Dahlia
Plant tubers only once frost danger has passed and the soil has warmed; earwigs are the classic dahlia headache and shred petals overnight, so trap them with rolled newspaper or diatomaceous earth. Taller varieties need staking.
- Sun
- full sun
- Water
- moderate
- Spacing
- 50cm
- Difficulty
- beginner
- Grows in
- Whangārei / Northland, Auckland, Hamilton / Waikato, Tauranga / Bay of Plenty, Gisborne, Napier / Hawke's Bay, New Plymouth / Taranaki, Palmerston North / Manawatū-Whanganui, Wellington, Nelson, Tasman, Blenheim / Marlborough, West Coast, Christchurch / Canterbury, Dunedin / Otago, Invercargill / Southland
- Mature height
- 1.5m
- Flowering season
- Jan, Feb, Mar, Apr
- Attracts wildlife
- Bees, Butterflies
- Common diseases
- Powdery mildew
- Common pests
- Earwigs, Slugs and snails
When to plant by region
In Whangārei / Northland, Auckland, Tauranga / Bay of Plenty, Gisborne and Napier / Hawke's Bay: September-October. In Hamilton / Waikato, New Plymouth / Taranaki, Palmerston North / Manawatū-Whanganui, Wellington, Nelson, Tasman, Blenheim / Marlborough, West Coast and Christchurch / Canterbury: October-November. In Dunedin / Otago and Invercargill / Southland: November.
Growing stages
Germination & plantingOnce frost danger has passed and soil has warmed
- Wait until frost danger has passed and soil has warmed before planting tubers, cold wet soil rots them
- Space tubers around 50cm apart to allow for their mature spread
Establishment
- Watch for earwigs, the classic dahlia pest, feeding on soft new shoots as well as petals
- Trap earwigs with rolled newspaper or diatomaceous earth around emerging shoots
- Slugs and snails can also target young growth
Vegetative growth
- Taller varieties reach up to 150cm and need staking before they get top-heavy
- Water moderately and consistently as foliage bulks up
- Powdery mildew can develop on leaves, especially in humid conditions with poor airflow
Flowering
- Earwigs shred petals overnight, so keep trapping through the flowering season
- Deadhead regularly to keep blooms coming, and cut flowers for the vase
- Bees and butterflies visit the blooms, so avoid spraying open flowers with insecticide
Dieback & dormancy
- Foliage blackens and collapses after the first autumn frosts
- Lift and store tubers over winter in cold areas, or mulch heavily to protect them in mild ones
- Cut stems back once foliage has collapsed