How to Grow Dahlias: Complete Planting & Care Guide
From humble tubers to showstopping blooms. Everything you need to know to grow gorgeous dahlias in your garden.
Dahlias are the royalty of the late summer garden. With blooms ranging from 2 inches to dinner-plate-sized 12 inches, and every color except blue, learning how to grow dahlias opens up endless possibilities for stunning garden displays and cut flower arrangements.
Dahlia Basics
Growing Requirements
- - Full sun (6-8 hours)
- - Rich, well-drained soil
- - Regular watering
- - Zone 8-11 (annual elsewhere)
Bloom Time
- - Mid-summer to first frost
- - Peak: August-October
- - 8-12 weeks from planting
- - Continuous with deadheading
Flower Types
- - Dinnerplate (8-12")
- - Decorative
- - Ball & Pompon
- - Cactus & Semi-cactus
Planting Dahlia Tubers
Timing is Everything
Plant dahlia tubers after your last frost date when soil has warmed to at least 60°F (15°C). Too early = rotting tubers. In cold climates, start tubers indoors 4-6 weeks early for a head start.
Step-by-Step Planting
- 1Prepare the soil
Dig in compost and ensure good drainage. Dahlias hate wet feet.
- 2Dig a hole 6-8 inches deep
Wide enough to lay the tuber flat.
- 3Install your stake NOW
Put in a 4-5 foot stake before planting to avoid damaging roots later.
- 4Position tuber horizontally
Eye (growing point) facing up. Cover with 2-3 inches of soil.
- 5Don't water yet!
Wait until green growth appears to avoid rotting the tuber.
- 6Space appropriately
18-24 inches apart for small varieties, 3 feet for dinnerplate types.
The Secret to More Blooms: Pinching
When your dahlia reaches 12-16 inches tall with 4-5 sets of leaves, pinch out the center growing tip. This creates a bushier plant with more flowering stems—and many more blooms.
Unpinched Dahlia
- - Single tall stem
- - Fewer, larger blooms
- - Blooms earlier
- - May need more staking
Pinched Dahlia
- - Multiple branching stems
- - Many more flowers
- - Slightly later blooming
- - Stockier, bushier plant
Ongoing Care
Watering
Deep watering 2-3 times per week once plants are growing. Drip irrigation or soaker hoses are ideal. Avoid wetting foliage to prevent disease.
Fertilizing
Feed monthly with a low-nitrogen fertilizer (5-10-10 or similar). Too much nitrogen = lots of leaves, few flowers. Stop fertilizing in late summer.
Staking
All but the smallest dahlias need support. Tie stems loosely to stakes as they grow. Tomato cages also work well for bushier varieties.
Deadheading
Remove spent blooms promptly to encourage more flowers. Cut back to a leaf node or side branch. The more you cut for bouquets, the more they bloom.
Common Dahlia Problems
Pests
- Slugs/Snails: Use bait or copper tape around plants
- Aphids: Spray with water or insecticidal soap
- Spider mites: Increase humidity, spray undersides of leaves
- Earwigs: Set traps with oil in shallow containers
Diseases
- Powdery mildew: Improve air circulation, avoid overhead watering
- Botrytis: Remove affected blooms, improve ventilation
- Viral diseases: Remove and destroy affected plants
- Tuber rot: Ensure drainage, don't overwater
Overwintering Dahlia Tubers
In zones 8-11, dahlias can stay in the ground with mulch protection. In colder zones, you'll need to dig and store tubers.
Digging & Storing Tubers
- 1. Wait for frost to blacken foliage
- 2. Cut stems back to 4-6 inches
- 3. Carefully dig around the clump, 12 inches out from stems
- 4. Rinse off soil and let tubers dry for a day
- 5. Divide clumps (optional) or store whole
- 6. Pack in vermiculite, peat moss, or wood shavings
- 7. Store at 40-50°F in a dark, dry place
- 8. Check monthly for rot or shriveling
Best Dahlia Varieties for Beginners
Café au Lait
Creamy blush 10" blooms. Wedding favorite. Vigorous grower.
Bishop of Llandaff
Scarlet single blooms with dark burgundy foliage. Compact.
Thomas Edison
Deep purple 6-8" blooms. Reliable and prolific.
Gallery Art Deco
Peach-orange compact variety. Great for containers.
Wizard of Oz
Pink ball dahlia with tight, perfect form. Long vase life.
Arabian Night
Nearly black-red 4" decorative. Dramatic and elegant.
Frequently Asked Questions
Why aren't my dahlias blooming?
Common causes: too much nitrogen fertilizer, not enough sun, planted too late in the season, or plants are still establishing. Most dahlias need 8-12 weeks to bloom.
Can I grow dahlias from seed?
Yes, but seedlings won't be true to the parent plant. Seeds are often sold as mixes. Tubers are the best way to get specific varieties.
How long do cut dahlias last?
5-7 days in a vase. Cut in the morning when blooms are 3/4 open. Use hot water (not boiling) and change water daily.
Once you start growing dahlias, you'll likely become obsessed—and that's a wonderful thing. These magnificent flowers reward your care with an endless parade of blooms from midsummer until frost, making them one of the most rewarding flowers you can grow.
Local Flower Team
Local Flower
The Local Flower team is dedicated to helping you discover beautiful blooms and connect with talented florists in your area.