Plant colourful summer zinnias

Looking for an easygoing plant that doesn’t mind the heat of summer and does equally well in sprawling gardens or containers on balconies? Zinnias are the answer. 

You can mix up different varieties of zinnias for a colourful garden.
Photo: Melanie Kercheval

Zinnias come in annual, perennial and shrub varieties and are related to sunflowers and daisies. One of the first cut flower varieties I grew from seed, I fell in love with their robust cheer in the garden and with their versatility as a cut flower. They come in a diverse range of colours and shapes, including double and semi-double forms, and will bloom throughout summer. Zinnias look terrific mass-planted and also do well in pots.

Planting and care 

  •  Your zinnias prefer somewhere sunny and free draining with additional compost added to the soil. They hate root disturbance and do best when sown directly after the last frost. But they also dislike cold, so in the cool climate here in Victoria, we tend to start our zinnia in punnets and plant out with our other annuals in early November. The transplanted ones tend to get so grumpy at being moved that they stall long enough for the direct-sown ones to catch up. 
  •  Seed can be sown from mid-spring well into summer, or purchase seedlings. Plant seeds 20cm apart, then cover with 5mm of fine soil and keep moist until they shoot. Zinnias should sprout within 10 days. 
  •  If you’re planting out from a punnet or pot, dig a large hole and plant the zinnia so the soil level is at the same level as the top of the root ball. Pat down and water in well. 
  •  Some commercial growers recommend adding flower netting at 30cm to support them. However, we grow our zinnias without netting and they do just fine. 
  •  To promote more vigorous growth, pinch your zinnia when it’s about 30cm tall. “Pinching” means taking the top few centimetres off your plant. Make sure to make the cut with clean, sharp snips, just above an existing set of leaves. 

You can get Eliza's full article on planting summer flowers, including more about zinnias, rudbeckia, salvia and cornflowers, by purchasing a copy of OG Issue 129!

By: Eliza Henry-Jones

First published: November 2021

Related topics

Gardening Basics, Flowers, zinnias, annual, perennial, shrub, Issue 129 -- November/December 2021, Ornamentals