How to grow Cosmos from seeds + Our Top 5 Most Loved Varieties

Cosmos Seedling

Flower farms and backyard cut flower gardens are going crazy for cosmos. Heres some simple tips to grow the your best cosmos from seed! 

Cosmos are super easy flower to grow and will bloom 12 weeks after you sow! Best planted from Spring to Summer.

  • Once frosts have passed, start seeds off indoors in a greenhouse like environment for the first 6 weeks. They will germinate at around 7 days. After the first 6 weeks they can be transplanted into the garden. When ready to be transplanted into the garden then hardening them off over a 5-7 days will prevent any transplant shock. Leaving the seedlings in punnets outside for a few hours per day. 
  • Alternatively cosmos can be sown direct after frost have passed and then thinned out to 20-30cm apart.
  • Pinch out your cosmos seedlings when the are 30cm tall (3 true sets of leaves). Pinching out means taking the top 10cm off your seedling. This will encourage a bushier foliage, and more flowers! 
  • Taller varieties such as the sensation may need staking for support.
  • Cosmos like full sun and well draining soil. 
  • Deadheading your cosmos will keep a continues supply of blooms to be enjoyed over Spring and Summer. 
  • Cosmos is an annual flower but the seeds can be saved for next year by letting the flower die back and the petals will fall off - the seeds will then form. They will be ready to harvest once the head has completely opened and brown and dry. They need to be 100% dry before storing, they can then be labelled and put in an airtight container, ready to be sown again next year!

Our Top 5 most loved Cosmos Varieties:

Cosmos Cupcake a new variety that comes in blush, mixed and white. Cosmos cupcakes is as showy as Double Click with lighter-weight blooms held upright on stems. The light-coloured, finely pleated blooms float above the foliage, reminding us of Degas' paintings of ballerinas. A small percentage of flowers have lovely, tufted centres.

Cosmos Double Click, Cranberry, Bi Colour Violet, Snow puff, bi colour pink and mixed. Double click series are tall plants with large, fully-double and semidouble blooms.

Cosmos Sensations, Purity White, Daydream, Candy Stripe. Cosmos Sensations are a tall dainty daisy like cosmos that make a great cutting flower.

Cosmos Seashell are a unique cone seashell shaped cosmos. 

Cosmos Xsenia is a new terracotta rose colour. Multi coloured blooms appear luminous. Multi-coloured blooms appear luminous. Petals display a lovely rose colour at the edges and flower centre with terracotta orange filling in the mid-petals. This brilliant colour fades to a warm, antique rose as blooms mature.

Frequently asked questions about growing cosmos flowers:
Why are my cosmos seedling leggy?
If your cosmos seedlings are legging this means they are lacking sunlight.
They have become legging as they are looking for light. To stop them from being leggy put the cosmos seedlings in a sunny spot where there is plenty of sunlight.
Why are my cosmos plants tall and not bushy?
Pinching out the tip of the cosmos seedlings when they are 30cm tall will encourage bushier foliage and more flowers. 
Why are my cosmos not flowering?
Cosmos love sun! Making sure they are sown or planted in a full sun position will help encourage growth and flowers.
When to sow cosmos in Australia?
Spring to mid summer in most areas and can also be planted over winter in warmer areas of Australia.