Dahlia nirvana – it’s a real thing! It starts with a single “spark” dahlia, maybe a dinner-plate-sized ‘Café Au Lait’ or a ball-shaped ‘Crichton Honey’. Pretty soon the flower bed is filled with dozens of dahlias and still you keep finding ways to squeeze in more. It’s no wonder. Dahlias are so spectacular in the late summer garden and make the prettiest bouquets.
At Groovy Plants Ranch, we sell flowering potted dahlias that make it easy for beginners to get started on this road to nirvana. Read on for more tips and background on this heavenly flower. We know you’ll be eternally grateful!
Dahlias belong to the Asteraceae family along with daisies and sunflowers. They grow naturally in high mountain regions of Mexico and Guatemala where the temperatures are cooler. According to the American Dahlia Society (ADS), early Spanish botanists discovered hollow-stemmed tree dahlias that the Aztecs used to haul water. Explorers brought dahlia seeds, tubers and plants to from central America to Spain and other European countries. The Madrid Botanical Gardens ended up naming the plant after Swedish botanist Anders Dahl who was especially interested in its tubers as a food source. Today, there are 42 recognized species and thousands of cultivars.
Dahlias bloom from midsummer until the first frost and in nearly every color except blue. Their sizes range from 2-inch pompoms to 10-inch dinner plate sizes. Most varieties grow four to five feet tall. They come in single-flowering types in orchid, anemone and peony shapes. They also come in double-flowering types including cactus, ball and pompom shapes. The ADS categorizes today’s dahlias by size, form, and color. Try growing them in cutting gardens, perennial borders or decorative containers.
Dahlias grow from a clump of underground tubers that look like potatoes. In spring, new sprouts emerge from the “eyes” where the tubers come together at the base of the stem. These tubers provide stored energy to fuel plants’ growth. They multiply and grow, so you will have more tubers by the end of a season.
Either purchase dahlia tubers for spring planting or get a jump start with blooming potted plants. To plant, select a sunny area with a minimum six hours of sun, preferably morning light and afternoon shade. Dahlias thrive in well-drained soil that has been enhanced with compost or manure. Tubers can be planted in early May, while potted plants can be planted anytime after the threat of frost. For tubers, remember to plant them with the “eye” of the tuber facing up.
Be sure to stake taller varieties with 5- to 7-foot stakes at planting time. Also, fertilize them at planting time then again when plants reach 18-24 inches tall (about July 1). In late June or early July once the soil has warmed, mulch around the plants with straw or grass clippings. This mulch layer plays an important role in cooling soil, conserving moisture and eliminating weeds. Dahlias need an adequate supply of moisture. Water at their bases as needed and water thoroughly but not excessively (which can lead to rotting tubers). Watch for insect damage either tolerating minimal injury, hand removing insects (e.g., slugs or Japanese beetles) or treating as needed (be sure to follow package instructions).
For larger blooms, try this disbudding technique. Once dahlias grow two to three sets of leaves, cut and remove the top to encourage branching. The denser and more compact the plants, the better the results will be. Continue to remove side buds to improve the size of the end blooms. The technique reduces the number of blooms but increases bloom sizes.
Digging and Storing Tubers
Dahlias are hardy in USDA zones 7 to 11. So, in northern zones, dahlia tubers must be dug and stored for the winter. Dig the tubers in late fall before the ground freezes. Brush off the soil and allow tubers to dry out in a garage for a week or two. Once dry, place tubers in a milk crate, Styrofoam cooler or cardboard box then cover them with wood shavings (from a farm store) or sawdust. Store them in a dark cool place (e.g., garage, unheated basement or utility room). For more details, see this article from ADS.
- Visit the American Dahlia Society (dahlia.org) for helpful tutorials and a directory of local chapters that host sales and workshops.
- Check out this British dahlia fanatic and her dahlia flower farm on Instagram @dahliabeach
- Read Discovering Dahlias by Erin Benzakein (Chronicle Books, 2021)
- Dahlia Types Explained - National Garden Bureau (ngb.org)