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What flower seeds to sow in August

August 4, 2025 - 6.25am

If you've been missing colour in the garden then August is the time to start sowing flower seeds to have blooms by the end of spring.

For cold regions there is still a risk of frost so ensure flower seeds that need warmth are started in a greenhouse or similar set up. Beginning seeds before the last frost means they're ready to go in the ground once the risk of frost has passed.

Growing zones in Australia are split into tropical (Darwin, Cairns, Townsville), sub-tropical (Brisbane, Coffs Harbour), temperate (Sydney, Newcastle, Wollongong, Adelaide, Perth), cool (Melbourne, Canberra, Tasmania) or arid (Alice Springs, Tamworth) areas so check where you are before sowing any seeds.

Woman gardener picks colorful zinnias in summer garden using pruner. Cut flowers harvest. Close up. Growing annual plants — Winter is nearly over which means it's time for spring planting. Getty

Carnation

Carnation seeds can be grown in all zones in August.

It is best to raise seedlings before planting into the ground or larger pots, by sowing into trays at 6mm deep in well draining soil.

Give them plenty of sun and they will germinate seven to 14 days after sowing and blooms will appear after 200 days.

Lush bush of bicolor light and dark pink Dianthus caryophyllus of Caryophyllaceae,also called carnation Doris,growing in garden,on sunny day. Selective focus ,close-up, square photo. — Carnations have a soft, delicate look to them. Getty

Cosmos

Cosmos can be grown in temperate, sub-tropical, tropical and arid zones in August.

For cool zones you can wait until September to plant in the ground or sow now inside six weeks before the last frost.

Sow seeds directly in the ground or garden bed or raise seedlings and transplant them.

Cosmos seeds should be sown 6mm deep and, if direct sown, spaced 30cm apart.

Expect germination at seven to 20 days and blooms from eight to 12 weeks.

Cosmos bipinnatus. Light pink and white flowers on a green background. — Cosmos are a happy looking flower. Getty

Marigold

Another plant that can be sown in all zones except cool, marigolds are a staple in all gardens, especially those with vegie patches for deterring pests.

There are a few options for starting marigold seeds; sowing directly, raising seedlings or scattering seeds.

Marigold seeds should be sown 5mm deep and will germinate from four to seven days.

Nasturtium

A must for any garden, nasturtiums are brilliant for luring aphids away from your precious flowers and vegies.

They can be grown in all zones except cool during August.

Sow seeds directly in the ground or raise seedlings and transplant to the garden or pots.

Seeds must be sown to a depth of 12 to 14mm and will germinate between 10 and 20 days, sometimes earlier depending on the variety.

Nasturtium - South American trailing plant with round leaves and bright orange, yellow, or red ornamental edible flowers — Nasturtiums are edible and can be added as a salad garnish. Getty Images/iStockphoto

Salvia

Gardeners living in temperate, sub-tropical and tropical zones can sow salvia seeds now but cool zones will have to wait until September.

Salvia seeds can be sown directly in the ground or garden beds or you can choose to raise seedlings and then transplant.

Seeds need to be sown 4mm deep and will germinate from seven to 14 days.

Purple perennial Salvia — Salvia add a striking feature to the garden. Getty

Snapdragon

Temperate and sub-tropical zone gardeners can sow snapdragons in August but others will have to wait until September.

Cool zone gardeners can, however, sow indoors six weeks before the last frost.

Snapdragon seeds can be direct sown, but raising seedlings might be preferred as the seeds are extremely tiny.

Light is needed for germination so place on the seed raising mix and lightly press into the soil.

Seeds should germinate from seven to 14 days.

A large area of snapdragons blossoming in the park. — Snapdragons need support as they grow but you can get dwarf varieties that don't need staking. Getty Images/iStockphoto

Poppy

This pretty flower can be sown in all zones in August, depending on what variety of poppy it is.

Also a tiny seed, you might find it easier to sow raised seedlings and transplant as long as you're careful not to disturb the roots too much. Otherwise you can direct sow in the garden or raised beds.

Germination ranges from seven to 21 days.

Orange, pink and peach flowers in the afternoon sun — Poppies are pretty flowers and last well in a vase. Getty Images/iStockphoto

Zinnia

An absolute must for flower gardeners, especially beginners, zinnias are easy to grow and look stunning in a vase.

All climate zones except cool can sow zinnias in August. Cool zones can sow zinnias inside until warm enough to plant in the ground.

While zinnias can be direct sown or raised as seedlings, direct sowing is typically preferred (in warmer zones) as they don't like their roots being disturbed. If you do raise seedlings, take care when removing from trays not to upset the roots.

Zinnias need to be sown 6mm deep and will germinate from seven to 14 days and bloom after 90 days.

Colorful zinnias in the garden. — Zinnias are the perfect flower for beginners to start growing from seed. Getty

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