When to plant Marigold in Temperate Australia

Temperate zone — applies to Sydney, Melbourne, Adelaide, Perth, Newcastle and similar areas. Growing elsewhere? Cool · Subtropical · Tropical · Arid.

Sow marigold direct from July through to January, using the run of months July, August, September, October, November, December and January to keep colour coming through the warm season. Set the seed 5–8 mm deep in a sunny bed and it will germinate quickly, in just 5–10 days, with flowers arriving in a fast 50–70 days. Space plants 20–30 cm apart, with rows about 30 cm apart. In Melbourne, Adelaide and Sydney these cheerful French marigolds double as pest deterrents, so many gardeners tuck them among tomatoes, beans and brassicas as well as growing them for their own long-lasting orange and gold blooms.

Sowing calendar — temperate zone

Green months are your sowing window: July to January.

Growing notes

Marigold is one of the easiest flowers to grow in a temperate garden and a genuine workhorse in the vegetable patch. Because it is frost tender, hold the main sowings for the frost-free stretch; the calendar's spread from July to January lets you start under a little protection late winter, then sow successionally into summer. Fast 5–10 day germination means you see results almost immediately.

The most common failure is powdery mildew and grey mould in a wet, still spell, which is not unusual in a humid Sydney or coastal summer. The fix is airflow and water discipline: honour the 20–30 cm spacing, water at soil level rather than over the foliage, and pull any mould-spotted lower leaves promptly.

Marigolds earn their keep as companions. Their root secretions are widely used to suppress root-knot nematodes in the soil, which is why gardeners interplant them with tomatoes; alongside basil they make a potent pest-repelling pair. They also help deter whitefly around tomatoes, Mexican bean beetle near bush beans, and cabbage moth and aphids around broccoli and cabbage. Deadhead regularly to keep flowering strong, and they will bloom right through to autumn. In hot Adelaide summers a little afternoon shade keeps the colour from bleaching.

Marigold at a glance

Companion planting

Grows well with

Tomatoes: Root secretions repel nematodes; deters whitefly

Basil: Together a potent natural pest repellant

Tomatoes: Root exudates suppress root-knot nematodes in soil

Common questions

When can I sow marigolds in Melbourne?

Sow from July through to January, starting the earliest sowings with a little protection while frost is still possible. Once the weather warms you can sow straight into the garden every few weeks for continuous flowers into autumn.

Do marigolds really keep pests away from tomatoes?

Yes, marigold root secretions help suppress root-knot nematodes in the soil, which is why they are a classic tomato companion. They also help deter whitefly, and paired with basil they make a strong general pest repellent.

Why do my marigolds get mouldy?

In humid or wet weather marigolds are prone to powdery mildew and grey mould, especially if crowded. Space plants 20–30 cm apart for airflow, water at the base rather than over the leaves, and remove affected foliage as soon as you see it.

How long do marigolds take to flower?

They are quick, germinating in 5–10 days and flowering in about 50–70 days from sowing. Regular deadheading keeps them blooming right through the warm months.

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