How to grow Zinnia in Australia
Zinnias (Zinnia elegans) are fast, heat-loving summer annuals from Mexico with bright single, double and pompom flowers in almost every colour except blue. They are easy to grow from seed sown straight into warm soil, flower within about eight weeks, make excellent long-lasting cut flowers, and draw bees, butterflies and hoverflies into the vegie patch.
📖 Our full guide: How to Grow Zinnias in Australia
At a glance
When to sow by region
| Region | When to sow | Regional note |
|---|---|---|
| South East Queensland | September to February | |
| Northern Rivers NSW | September to February | |
| Sydney & Coastal NSW | October to January | Sow Oct to Jan into warm soil in full sun. Frost tender, and slow and mildew prone in cool weather. |
| Melbourne & Victoria | October to December | Frost tender. Sow direct Oct to Dec once the soil is warm. Flowers until the first autumn frost. |
| Adelaide & SA | September to December | Sow Sep to Dec once the soil is warm. Zinnias love a hot dry summer; water at the base to keep mildew off. |
| Perth & WA | September to December | Sow Sep to Dec once the soil is warm. Zinnias love a hot dry summer; water at the base to keep mildew off. |
| Tasmania | November and December | Sow Nov to Dec in full sun. Slow in cool summers, so a hot spot helps. |
| Canberra & ACT | November and December | Frost tender. Sow Nov to Dec after the last frost in early November; flowers until the first autumn frost. |
| North Queensland | April to October | Sow Apr to Oct for dry season colour. Wet season humidity brings mildew and rots the seedlings. |
| Darwin & Top End | April to October | Sow Apr to Oct for dry season colour. Wet season humidity brings mildew and rots the seedlings. |
Where to plant
Zinnias need full sun, warmth and fertile, well-drained soil. They love hot, dry summers and many varieties are quite drought tolerant once established. Give them shelter from strong wind, which flattens tall types.
They are frost tender and sulk in cool, damp weather, which also brings powdery mildew. Good air flow between plants helps.
- South East Queensland and the Northern Rivers: sow from September to February.
- Sydney: sow from October to January into warm soil.
- Adelaide and Perth: sow from September to December once the soil is warm. Zinnias revel in the hot, dry summers.
- Melbourne: sow from October to December once the soil is warm; they flower until the first autumn frost.
- Hobart and Canberra: sow in November and December after the last frost, in the hottest spot you have.
- North Queensland and Darwin: sow from April to October for dry season colour, as wet season humidity brings mildew and rots seedlings.
Choosing a variety
- Tall, large-flowered types, such as dahlia-flowered mixes and Benary's Giant, grow to about 90 cm with long stems for cutting.
- Dwarf and pompom types, such as Lilliput, stay compact for edging and pots.
- Newer mildew-resistant varieties are worth choosing in humid areas.
How to plant
- Wait for warm soil and settled weather after frost. Zinnias sown into cold soil are slow and prone to rot.
- Sow seed directly where it is to grow, about 0.5 cm deep, and firm it down.
- Keep the soil moist. Seedlings appear in about five to seven days.
- Thin to about 20 to 30 cm apart, or closer for dwarf types, to give each plant air.
Watering and feeding
Water regularly at the base of the plants, not over the leaves, which invites powdery mildew. Mulch to hold moisture through summer.
Feed every one to two weeks with a liquid flower fertiliser, or more lightly in rich soil, for steady flowering.
Pruning and care through the year
- Pinch out the first flower bud or the growing tip when plants are young, to make them branch and carry more flowers.
- Deadhead spent flowers, or keep cutting them for the vase, to keep new ones coming all season.
- Stake tall varieties in windy spots.
Cutting flowers
Cut zinnias in the cool of the morning when the flowers are fully open. A simple test is to hold the stem about 20 cm below the flower and shake it gently: if the stem stays upright, the flower is ready; if it droops, wait a day or two. Strip the lower leaves and put them straight into water. They last about a week or more in a vase, and the more you cut, the more they flower.
Growing in pots
Dwarf and medium zinnias grow well in a pot at least 20 cm wide and deep with a quality potting mix, in full sun. Water regularly and feed every couple of weeks.
Saving seed
Leave a few of the best flowers to dry on the plant until the heads turn brown and papery. Pull them apart and keep the arrow-shaped seeds that have a plump centre. Seed from hybrids may not come true.
Companion planting
Zinnias are one of the best flowers for a summer vegie patch, bringing in bees to pollinate fruiting crops and hoverflies whose larvae eat aphids.
Good companions
- Tomato Brings pollinators and beneficial insects into the tomato bed.
- Beans A summer crop with the same warm season; zinnias draw bees to the bean flowers.
- Cucumber Cucumbers need bees to set fruit, and zinnia flowers attract them.
- Capsicum Shares the same hot, sunny bed and benefits from the beneficial insects zinnias attract.
- Marigold Another bright summer flower for the same bed that attracts beneficial insects.
Pests and diseases
Powdery mildew is the main problem with zinnias, especially in humid weather or late in the season.
Pests to watch for
- Aphids Clusters on buds and soft new growth.
- Spider mite Fine pale speckling on the leaves and webbing in hot, dry weather.
- Caterpillars Chewed petals and leaves.
Diseases to watch for
- Powdery mildew White powder on the leaves, worst in humid weather and late summer. Water at the base, space plants and choose resistant varieties.
- Alternaria leaf spot Reddish-brown spots with greyish centres on leaves and petals in wet weather.
- Bacterial leaf spot Small, angular, water-soaked spots on the leaves that turn brown, spread by water splash.
Common questions
When should I plant zinnias in Australia?
In spring and summer once the soil is warm: September to February in South East Queensland, October to January in Sydney, September to December in Adelaide and Perth, and October to December in Melbourne. In the tropics, sow from April to October. Pick your region at the top of the page for the months.
How long do zinnias take to flower?
Usually about eight weeks from sowing, and they keep flowering until autumn or the first frost if you deadhead or cut them.
Why do my zinnias have white powder on the leaves?
That is powdery mildew, the most common zinnia problem. Water at the base, space plants for air flow, and choose mildew-resistant varieties in humid areas.
Should I pinch zinnias?
Yes. Pinch out the tip or first bud on young plants to make them branch. You get more flowers on longer stems for cutting.
Are zinnias good for bees?
Yes. Single and semi-double zinnias especially attract bees, butterflies and hoverflies, which makes them a good companion in the vegie patch.
How do I know when to cut zinnias?
Hold the stem about 20 cm below the flower and give it a gentle shake. If the stem stays straight, it is ready to cut; if the flower head flops, wait a day or two.
Sources we checked: Yates: How to grow zinnias; Wikipedia: Zinnia elegans.