The undisputed queen of the late-summer cut flower garden
| Type | Tender perennial (tuber) |
|---|---|
| Zones | 8–11 (lift tubers elsewhere) |
| Sun | Full sun, 6–8 hours |
| Height | 1–6 feet depending on variety |
| Bloom Season | Midsummer through first frost |
| Vase Life | 4–6 days |
| Start | Plant tubers after last frost |
Dahlias are one of the most rewarding flowers you can grow for cutting. A single tuber can produce dozens of stems over the course of a season, and the range of flower forms—from tight pompons to giant dinner plates—means there is a dahlia for every arrangement style.
Not all dahlias make great cut flowers. Look for varieties with long, sturdy stems and blooms in the 3–5 inch range. Ball, pompon, and decorative forms tend to have the best vase life. Dinner plate varieties look stunning but often droop in arrangements unless the stems are very thick. Some reliable cutting varieties include 'Cafe au Lait', 'Cornel Bronze', 'Jowey Winnie', and 'Wizard of Oz'.
Wait until the soil has warmed to at least 60°F before planting. Dig a hole about 6 inches deep, lay the tuber on its side with the eye (growth point) facing up, and cover. Do not water at planting—the tuber holds enough moisture to sprout. Space plants 18–24 inches apart. In shorter-season climates, you can start tubers in pots indoors 4–6 weeks before your last frost date to get a head start.
When the plant reaches about 12 inches tall with 3–4 sets of leaves, pinch out the center growing tip. This encourages the plant to branch and produce many more stems rather than one tall central stalk. Stake or cage the plant early—once dahlias get going they become heavy and will topple without support. A single sturdy stake per plant with garden twine works well, or use horizontal netting for rows.
Dahlias are heavy feeders. Work compost into the bed before planting and apply a balanced fertilizer every 3–4 weeks once plants are actively growing. See the fertilizing guide for specific recommendations. Water deeply once or twice a week rather than frequent shallow watering. Mulch around plants to retain moisture and suppress weeds.
Remove spent blooms regularly—this redirects energy into new buds. Watch for slugs early in the season, and keep an eye out for spider mites in hot, dry weather. Our pest control guide covers organic options.
Cut dahlias when blooms are about three-quarters to fully open. Unlike many flowers, dahlias do not continue to open after cutting. Harvest in the cool morning and plunge stems immediately into cool water. Use sharp, clean snips and cut stems at least 12–18 inches long. See the general harvest timing guide for more detail.
Dahlias benefit from a hot water treatment. Dip the bottom inch of freshly cut stems in near-boiling water for a few seconds, then transfer to a bucket of cool water and let them hydrate in a cool, dark place for several hours. Use clean water and floral preservative in the vase. Expect 4–6 days of vase life with proper care. More details in the conditioning guide.
In zones 8 and warmer, dahlias can be left in the ground with a thick mulch over winter. Everywhere else, dig tubers after the first frost has blackened the foliage. Rinse, let them dry for a day, then store in slightly damp peat moss or vermiculite in a cool (40–50°F), dark place. Check monthly for rot. Full instructions in the overwintering guide.
Dahlias are statement flowers. Use them as focal points in garden-style arrangements, pairing them with airy fillers like cosmos or ornamental grasses. They also look stunning on their own in a single-variety arrangement—a dozen 'Cafe au Lait' dahlias in a simple ceramic vase is hard to beat.
External: American Dahlia Society