How to Grow Dahlia
Dahlia At a Glance
Difficulty
Moderate
Category
Flower
Sun Exposure
Full Sun
Frost Tolerance
Frost Tender
Cold Hardiness
Survives to -1°C
Plant Family
Asteraceae
Growing Season
Warm Season
Plant Lifecycle
Perennial
How to Start It
★ Recommended for beginners
Plant dahlia tubers about 1 week after your last spring frost, once the soil has warmed. Lay each tuber on its side 10 to 15 cm deep, with the old stem or any small bud (the eye) pointing up, and space them 45 cm apart. Do not water until green shoots appear, since a wet tuber with no leaves can rot. Shoots usually show in 2 to 4 weeks.
Dahlias flower nonstop from midsummer until the first fall frost, and the more you cut, the more they bloom. They cannot survive a Canadian winter in the ground, so dig up the tubers each fall and store them indoors, and each one comes back bigger the next year.
When To Start
Dahlia needs warmth. Wait until your last frost has passed and the soil has warmed before sowing.
We do not have exact sowing dates for this one yet.
When should you plant Dahlia?
Your planting dates depend on your local climate. Sign up and add your location to unlock personalized dates.
Your Dahlia Planting Window
Start planting
May 15, 2026
Last chance
Sep 10, 2026
Your Dahlia Calendar
Set your location to turn these into exact dates and reminders.
Plant dahlia tubers on their side, eye up
1 week after your last frost· every year
Pinch dahlia tips for bushier plants, stake tall ones
5 weeks after your last frost· every year· optional
Cut dahlias often, the more you cut, the more they bloom
90 days after your last frost· every year· optional
Dig up and store dahlia tubers after the first frost
3 days after your first frost· every year· optional
Water your new dahlia plants well while they settle in. Deep and slow is best.
About 1 days after you plant it
How are your dahlias doing? Once shoots are up, water deeply once a week.
About 30 days after you plant it
Dahlia check! Stake tall stems, and cut flowers often to keep more coming.
About 90 days after you plant it
The Journey Ahead
Dahlia's Lifecycle
Seedling
Mature Plant
Seed Production
Step 2
Planting & Sprouting
Growing Tips
- 1Give dahlias full sun, at least 6 to 8 hours a day.
- 2Plant them in loose, rich soil with plenty of compost mixed in, which drains well so the tubers do not rot.
- 3Once the plants are growing, water deeply once or twice a week in summer, and feed with worm castings or compost tea every 3 to 4 weeks once the buds form.
- 4When a young plant has 3 or 4 pairs of leaves, pinch out the tip to make it bushier, and push a stake in beside tall types at planting time so you do not stab the tuber later.
- 5Pick slugs off young shoots in the evening, and shake earwigs out of the flowers.
- 6Dahlias can upset a cat's or dog's stomach if eaten, so keep chewing pets away.
Seedling Phase
Step 3
Growth & Maturity
120 cm
Mature Height
60 cm
Mature Width
Pests to Watch For
Diseases to Watch For
Mature Plant
Step 4
Harvesting
When to Pick
Blooms midsummer to first frost; the more you cut, the more it flowers
How to Harvest
- 1Cut dahlias in the cool of the morning when the flowers are almost or fully open, since the buds barely open more once cut.
- 2Cut a long stem just above a pair of leaves and put it straight into cool water.
- 3Snip off faded flowers every few days: a faded flower is pointed like a cone, while a new bud is round.
- 4After the first fall frost blackens the leaves, cut the stems down to 10 cm and dig up the clump with a fork, taking care not to stab it.
- 5Let the tubers dry for a day, then store them in a box of dry peat moss or wood shavings somewhere cool and frost free, around 4 to 7°C (40 to 45°F), until spring.
Step 5
Saving Seeds
Seed Production
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