The short version: In September, hardy annuals such as alyssum, calendula, cornflower, Californian poppy, everlasting daisy and snapdragon can usually go straight into garden soil across most of Australia. Frost tender flowers such as zinnia, cosmos, marigold, sunflower, celosia, amaranth and portulaca are better sown direct in warm zones and started in pots undercover where frost is still about. The deciding factor is not the calendar, it is whether your last frost has passed and the soil has warmed.
Flowers are easy to file away as the pretty optional extra, the thing you get to once the beds are full of food. That is the wrong way around. In a working home garden, flowers are the workforce.
Alyssum and cosmos bring in hoverflies, whose larvae are keen aphid eaters. Sunflowers and marigolds pull bees into the same few square metres as the zucchini. And a jar of zinnias in January is a fair return on one September afternoon with a packet of seed. This is the month the roster gets hired.
Direct sow or start in pots? Frost decides
The choice comes down to one question: has your last frost passed, or is it still ahead of you? Everything else follows from that.
Seed sown into cold, wet soil sits and sulks, and a frost tender seedling that meets a cold night can be cut off at the ankles. Starting those same seeds in pots undercover buys a few weeks of growing time without the risk, so they are ready to move out once the danger has gone.
The Bureau of Meteorology frost maps give a useful average for your part of the country. Treat that as a guide rather than a promise, because frost is stubbornly local. A low corner of the yard can sit colder than the fence line does.
Hardy annuals can go straight into the ground
Hardy annuals cope with cool soil and generally shrug off a light frost, so almost everywhere in Australia they can be sown direct now.
That group includes alyssum, calendula, cornflower, Californian poppy, everlasting daisy and snapdragon. They are forgiving of an ordinary bed, they need no heated propagator, and several of them resent being shifted about. Sowing them where they are meant to grow usually gives a sturdier plant.
Calendula is worth tucking along a vegetable bed. It can flower for months, the petals are edible, and it draws in small beneficial insects that work away unseen.
Heat lovers wait for warmth, or start undercover
Zinnia, cosmos, marigold, sunflower, celosia, amaranth and portulaca are frost tender, so the rule is simple. Sow them direct in warm zones, and start them in pots undercover in cool zones until frost is done.
In Brisbane, Darwin or Alice Springs there is nothing to wait for. In Hobart, Canberra, Ballarat or Armidale, a bright windowsill or covered bench is the safer address for a few more weeks. One caveat: zinnias and sunflowers dislike root disturbance, so use deeper pots and plant them out while still small. Most of the others transplant happily enough, which makes pots a real head start rather than a compromise.
What to sow in September, zone by zone
Here is the September list by zone. Not sure which one you are in? The postcode finder on our what to sow now page will sort it out.
Cool (Hobart, Canberra, Ballarat, Armidale)
- Direct: alyssum, calendula, Californian poppy, cornflower, everlasting daisy, snapdragon.
- In pots undercover: aster, cosmos, marigold, phlox, and sunflower from late September.
Temperate (Sydney, Melbourne, Adelaide, Perth, Newcastle)
- Direct: alyssum, aster, calendula, Californian poppy, cosmos, marigold, nasturtium, petunia, phlox, salvia, snapdragon, sunflower.
- Zinnia from late September, once the nights have lifted.
- In Perth and southern WA the summer runs dry, so mulch and steady water are what carry these annuals through to autumn.
Subtropical (Brisbane, Gold Coast, Coffs Harbour)
- Direct: amaranth, aster, celosia, cosmos, marigold, nasturtium, phlox, portulaca, salvia, sunflower, zinnia.
Tropical (Darwin, Cairns, Townsville)
- Direct: celosia, marigold, portulaca, sunflower, vinca, zinnia.
Arid (Alice Springs, Broken Hill, Mildura, Kalgoorlie)
- Direct: amaranth, celosia, cosmos, marigold, nasturtium, petunia, portulaca, sunflower, zinnia.
Flowers that earn their keep twice
The best September sowings do two jobs: they feed insects and fill a vase.
For cutting, zinnia, cosmos, sunflower and snapdragon are the easy four. All of them tend to keep producing while you keep picking, which is a generous habit in a plant. A short row of zinnia seeds sown now can supply the kitchen table from midsummer onwards.
On the insect side, alyssum, cosmos, marigold and sunflower are widely recommended as bee and hoverfly plants. Hoverflies are worth encouraging, since the adults visit flowers while their larvae work through aphids. Treat that as support rather than a substitute for other pest management, because what turns up varies with the season. Our guide to what is actually in a beneficial bug mix covers which flowers do most of the pulling.
It is also worth sowing something that does not pack up in March. Salvia and everlasting daisy both behave as short lived perennials in many gardens, stretching the colour past the annuals. Everlasting daisies are Australian natives, they hold their papery bracts long after cutting, and they suit a dry, sunny corner where fussier things sulk.
A packet of seed is a small thing to hold. Scattered along the sunny end of a bed now, it becomes the part of the garden that hums by December. If you do one thing this weekend, sow a row of alyssum or calendula beside the vegetables and let the insects find it. For the months either side, our spring sowing calendar for Australia keeps the timing straight.
Frequently asked questions
Can I sow zinnia seeds in September?
In subtropical, tropical and arid zones, yes, sow them direct now. In temperate gardens, late September is usually safe once the nights have lifted. In cool zones, start them in pots undercover and plant them out after the last frost, because zinnias are frost tender.
Which September flowers are best for bees?
Alyssum, cosmos, marigold and sunflower are commonly recommended for bees and hoverflies in Australian gardens. A mix flowering across several months tends to help more than one big flush, though what visits depends on your area and season.
What flowers can I sow in Perth in September?
Perth sits in the temperate group, so alyssum, calendula, cosmos, marigold, nasturtium, salvia, snapdragon and sunflower can all be sown, with zinnia from late September. The dry summer is the thing to plan for, so mulch well and keep the water up to them.
Which flowers sown now will give me cut flowers this summer?
Zinnia, cosmos, sunflower and snapdragon are the easiest cutters to start from seed in September. They tend to flower more freely the more you pick them, so even a small sowing can produce for weeks.
Are everlasting daisies Australian natives?
Yes. Several species of everlasting or paper daisy, including Xerochrysum bracteatum and Rhodanthe chlorocephala, are native to Australia. They suit sunny, well drained spots, and the flowers hold their colour and shape once dried.