferns in the shadier space where you plant it.
Rock cresses have graced walls and rock gardens from time immemorial. This rock cress is half the size of the common rock cresses, and looks especially in scale and attractive in rock gardens. The rock garden my brother-in-law, Allan Taylor, built at my parents’ Boulder home had masses of these, with their gorgeous mats of starfish rosettes obscured under electric lilac, blue or purple flowers for months in spring and early summer. This is a bone-fide alpine from Mount Olympus, where I saw it growing above tree line.
7Aster ericoides ‘Snow Flurry’
Heath aster is a tall meadow plant found in most states of the continental U.S. The typical aster can grow a foot tall or more and spread rather too enthusiastically for most gardeners. But the snow flurry is a miniature weeping selection that’s a fantastic element in a sunny rock garden, spreading to a foot or so across and only a few inches tall. The cheery white blossoms make a perfect miniature avalanche in late summer, draping over rocks and covering spots where bulbs bloomed earlier in spring. I have three of these in my garden and I’m contemplating adding more.
Not many South American plants appear in local gardens, but this striking cousin to the carrot has been successfully grown here for decades. It forms a dense mound of rubbery rosettes that give Astroturf a run for its money in compactness, toughness and resilience. The yellow flowers are showy for much of the early season, and often produce decorative seedpods. This mat-like plant can spread to cover many feet in time, but it can be easily controlled and kept in scale, and friends are most often delighted to receive divisions.
The Garden that Rocked Boulder
In the 20th century, Boulder’s most beautiful rock garden was unquestionably that of the late professor T. Paul Maslin, who taught biology at CU. His garden consisted of monumental conglomerate boulders of the Fountain Formation—the Flatirons, basically—excavated from the foundation of the home he built and arranged (with the help of a skid loader) by his artistic eye.
Maslin filled his garden with a vast assortment of floral treasures, few of which had been grown elsewhere in the state, including a tremendous range of alpine plants. I walked past the Maslin garden daily as a child, since it was on my route to school and back. I would peer through the carport, where the magical vista beyond beckoned. That view, and the bold rockwork, became a sort of obsession for me. I would watch the transformations through the season, and take note of every flower, every change. It’s no accident that when I grew up, Maslin and I became best friends. We even founded the local chapter of the North American Rock Garden Society together in 1976.
The Garden that Stocked Boulder
Over a century ago, Darwin Andrews established Rockmount Nursery roughly where the National Institute of Standards and Technology in Boulder stands now. Rockmount became the region’s premier nursery and a mail-order source for native wildflowers, alpine plants and seeds from around the globe. In the classic book “The English Rock Garden” by Reginald Farrer (the “patron saint” of rock gardens), the author acknowledges Andrews for supplying him with Rocky Mountain natives. Growing up in Boulder, I perused a vintage copy of this book at CU’s Norlin Library. Inside the front cover, Farrer had autographed the copy for Andrews. This year represents the centenary of the book’s publication, while 2020 marks the centenary of Reginald Farrer’s death on the alpine heights of Burma while on a plant expedition. What better way to honor these anniversaries than to build a rock garden?