Sunday, November 16, 2008

Pasture Rose

What’s blooming: Freeze dried purple aster by front gate; many trees still hold dead leaves; one family has bagged their dead debris while their neighbors were burning yesterday.
What’s still green: Juniper, arborvitae and other conifers, roses, yucca, prickly pear, honeysuckle, red hot poker, vinca, rock rose, hartweig, yellow evening primrose, blue flax, sea pink, winecup, pinks, soapworts, bouncing Bess, beardtongues, snapdragon, Jupiter’s beard, snakeweed, senecio, yarrow, Mount Atlas daisy, Mexican hat, chocolate flower, June and other grasses, alfalfa; only protected leaves survive on sweet pea, hollyhock, catmint, chrysanthemum and purple coneflower
What’s gray, blue or gray-green: Piñon, winterfat, saltbush, buddleia, loco, snow-in-summer, yellow alyssum, chamisa, Silver King artemisia.
What’s red or orange: Pasture rose, spirea, raspberry, cholla, privet, coral bells, white beardtongue, pink evening primrose.
What’s turning yellow: Cottonwood, willow, globe willow, Apache plume, iris, Saint John’s wort, golden spur columbine.
What’s blooming inside: Aptenia, rochea, bougainvillea; Christmas cactus leaves turning red.
Animal sightings: Brown bird with dark head in cherry; horses brought in to browse mown alfalfa field down the road.
Weather: Rain Monday with heavy frost on windshield subsequent mornings when temperatures fell to high 20's after dawn; 9:13 hours of daylight today.
Weekly update: A run of mornings with consistently cool temperatures this year has given the valley something rare: fall color. Not only have huge cottonwoods changed into golden domes, but tamarixes and other small-leaved plants have transmuted into orange-shaded lattices. The sand cherries turned their usual purple, but here and there some neighbors’ shrubs have been the brilliant red of maples.
In my yard, the pasture roses have been the most amazing because they not only turned red, but the leaves glowed when light filtered through them. The maroon raspberries at their feet were comparative dullards, opaque ground-hugging triangles of hairy corduroy.
The reds come from anthocyanins, flavonid chemicals formed by interactions between sugars and proteins that protect plant tissues by absorbing ultraviolet light. They become more prevalent in leaves when cool weather slows the production of chlorophyl and other protective agents are generated. With many hybrid roses, the new growth is red until photosynthesis accelerates. On some cultivars, the leaves keep a red edge long into the blooming season.
In the fall most hybrid rose leaves darken, then dry and fall from stems that tend to stay green all winter. The only other roses I have that shaded into burgundy this year have been the crenellated rugosas. The precise shade of an anthocyanin red is determined by the pH in the plant sap, which in turn is controlled by the soil: the more alkaline the soil, the bluer the color.
Japanese scientists have been curious about the distribution of the some 550 anthocyanins so far identified. Among wild and cultivated roses they found chemical patterns identified three subgroups within the Rosa genus: one the gallica, chinensis, Synstylae (including winchurana, musk and multiflora), Cherokee, Macartney and Banksia, another the species of Scotch roses, and a third which includes dog, carolina, and cinnamon roses.

Volker Wissemann and Christiane Ritz found members of the last two groups did not share the same DNA patterns as the first. Others found the carolinas, native to eastern North America, are natural scions of Rosa arkansana and Rosa virginiana, both themselves natural hybrids of other native roses. Apparently, as the plants evolved on two continents, the chemistry of the American roses diverged from the Eurasian ones originally used to create modern hybrids.

I got my carolina rose through one of those impulses that happen after one has dutifully pruned one’s wish list to fit the budget, and then said, "oh why not" when filling out the order form. In 1998 I bought seeds from Prairie Nursery, blithely ignoring the warning that the "seeds are double dormant and require treatment to break dormancy and induce germination." When nothing sprouted I shrugged.

Four years later, in 2002, I noticed what looked like rose leaves in the drip line where I had dropped some 300 seeds and wondered, but I cautioned myself with memories of other briars that had looked like roses only to become unwelcome pests. Leaves continued to appear each year, teasing me with possibilities, and then colonized last year among the raspberry canes.

Then on June 10 a single pink flower appeared, and I knew I had grown a carolina rose from seed. That doesn’t sound like much if you live where pasture roses sucker into great thickets, but here the "dry prairie" of a Wisconsin seed company is only a wet dream. Even if all I ever get are leaves, I now know at least once a decade, when the fall is both cool and dry, I’m going to have the most spectacular red leaves in the valley.

Notes:Joly, Simon, Julian R. Starr, Walter H. Lewis and Anne Bruneau. "Polyploid and Hybrid Evolution in Roses East of the Rocky Mountains," American Journal of Botany 93:412-425:2006.

Mikanagi, Yuki, Masato Yokoi, Norio Saito and Yoshihiro Ueda. "Flower Flavonol and Anthocyanin Distribution in Subgenus Rosa," Biochemical Systematics and Ecology 23:183-200:1995.

Prairie Nursery. Wildflowers and Native Grasses, 1996 catalog.

Wissemann, Vilker and Christiane M. Ritz. "The Genus Rosa (Rosoideae, Rosaceae) Revisited: Molecular Analysis of nrITS-1 and atpB-rbcL Intergenic Spacer (IGS) versus Conventional Taxonomy," Linnean Society Botanical Journal 147:275 - 290:2005.

Photograph: Pasture rose, 9 November 2008, with darker raspberry leaves at bottom left and native grasses in rear.

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