by Kristl Walek
If you have sought out daisies suitable for the rock garden,
you have undoubtedly tried the ubiquitous (and not particularly small)
Aster alpinus. Then there are the worthwhile mounding and rock-hugging
species of Erigeron, as well as members of the genus Townsendia. The
latter are small and beautiful as a clan, but generally monocarpic.
T. parryi is the only species that has persisted through self-sowing
in my garden.
One could name western daisies. There are choice forms
of Heterotheca, such as H. jonesii, perhaps the best small
yellow daisy for the rock garden. It has fantastic silver foliage and
blooms all season. I have also experimented with Hymenoxys but many
of the choice endemics of the American Rockies do poorly or are short-lived
in my eastern North-American garden.
is why it was such a pleasant surprise to find a beautiful, small, western
daisy that is so happy here. Machaeranthera coloradensis (formerly
Aster coloradoensis) is considered by some to be the finest
American aster. It is at home in Colorado and Wyoming growing in sparsely
populated patches on gravelly or rocky slopes in full sun. It has recently
taken on threatened status in both states.
The plant is a small gem 4-5cm (1.6 – 2.0”)
tall to 15cm (5.9”) wide, forming lovely open mats of toothed,
silvery foliage. Comparatively large, luminous bright pink flowers are
produced on short stems all season. I have tried it in the rock garden,
sand bed and in scree; it has been happy everywhere.
While it is a bonus to have long-blooming plants in the
garden generally, we do not have as many choices among rock plants.
The Colorado Tansy-Aster will begin flowering soon after the rush of
the spring alpines finishes and continues blooming until fall. Although
I would surely welcome it, there has been no self-sowing in my garden.
However, it is easy to collect the fluffy seed once ripe and to sow
it that winter to increase one’s collection. It germinates easily
without needing any cold treatment.