Why the Rocky Mountains are a treasure trove for English gardeners

Around 3am, during my first night up in Colorado’s Rocky Mountains, I woke with the camper’s urge to pee and was forced from the comfort of my small tent. Fumbling with my shoes, trying not to wake my friend in the adjacent tent, I pushed out into the cool mountain air, and stood for a moment while my brain rebooted.

A bright moon and a blanket of stars lit the scene, gilding the surfaces of lichen-smattered granite boulders and embossing great ponderosa pines. In the distance, the lumpy silhouette of Longs Peak. At the base of the trees closest glimmered a pool of wildflowers that, in this fleeting nocturnal moment, made my heart sing: upright blue penstemon, pink geranium, creamy heuchera and a swathe of pincushion buckwheat that appeared almost sulphurous in the moonlight.

I was drawn to them like a moth (forgetting, momentarily, the potential risk of bears –the camp ranger had warned of their presence here the previous night). Together, they were just an ounce of Colorado’s rich botanical offering. This all boded well; tomorrow we would go looking for the mountain columbine (Aquilegia caerulea) – Colorado’s state flower, and the wild westerner that has long been a staple of British gardens.

I have been steadily making my way through the contiguous United States throughout much of the past decade (Covid disruptions aside), clocking up around two thirds of the “Lower 48”. What fascinates me always is the astonishing array of America’s indigenous plantlife, so much of which has been introduced and contributed to British horticulture over the years.

Last summer, I ticked Colorado off the list: that immense rectangle positioned a little west of centre, home to the wild forebears of many cultivated garden treasures (asters, penstemons, coreopsis, gaillardia, rudbeckia, et al). And I can wholeheartedly say that, where magnificent landscapes and exhilarating flora are concerned, the “Centennial State” is unequalled.

As the regional anthem declares: “Tis the land where the columbines grow, overlooking the plains far below”, and no flower is quite so exquisite as the wild Colorado columbine. To see this cottage garden favourite growing wild in the rugged Rockies had long been on my botanical bucket list.

Arriving in Denver, you sense why Colorado is a Mecca for the outdoorsy type. For all the city’s urban sprawl, outdoor recreation stores and outfitters abound, reinforcing the state’s reputation as number one for hiking culture. The conservation of indigenous Rocky Mountain flora – a locally valued asset – also takes centre stage at the popular Denver Botanic Gardens.

So during a stay in the “Mile High City” one acclimatises to the altitude, enjoys a craft beer and purchases backpack essentials for exploring the surrounding scenery. At least this is what my friend and I did, the night before camping in Larimer County’s Hermit Park, a stretch of recreation ground in the eastern portion of the Rockies’ Front Range, characterised by sweeping vistas and floral profusion. Before we had even unpacked the tentpoles I was revelling in a drift of lupin-like purple locoweed and iconic American blanket flower, or Gaillardia aristata.

Sprawling wilderness

We chose Hermit Park for its comparative quietness: a less populated summer camping spot within reach of both Rocky Mountain National Park (415 square miles of spectacular mountain-scape) and the lofty town of Estes Park. In the late 19th century, a few years after Colorado’s 1850s gold rush – though just prior to its admission to the Union – the British author-explorer Isabella Bird visited Estes Park, describing it in her published diary, A Lady’s Life in the Rocky Mountains, as “perfection”. She enthused: “The scenery is the most glorious I have ever seen ... there is health in every breath of air.”

In the weeks prior to my trip I pored over Bird’s account of pre-statehood Colorado; of traversing its sagebrush prairie and scaling the dizzying Longs Peak. Alongside encounters with bucking broncos and grizzly bears, Bird paints a picture of a terrain as varied as it is beautiful: its reddening peaks and lily-covered lakes; its rolling plains like the waves of a placid sea. What surprised me when visiting was that, bar the ubiquitous strip mall, so much of the state remains similar to these century-old visions of variable countryside.

At Garden of the Gods park I wandered below martian-red rocks as the horizon vanished along Route 285 into unending grassland; I followed wooded tracks and alpine tundra paths and, at Salida, sat beneath giant cottonwoods, my legs cooling in the roaring Arkansas River. Throughout, divergent flora echoed the changing landscape: arid yucca and prickly poppy gave way to mountain monkshood and cool blue flax.

Sublime sights

We encountered the greatest range of plants in the high meadows of Crested Butte, an unimaginably beautiful place where a wildflower festival (crestedbuttewildflowerfestival.org) is held each year after the snow has melted. But it was at the fringes of Rocky Mountain National Park, following the crystal clear Tonahutu River through a forest valley regenerating after a recent wildfire, that, with much excitement, I encountered my columbines.

Hiking with a guide, my friend and I had paused at the sudden and sublime sight of a young moose crossing the path ahead. Concerned that a bullish parent could also be close by, our guide had us wait a while in the clearing. I happily obliged: seeds germinated in the wake of the fire had produced a valley positively shimmering in wildflowers: hairbells, asters, arrowleaf, bedstraw and, appearing there in the grass beside me, the unmistakable blue of the Colorado columbine.

Widely considered the most beautiful of all aquilegias, the remarkable delicacy of Aquilegia caerulea comes from its wispy rear spurs, which project the large bi-coloured bloom like a shooting star. It is a flower utterly redolent of its surroundings: the petals white like the snowcapped mountains; the outer sepals, pure “caerulean” sky blue. I could see immediately how it earned the status of state flower and why, in cultivation, it has gained an RHS Award of Garden Merit. Rough living in the Rockies has instilled a natural tolerance for sun, shade, chill and wind: a tough mountaineer we should be humbled to have grace our gardens.

Five Rocky Mountain perennials to try in the garden

Blue columbine

Aquilegia caerulea is best sown from seed throughout summer and overwintered to produce a short-lived perennial. It will take to a range of sites and soils, though prefers a moist but free-draining environment. Remove flower stems after blooming to prolong the life of the plant.

Penstemon

I should have known that while out looking for Colorado columbines, penstemons would prove a distraction. A great number occupy this intermountain region, from the vibrant, candy-blue P. strictus and P. virens to the fiery red P. barbatus that line the roadsides.

My favourite, however, was P. whippleanus: a dwarf plum-purple seen all over Rocky Mountain National Park. Try the cultivar ‘Chocolate Drop’.

Veratrum

Known as ‘corn lily’, Veratrum californicum is a tall, verbascum-like perennial with attractively large, pleated foliage. It is at home in a range of habitats: I stumbled upon clumps of these impressive cream-white flowers in the high meadows around Crested Butte. Note: toxic if eaten.

Aster (Symphyotrichum)

Of all flower types abundant in the Rockies, you cannot escape the composites: daisies in every colour and shape. Here and there – particularly in open meadows – I came across low mounds of floriferous aster, the pretty American daisies reclassified as Symphyotrichum. A popular cultivar is S. laeve ‘Calliope’, which has dark green foliage and cornflower-purple flowers.

Thermopsis

At the Garden Museum’s most recent plant fair, I purchased a curious deep yellow golden pea (Thermopsis montana). Then new to me, it was common in the Rockies, brightening riversides and woodland glades. Somewhere between a lupin and a baptisia, it is an excellent rhizomatous perennial for semi shade.

For further information, visit colorado.com