Snow-in-Summer

What’s still green: Arborvitae, juniper and other evergreens, Apache plume, fewer rose stems, cholla, prickly pear, yuccas, Japanese honeysuckle; snow still covers grape hyacinth, St. John’s wort, vinca, beardtongues, coral bells, rock rose, sea pink, pink and yellow evening primroses, purple aster, cheat grass, bases of needle and June grasses.

What’s grey, blue-grey or grey-green: Piñon, pinks, snow-in-summer, saltbush, winterfat.

What’s yellow: Weeping willow branches.

What’s blooming inside: Christmas cactus, bougainvillea, aptenia, asparagus fern; rochea and Christmas cactus leaves tinged with red.

Animal sightings: Rabbit in drive.

Weather: Veneer of new snow when I awoke Thursday morning.

Weekly update: The best thing about snow-in-summer is that the grey leaves are always there. Even now, after being dumped with snow, the hairy stems and narrow leaves are there.

Of course, that wasn’t always true. The seedlings I repeatedly bought from a Santa Fe nursery were root bound with a film between the rootballs and plastic containers. They never survived. Finally, in 2006, cheaper plants arrived in the local hardware and they’re the ones that took hold in my windswept island bed with pinks and coral bells.

And of course, they didn’t always exist. However, the Cerastium genus has been around longer than Europe and Asia or North and South America have been joined. Back during the Miocene, 5.1 to 24.6 million years ago, the seas were receding and grasses were dominant. Members of the genus crossed the Bearing land bridge in the same general period grazing mammals moved across.

Today, Cerastium tomentosum lives in the central and southern Apennines of Italy, which themselves didn’t exist until the African plate collided with the peninsula in the Miocene and pushed up the limestone seabed. The five-petaled white flowers can be seen blooming in spring around Pescasseroli in the Abruzzi National Park and are found in the Giardino Botanico Daniela Brescia in the more rugged Majella National Park to the north.

Whether these plants are the relics of some earlier species with a wider distribution isn’t known. What has confounded botanists is that plants with very similar, but slightly different characteristics, have been found from Spain to the Balkans and Caucasus, while at least six closely related, separate species have been identified in Italy.

These members of the carnation family weren’t always considered a desirable garden flower. William Robinson published a suggestion in 1876 that the plants provided a suitable contrast to purple and crimson flowers and thought they could be used to “good effect in the wild garden” in 1903, but dismissed them as “edgings” in his more influential English Flower Garden.

Gertrude Jekyll seems to be the first to wax enthusiastic about their ability to grow in walls where their rhizomatous roots could seek cool water in the crevices. As she observed in 1901, any number of plants can live on flat land, but their “way of growing in hanging sheets is in itself a very interesting characteristic, pointing to the use of many beautiful things in circumstances that could not otherwise be dealt with so satisfactorily.”

By 1916, American Louise Beebe Wilder was covering her autumn crocuses with a “gray blanket of Cerastium” and two years later described stone steps nearly covered by a mat that began as “a frail thread of life in the top joint, has gradually felt its way, tumbling over the treads and running its green fingers along the transverse joints and on, until the hard lines of the steps are quite lost beneath the soft gray covering that does not suffer in the least from being walked upon.”

The tomentosum subspecies that’s been used in gardens is as variable and adaptable as its wild cousins. The species that spread through the arctic sometime during recent geologic time appears in forms with 8 or 12 sets of chromosomes and crossbreeds with the tetraploid Cerastium arvense.

When snow-in-summer finally began to be widely planted in England, it escaped and, by 1960, was wild everywhere on the island. Most specimens are octoploids (2n=72) that also cross themselves with arvense. On this continent, they’ve naturalized in a narrow belt from Nebraska west. The perennial is more common from Wisconsin east to the Atlantic and up into eastern Canada, where it also has 8 sets of chromosomes and hybridizes with an introduced arvense subspecies.

It’s true the plant can adapt to a wide variety of conditions, including roof gardens, but it’s also apparent to botanists that its method of adaptation is not the usual one of natural selection and potentially decreasing biodiversity. Instead, Cerastium has kept an open definition from its Miocene days of its genetic structure which allows its species to exist by expanding, not limiting, their genomes.

Notes:
Brysting, Anne K, Bengt Oxelman, Katharina T. Huber, Vincent Moulton and Christian Brochmann. “Untangling Complex Histories of Genome Mergings in High Polyploids,” Systematic Biology 56:467-476:2007.

Jekyll, Gertrude. Wall and Water Gardens, 1901.

Khalaf, M. K. and C. A. Stace. “The Distinction between Cerastium tomentosum L. and C. biebersteinii DC. (Caryophyllaceae), and Their Occurrence in the Wild in Britain,” Watsonia 23:481-491:2001.

Morton, John K. “Cerastium tomemtosum” at efloras Flora of North America website.

Robinson, William. The English Flower Garden, 1933 edition reprinted by Sagapress, Inc., 1984.

_____. The Garden, anonymous article, “Effective Mixed Flower Beds,” 1876.

_____. The Wild Garden, 1903.

Scheen, Anne-Cathrine, Christian Brochmann, Anne K. Brysting, Reidar Elven, Ashley Morris, Douglas E. Soltis, Pamela S. Soltis and Victor A. Albert. “Northern Hemisphere Biogeography of Cerastium (Caryophyllaceae): Insights from Phylogenetic Analysis of Noncoding Plastidnucleotide Sequences,” American Journal of Botany 91:943-952:2004.

Wilder, Louise Beebe. Colour in My Garden, 1918.

_____. My Garden, 1916.

Photograph: Snow-in-summer under a glaze of snow, 31 December 2009; taller leaves and akimbo branches are cheddar pinks.