When people ask me "why a rock garden" I can think of no better answer than to say "it's the best way to grow trumpet gentians (Gentiana acaulis)". There are a cluster of gentians that are found from the Pyrenees in the west to the Balkans in the east that resemble one another closely, and are often subsumed by the single epithet: these variations (G. angustifolia, G. alpina, G. dinarica to name a few) do vary significantly in their geographical distribution, ecology and detailed morphology--but in bloom they are very similar to one another. I had large clumps of a half dozen subspecies growing in my Boulder Garden thirty years ago. I had these divided into hundreds of pieces and established in pots, and set most of these into the Rock Alpine Garden where almost all of them perished over the next two years (I planted them in too hungry and lean of soils: they like rich loam. A lesson I learned expensively.) There is a sort of intermediate beast that has been cultivated for at least 100 years and is generally easier and more floriferous than the wild forms in the garden. That is what we now have growing mostly in Denver: it is extremely easily grown in good loam, and very accommodating.
One enchanted afternoon in late June, 1986 I got on the ski lift in Pontresina, Switzerland with Ed Connors (who was chairman of the board of Denver Botanic Gardens about that time): we wafted above countless acres of Alpine tundra studded with countless millions of this dazzling gentian in full bloom amid mats of alpine azalea (Loiseleuria procumbens) and a hundred other alpine treasures. It was one of those golden afternoons one never forgets: when we got to the top of the mountain, Ed and I opted to walk back down through the throngs of sapphire trumpets: I was drunk with color and happiness that day. Each year as my colonies of trumpet gentians blossom, it seems the magic of the Alps returns in miniature to my own garden: each year there seem to be a few more of them, and they can bloom from mid-April almost to June with random flowers appearing in summer and autumn.
That blue of blues may be a challenge to photograph, but digital cameras seem to capture it pretty well. It's hard to believe in a brief four months I will be leaning over it once again and drinking in its royal blue.