Sunday, January 17, 2010

Shasta Daisy

What’s still green: Arborvitae, juniper and other evergreens, Apache plume, some rose stems, cholla, prickly pear, yuccas, Japanese honeysuckle, vinca, beardtongues, coral bells, sea pink; snow still covers grape hyacinth, 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: Bougainvillea and aptenia; rochea and Christmas cactus leaves tinged with red.

Animal sightings: The birds that land in the peach don’t chirp or sing; they make clacking noises that sound like two sticks hitting one another.

Weather: Early morning temperature still dropping to mid-teens, but afternoons warming enough to thaw parts of the drive; last snow 12/30/09; 9:50 hours of daylight today.

Weekly update: Gardeners usually know what they do and why they do it. When they look at the consequences, they’re never sure exactly what happened. Nature has a way of intervening.

I wanted tall white flowers along the west side of the garage and so ordered six Shasta daisy seedlings in 1998 that didn’t survive. I planted six Alaska cultivars in 1999 and added six Exhibitions in 2000. Each started to bloom the following summer, until the grasshoppers found them. By 2003 they appeared to have died out, but one came back the next spring.

Every year since the cycle has been repeated. The one Alaska plant comes up; the grasshoppers eat the flowers before they fully open on stalks that never get more than 6" high. With this year’s atypical weather, the leaves were able to come back in the fall and even started to put out new growth before the snows of December finally collapsed the older leaves.

Luther Burbank knew what he wanted when he bred the Shasta daisy, a daisy that "would be the purest imaginable white in color" And he knew exactly what he did to create that whiteness.

He began growing ox-eye daisies in California and selected the best plants to fertilize with pollen from a Pyrenees flower, Leucanthemum maximum. The result had the grace of the maternal Leucanthemum vulgare, but the large flowers of the father. Still he thought them a bit dingy.

Next he tried adding the pollen from a Portugese daisy he ordered from Germany, Leucanthemum lacustre, but the improvement was minor. Then he tried the pollen from the Japanese Nipponanthemum nipponicum and produced a whiter, larger flower, but lost the leafless stalk he desired. He continued selecting the best of its offspring, until he got the "Shasta hybrids" he sold in 1901 and the Alaska he released in 1904.

What he didn’t know is how it all happened. He’d been inspired by Charles Darwin’s Variation of Animals and Plants under Domestication and was systematically applying the concept of natural selection with the methods then in use, controlling the pollination between two plants. He began by improving the fruits of members of the rose family like plums and blackberries.

When he began on daisies, all the perennials he used were considered members of the Chrysanthemum genus that had already been much improved. In the 1990's, taxonomists tried to rationalize the composite family into new genuses grouped within tribes and subtribes. They separated the Leucanthemums into what they believed was a monophyletic genus, meaning one that evolved from a common ancestor in Europe, possibly the Mediterranean area. The Japanese plant was redefined as a Nipponanthemum which was "provisionally placed as an aberrant member of subtribe Leucantheminae."

Tyge Böcher and Kai Larsen believe those Leucanthemum species that grow in England and Atlantic Europe tend to have the usual two sets of chromosomes, while those living elsewhere on the continent and in the southern mountains have many more. In fact, the widely distributed vulgare can vary from two to ten chromosomes, while maximum has ten and lacustre has 22. The Japanese plant has the usual two.

Botanists have found no universal rule governing the ability of closely related species to interbreed, but have found the greater the number of chromosome sets, the greater the possible variations, and often the greater the size of the plant, fruit or flowers.

Burbank couldn’t have known this in 1901 when he released Shasta daisies. In 1872, Edmund Russow had observed some rod shaped entities in cells during early mitosis just after the male and female cells had merged that subsequently change shape and then couldn’t be seen with an optical microscope. It wasn’t until Walther Flemming found a way to stain the cells with an aniline dye that chromosomes could be seen easily, but no one understood the significance of what they were seeing until the work of Gregor Mendel was publicized in 1900.

However, by the time Burbank described how he produced the Shasta daisy in 1914 he was aware, at least in general, of Mendel’s work. The 65-year-old man remembered "thousands of seedlings were raised each year for five or six ensuing seasons," the number of generations required by Mendel to assure a given trait will always appear. Without knowing the numbers of chromosomes, he also knew the possible permutations required he plant many more than four seeds.

None of his comments or intentions, of course, have anything to do with why Shasta daisies grow in a massed bed down the road, don’t survive three years for my next door neighbor, and behave like displaced persons in the icy drip line on the west side of my garage. The genes that make the taproot prefer heavy soil or require cold winter temperatures to bloom were outside his interest, but they are the natural forces that ultimately determine if Leucanthemum superbum can grow in this part of northern New Mexico.

Notes:
Böcher, Tyge W. and Kai Larsen. "Cytotaxonomical Studies in the Chrysanthemum Leucanthemum Complex," Watsonia 4:11-16:1958.

Bremer, Kare and Christopher John Humphries. "Generic Monograph of Asteraceae-Anthemideae," The Natural History Museum Bulletin 23:71-177 :1993.

Burbank, Luther, John Whitson, Robert John, and Henry Smith Williams. Luther Burbank: His Methods and Discoveries and Their Practical Application, volume 2, 1914; chapter 1 reprinted as Luther Burbank, The Shasta Daisy: How a Troublesome Weed Was Remade Into a Beautiful Flower, by Athena University Press, 2004.

Darwin, Charles. The Variation of Animals and Plants under Domestication, 1868, revised 1875.

Heide, O. M. "Dual Induction Control of Flowering in Leucanthemum vulgare," Physiologia Plantarum 95:159-165:1995.

Strother, John L. Chromosome counts from entries on Leucanthemum and Nipponanthemum on eFloras’ Flora of North America website.

Photograph: Shasta daisy "Alaska," 10 January 2010.

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