Nancy Parker
Where to buy dahlia seeds and tubers: Burpee Gardening
In cooler North American climates, dahlias grow as tuberous-rooted tender perennials, planted in spring from small brown biennial tubers. These vibrant, spiky flowers bloom from midsummer until the first frost, stealing the show when many other plants have faded. They offer incredible diversity—from giant 10-inch "dinnerplate" blooms to 2-inch lollipop-style pompons—in a dazzling color range. Most varieties reach 4 to 5 feet tall.
While dahlias struggle in extremely hot, humid regions like much of Texas and Florida, they thrive in sunny gardens with a growing season of at least 120 days. The cool, moist climate of the Pacific Coast is ideal, often producing blooms an inch larger and deeper in color.
Planting Dahlias for Spectacular Blooms
- Timing is everything: Don't rush. Dahlias sulk in cold soil. Wait until ground temperature reaches 60°F and all frost danger has passed—typically around when you plant tomatoes.
- Sun and shelter: Choose a site with 6–8 hours of direct sun (morning sun is best) and some wind protection.
- Soil prep: Dahlias need rich, well-drained soil with a pH of 6.5–7.0. Amend heavy soil with sand, peat moss, or composted manure to improve drainage.
- Spacing: Bedding types: 9–12 inches apart. Smaller varieties (3 ft tall): 2 feet apart. Tall, large-flowered types: 3 feet apart.
- Planting technique: Dig a hole larger than the root ball. Mix in compost or peat moss plus a handful of bonemeal. Avoid other fertilizers at planting.
- Select healthy tubers: Avoid wrinkled or rotten ones. A bit of green growth is a good sign. Never cut or break tubers like potatoes—plant them whole with "eyes" facing up, 6–8 inches deep, crowns just above soil level.
- Stake early: Tall varieties need 5–6 ft stakes placed at planting time to avoid damaging tubers later.
- Garden placement: Large dahlias and cutting varieties do best in dedicated rows. Medium-height types mix well with other summer flowers. They're also perfect for a vegetable garden row.
- Bloom timeline: Expect flowers about 8 weeks after planting, starting mid-July.
- Head start: Start tubers indoors a month early for earlier blooms.
- Water wisely: Don't water after planting—this invites rot. Wait until sprouts emerge.
- Skip mulch: Mulch hinders sprouting. Apply slug/snail bait instead.
Care Throughout the Season
- Watering: No water until plants appear. Once established, deep water 2–3 times weekly for 30+ minutes (more in hot, dry climates).
- Fertilizing: Use low-nitrogen liquid fertilizer (5-10-10 or 10-20-20) after sprouting, then every 3–4 weeks until early autumn. Avoid excess nitrogen—it yields weak tubers and few blooms.
- Weather protection: Large blooms collect water and suffer in wind; check plants after rain.
- Pinching and deadheading: Bedding dahlias: pinch center shoot above the third leaf set for bushiness; deadhead faded flowers. Taller types: stake at planting, moderately pinch/disbud/deadhead for 3+ months of showy display.
- Frost response: Foliage blackens at first frost.
- Overwintering: Hardy to Zone 8. In Zone 8, cut back and mulch deeply. In colder zones, lift and store tubers. Some gardeners report survival in Zone 7 with mild winters.
Pests and Diseases
- Slugs/snails: Bait 2 weeks after planting and continue all season.
- Mites: Spray for spider mites from late July through September.
- Earwigs & cucumber beetles: Eat petals but don't harm the plant.
- Aphids
- Deer: Plant deer-resistant companions nearby.
- Powdery mildew: Common in fall; spray preventatively from late July to August.
Harvest and Winter Storage
Lifting and Storing Tubers
In cold regions, dig tubers in early fall to save them. Dahlias may survive in Zone 8 if left in ground. A light frost helps trigger dormancy in Zones 5 and colder.
- Cut foliage to 2–4 inches above ground; lift and separate clumps.
- Gently shake off soil.
- Remove rotten tubers; dry the rest upside down naturally.
- Pack in loose material (vermiculite, dry sand, Styrofoam peanuts).
- Store in a well-ventilated, frost-free spot at 40–45°F (35–50°F acceptable).
- In spring, separate tubers from the parent clump and replant.
- If storage seems daunting, simply buy new tubers each spring.
Recommended Varieties
Choosing a favorite dahlia is like exploring a button box—endless color, size, and shape combinations. Popular picks:
- 'Bishop of Llandaff' – Small, intense scarlet flowers with dark burgundy foliage.
- 'Miss Rose Fletcher' – Elegant pink cactus type with 6-inch quilled, shell-pink globes.
- 'Bonne Esperance' ('Good Hope') – Foot-tall dwarf with 1½-inch rosy-pink daisies all summer.
- 'Kidd's Climax' – Spectacular 10-inch "dinnerplate" blooms with hundreds of pink petals suffused with gold.
- 'Jersey's Beauty' – 7-foot pink giant with hand-sized flowers for fall energy.
Wit & Wisdom
The dahlia honors Anders Dahl (botanist), born March 17, 1751.
The Dahlia you brought to our isle
Your praises forever shall speak
'Mid gardens as sweet as your smile
And colour as bright as your cheek.
–Lord Holland (1773–1840)
