I can remember a time, not too many decades ago, when twinspurs were virtually unknown in gardens. Although they’re not quite in the top tier of bedding plants, twinspurs have nevertheless become staples in hanging basket and container gardens across North America. Adventurous gardeners will even use them as fillers in perennial borders, or in special bedding schemes where their unusual colors and long season of bloom are welcome. In California, perhaps, or other mild weather regions, some of the common cultivars may persist a few years; for most of us, however, the twinspurs are annuals. That is, except for one that possesses an unusual degree of cold hardiness and stamina. This piece means to introduce Coral Canyon®twinspur to a wider audience.
Twinspurs are so named because each flower has two hook-like petal segments projecting backward, with nectaries containing an oil gathered by specialized bees. They have co-evolved with these Rediviva bees, and rarely produce seed naturally in the garden. There nearly 70 species in the genus found across South Africa, many found in the Drakensberg Mountains where winters are snowy and cold, so some possess a measure of winter hardiness in America. The twinspurs distinguish the genus from closely related Nemesia and Alonsoa.
Name: Diascia integerrima Coral Canyon®
Common name: Coral Canyon® twinspur
Hardiness: Zones 4b to 10
Mature height: 12 inches to 18 inches
Mature spread: 2 feet or more in 2 to 3 years
Classification: Herbaceous, dedicuous perennial
Landscape use: Perennial borders, bedding plant schemes, containers or in a rock garden
Ornamental characteristics: Provides a mass of color for months — much as an annual would, but it is reliably perennial in well-drained sites
I had become so enamored of the group that I purchased every clone I could get – mostly from renowned Heronswood Nursery, which imported a seemingly endless variety of species and hybrids from England where the genus was wildly popular. Many came ultimately from Royal Botanic Gardens at Edinburgh, where Olive Hilliard and Brian Burtt were collecting them in the wild and studying the genus at that garden. Nowadays, dozens of selections have been released in Europe, America and Australia: They’re hot!
I first obtained the typical Diascia integerrima in 1991 from Canyon Creek Nursery in California. It became an immediate sensation when I planted it in the Rock Alpine Garden at the Denver Botanic Gardens, forming billowing mounds of soft pink all summer on meter-tall, somewhat flopping stems. It came back vigorously the next year – and then a third One day, Kelly Grummons, one of the greatest nurserymen in the area, was strolling through the garden with me: When he saw these clumps he said, wistfully, that if it only grew more compactly it would be a winner.
A few months after Kelly expressed this wish, I found myself on the wonderful alpine slopes of the Drakensberg Mountains. Here and there I saw a very small twinspur that resembled the massive clumps I’d seen on Sani Pass, for instance, only these were less than a foot tall. I found a single capsule of seed on these that appeared to be nearly ripe, and from that capsule ultimately derives the plant we now call Coral Canyon®! Because the cultivar comes from the wild, it could not be patented. But the name for it could and was trademarked, hence the “registered” symbol following its name. This guarantees that this clone is indeed Plant Select’s consistent offering.
It’s hard to believe the rather frail wildflower produces such a vigorous mound of flowers in cultivation: Coral Canyon® can spread to several feet across in rich garden soil, the flower stems forming a billowing mound up to 18 inches if well-watered and fertilized. The delicate foliage can be completely obscured by the flowers from late April some years – and it is still in full bloom here at Denver Botanic Gardens on October 1 as I write this.
The name Coral Canyon® alludes to the buff pink color one sees so often in the Southwest – in the Canyonlands, on the Coral Pink sand dunes, and often in our Western dawns. This color combines well with bright blues, lavenders and even yellows, colors that characterize long-blooming Xeriscape perennials. I especially love to see it alongside lavender, which blooms for almost as long and likes the same sunny spots.
Culturally, it thrives in much the same culture one would give any twinspur: a porous, well-drained garden soil or container. It seems to do well with more sun and can tolerate greater drought and less fluffy soils than the commonly offered bedding plant twinspurs. The real difference shows up the year following, when most hybrids will have petered out, but Coral Canyon® comes roaring back yet again to grow and bloom with special vigor! They are superb in mass plantings, or as single specimens. Coral Canyon® grows well in containers and baskets, although not quite as winter hardy if left outdoors in pots in colder climates, obviously.
The many propagators in the Plant Select program have offered this in all manner of plug trays and pots for nearly 20 years now. I am nonetheless surprised that I so rarely see this even in the Denver area where we first cultivated the clone. David Salman has told me that he thinks this is the finest introduction from South Africa I’ve ever made – and considering I’ve brought back most of the Delosperma species and a bevy of Kniphofia and many other gems, that’s high praise indeed!