How To Grow Zinnia Flowers From Seed

Gardeners across the world have fallen in love with Zinnia flowers and the good news is they are really easy to grow from seed!

Sowing + Germination Tips:

  • Zinnias are frost sensitive, so wait until the last frost has passed before planting.

  • Zinnias don't like being transplanted, so if you live in a warmer climate sow zinnia seeds direct where they will grow. The seeds should germinate in 3 - 7 days when the soil temp is around 21 - 29 degrees.

  • If you live in a cooler climate, you will need to start seeds in a greenhouse environment. Raising the seedlings in single celled trays at around 21-29 degrees (a heat mat can help maintain an accurate temp) may help prevent the roots becoming root bound, reducing transplant shock when transferring the seedlings into the garden. A stressful event for the seedling can cause double-flowering varieties to produce single blooms.

Planting + Harvesting Tips:

  • After six weeks of growth in the greenhouse, the seedlings are ready to venture into the outside world. Start by letting them spend 1 hour a day outside, and work up to 5 hours over a week. This is called 'hardening off'.
  • Pinch out your zinnia seedlings when they are 30cm tall (3 true sets of leaves). Pinching out means taking the top 10cm off your seedling. This will encourage stronger, taller stems and more flowers!
  • Zinnias are heat lovers, so plant in full sun with good air circulation. This will prevent them from getting powdery mildew. 
  • Space between 15 - 30cm apart (depending on the variety) and rows 30 - 45cm apart. 
  • Taller Zinnia varieties will require support. Use flower netting staked 30cm above the ground to give them the support they need.
  • When established, water the base of the plant and try not to water the leaves. They don't like to be water logged.
  • Zinnias are annuals, so when flowering, deadheading any flowers that have died will encourage more to grow! 
  • Harvest your Zinnia blooms just before they are in full bloom and the stems are stiff. You can do the "wiggle" test - if you hold the stem about 20cm below the flower and give it a little wiggle, if the stem is floppy it's not ready to harvest. If it is stiff then it's ready!
  • The blooms will last around 7 days in a vase.

Types of Zinnias:

There are 3 main types of Zinnia flowers: double, semi-double and single. 

Double - Multiple rows of petals and no visible centre

Semi-double - Multiple rows of petals with a visible centre

Single - A single row of petals with a visible centre

Note that in warmer climates, Zinnias are more likely to produce more single rather than double blooms.  

Our most loved varieties:

Queen Series including the gorgeous Queen Lime with Blush, Queen Red with Lime, and Salmon Rose Queen. The Zinnia Queen series are mostly double and semi double blooms with a small percentage of singles.

Zinderella/Cresto crested double, semi double, and some single flowers. Unique salmon/peach colour with cream-to-rose petals and a distinct dark eye. 

Frequently asked questions about growing Zinnia flowers:

How can I prevent Zinnia mould + mildew?
Make sure there is plenty of space between each plant, this will enable plenty of airflow which will reduce the chance of mildew and fungal diseases. Water at the root of the plant early in the morning and avoid over watering. Keep dead leaves well pruned and make sure they are in a bright, sunny spot in the garden.
Why are my Zinnia seedlings leggy?
If your Zinnia seedlings are leggy, they are lacking sunlight. To stop them from being leggy put the seedlings in a spot where there is plenty of sunlight.
How can I get tall stems and lots of Zinnia flowers?
Pinching out the tip of the Zinnia seedlings when they are 30cm tall will encourage stronger stems and loads more flowers. 
Why are my Zinnias not flowering?
Zinnias love sun and warmth! Make sure they are sown or planted in a full sun position will help encourage growth and flowers.
When is the best time to sow Zinnia seeds in Australia?
It is best to sow in spring to mid summer in most areas. They can also be planted over winter in warmer regions of Australia. 

Shop our Zinnia Flower Seed collection here