MY FIRST ENCOUNTER WITH the genus Dahlia (D. spp.) began when I was getting ready for Brownie camp. Because I had to receive medical approval before being sent to the woods, I visited our family doctor. While sitting in the waiting room, I became enchanted with a still life hanging on the opposite wall. It was a painting of the most beautiful flowers I had ever seen. They were spilling—nearly tumbling—from a vase. No adult I knew had a garden that included these chrysanthemum-like pom-poms. I ached to know their identities. I was so smitten with this 19th–century reproduction that it’s still etched in my memory. I had no trouble discovering its creator, Dutch painter Georgius Jacobus Johannes van Os, for this article.
Modern dahlias, which are tuber-rooted members of the daisy family, are the progeny of D. pinnata and D. coccinea. Spanish explorers discovered both species growing in Mexico and shipped specimens back to the Royal Botanical Gardens in Madrid. A Swedish guest scientist named Andreas Dahl (hence the name “Dahlia”) began experimenting with them. Could those plump roots become a lucrative food commodity?Thanks to Dahl, his namesake became a wildly popular 19th–century European edible. Well, sort of. The French, including their livestock, refused to eat them, but, at least for a while, the British managed to pass dahlia tubers off as Jerusalem artichokes. Finally, after someone discovered that breeding dahlia into double-flowered forms was more profitable than hoodwinking folks into ingesting them, the English began selling dahlia to gardeners.
Dahlia’s ability to easily hybridize has given gardeners a color pallet choice that includes every hue but blue. Because it has been “engineered” to grow from 6 inches to 6 feet tall, dahlia fits anywhere in a herbaceous border. However, it’s their flower-head size and varied shapes that set these annuals/perennials apart from other garden plants.
In order to maintain some semblance of horticultural order, The American Dahlia Society (dahlia.org) recognizes 20 classes of blossom shapes and nine categories of bloom size. If you can’t find one that suits your fancy, you’re probably not looking hard enough. Still can’t find the dahlia of your dreams? Put those green thumbs to work and create a new one.
When it comes to designing exceptional landscapes, curious and determined gardeners have always found ways to bend the rules or take risks. To them it doesn’t matter that many Deep South gardeners have been fooled into believing that dahlias have about the same survival rate as peony (Paeoniae). Naysayers believe that, like peony, dahlia will never bloom because our summertime wet heat is too much for them or the scourge of our unique brands of disease will do them in.
Ha! While I’ve never seen a single peony growing in Charleston, I once admired a swath of terra-cotta-colored dahlia growing along a sea island roadside in the middle of July. I also recall a tall white variety that stood at attention in the middle of a gated entrance all summer long.
As with most tubers—including begonia and potato, as well as dahlia—disease sometimes happens. Take preventative measures and purchase only firm, blemish-free tubers and plant at the recommended depth. Also, leaf and stem afflictions might appear, especially if plants are spaced too close. Aphids and thrips are also vectors of disease. But even with these caveats, I don’t think dahlia is any more delicate than other garden favorites. To prove my point, I grew from seed a garnet-colored single-blossom variety named ‘Bishop’s Children’ (D. variabilis). It survived for several years without issue, even after I ignored instructions to dig out the tubers and overwinter them in pots.
Dahlia requires six to eight hours of sun and well-drained, organic-rich soil. Avoid manures and high nitrogen fertilizers, which boost leaf growth at the expense of flowering. Instead, all dahlia prefer a fertilizer that is light on nitrogen (the first number on the package) and rich in phosphorus (second number) and potassium (third number). An often-recommended blend is 5–10–10. Fertilize every three to four weeks until bloom begins.
For those who don’t tend a garden but love to look at dahlia, reproductions of my beloved van Os painting, titled Still Life of Flowers, are available as well as Paul Cézanne’s Dahlias and Bouquet of Yellow Dahlias. Dahlia motifs began to show up in wallpaper patterns during the mid 18th–century, and modern renditions lend an authentic flair to Charleston homes. Fabrics printed with dahlia designs were popular in the 1960s. I should know. My favorite summertime dress was a cream and pink dahlia-covered shift.*
PJ Gartin is a freelance garden writer who lives in Charleston.