How to grow Zinnia in New Zealand
Zinnias are bright, easy summer annuals with bold flowers in almost every colour, from dahlia-like doubles to lime green and candy-striped types. They love heat and sun, make excellent long-lasting cut flowers, and bring bees and butterflies to the garden. The more you cut, the more they flower.
📖 Our full guide: How to Grow Zinnia in New Zealand
At a glance
When to sow by region
| Region | When to sow | Regional note |
|---|---|---|
| Northland | September to December | |
| Auckland | September to December | |
| Waikato & Bay of Plenty | October to December | Sow from October, once the inland frosts are over in late September. Warm coastal Bay of Plenty gardens can start a few weeks earlier under cover. |
| Central North Island | November and December | |
| Wellington & Lower North Island | October to December | |
| Nelson & Marlborough | October to December | |
| Canterbury | November and December | |
| Otago & Southland | November and December | |
| Central Otago | December |
Where to plant
Zinnias need full sun, warmth and some protection from strong winds, in free-draining soil rich in organic matter. They suit garden beds, cutting gardens and containers. Good air flow helps keep powdery mildew away.
- Northland and Auckland: sow from September once the soil warms.
- Waikato and the Bay of Plenty: sow from October, once the inland frosts are over.
- Wellington and Nelson: sow from October to December.
- Central North Island, Canterbury, Otago and Southland: sow in November and December; in Central Otago, in December.
Choosing a variety
- Tall dahlia-flowered types such as Gold Medal Mix or Giant Cactus reach about 1.2 m and are the best for cutting.
- Queen Lime and similar types come in unusual lime, blush and coral shades.
- Dwarf types such as Lilliput suit pots and edges.
- Candy-striped and swirled types add pattern to a cutting bed.
How to plant
- Sow seed directly where it is to grow once the soil is warm, lightly covered, and firm down. Zinnias resent root disturbance, so take care if raising them in trays.
- Keep moist while the seeds germinate.
- Thin seedlings to about 25 to 30 cm apart.
- When seedlings are about 5 cm tall, mulch around them.
- Pinch out the first flower bud or growing tip to encourage branching.
Watering and feeding
Water regularly at the base of the plant, keeping the leaves dry, which helps prevent powdery mildew. Feed every few weeks with a flowering fertiliser.
Pruning and care through the year
- Cut or deadhead flowers regularly to keep new ones coming.
- Stake tall varieties in windy spots.
- Space plants for air flow, and remove leaves badly affected by mildew.
Harvesting
Cut stems when the flowers are fully open and the stem is firm just below the flower head; zinnias do not open further once cut. They last well in a vase, especially if the water is changed often.
Growing in pots
Dwarf zinnias grow well in pots of quality container mix in full sun. Sow directly into the pot, keep moist while germinating, and water regularly at the base.
Companion planting
Zinnias bring in bees, butterflies and helpful insects, which benefit nearby summer crops.
Good companions
Pests and diseases
Powdery mildew is the main problem, especially in humid late summer weather.
Pests to watch for
- Aphids Clusters of insects on buds and shoot tips.
Diseases to watch for
- Powdery mildew White powdery coating on the leaves in late summer. Water at the base and space plants.
- Alternaria leaf spot Reddish-brown spots with grey centres on the leaves in warm, wet weather.
- Bacterial leaf spot Small, angular, water-soaked spots on leaves, spread by rain and overhead watering.
Common questions
When should I sow zinnias in New Zealand?
Once the soil has warmed in spring: from September in the north and November or December in the south. Zinnias are frost tender and love heat.
How do I stop powdery mildew on zinnias?
Water at the base rather than over the leaves, give plants space for air flow, and grow them in full sun. Remove the worst-affected leaves.
Can I transplant zinnia seedlings?
Yes, with care, as they resent root disturbance. Sowing directly where they are to grow is easiest.
How do I get more flowers on zinnias?
Pinch out the first bud or growing tip to encourage branching, and keep cutting flowers. The more you cut, the more they flower.
Are zinnias good for bees?
Yes. Zinnias attract bees and butterflies, which also helps pollinate nearby vegetables.
Sources we checked: Yates NZ: How to grow zinnia; Kings Plant Barn: Zinnia grow well guide; Kings Seeds: Zinnia range.