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WW Man’s Garden Produces Dahlia with Unusual Coloration

September 4th, 2021

by Annie Charnley Eveland, The Walla Walla Valley Weekly

Dahlias inspire poetry and blooms wax beautifully in Walla Walla as many a garden will attest. Their lovely, cheery blossoms greet us all summer and surprise their cultivators with their many guises of petal shapes, sizes and hues.

Walla Wallan Gerald Hixson dropped by the office on Sept. 23 to show me this striking red and yellow dahlia. Half its petals are solid red and the other half a variegated sunny yellow and red pattern that makes me think of candy cane stripes or Morse code dots and dashes. Gerald’s plants yielded just the solo blossom thus far. “Up to that point it is the only one of its kind in my garden,” he said. I queried Professor Virginia Walbot with the Stanford University Department of Biology to find out a bit more about it.

I found her at The Stanford Dahlia Project website and emailed her this image of Gerald’s flower.
Emailing back the same day, she mused, “I think the variety is gloriosa. The coloration with half in red is likely caused by transposable elements.”
A further search online defines a “transposable element (as) a DNA sequence that can change its position within a genome, sometimes creating or reversing mutations and altering the cell’s genome size. Transposition often results in duplication of the transposable element.”

Wanting more information about the flowers, I couldn’t let sleeping dahlias lie. The tuberous perennial originated in Mexico. The garden plants are related to sunflowers, daisies, chrysanthemums and zinnias. Wikipedia says there are 42 dahlia species.

The flowers can grow on bushy greenery one head per stem and about two inches in diameter and up to 12 inches across — or dinner plate in size — on stems from 12 inches in height to a towering six to eight feet tall.

“This great variety results from dahlias being octoploids — that is, they have eight sets of homologous chromosomes, whereas most plants have only two. In addition, dahlias also contain many transposons — genetic pieces that move from place to place upon an allele — which contributes to their manifesting such great diversity.”

The majority of species do not produce scented flowers or cultivars. Like most plants that don’t attract pollinating insects through scent, they exhibit bright colors in most hues, all except for blue.

Mexico declared the dahlia its national flower in 1963. Aztecs grew the tubers as a food crop, but its use mostly died out after the Spanish Conquest (starting in 1519). Attempts to introduce the tubers as a food crop in Europe failed.

And because of Lady Holland, the new dahlia sambucifolia species was successfully grown in 1804 at Holland House, Kensington, England. She received either dahlia seeds or tubers while in Madrid that year and sent them to England to Lord Holland’s librarian Mr. Buonaiuti at Holland House, who raised them.

A year later, Buonaiuti produced two double flowers. The plants raised in 1804 did not survive; new stock was brought from France in 1815.

“The dahlia you brought to our isle
Your praises forever shall speak;
Mid gardens as sweet as your smile,
And in colour as bright as your cheek.”

— Lord Henry Richard Vassall-Fox, 3rd Baron Holland, in a note to wife Elizabeth Vassal Fox, Lady Holland, in 1824

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