When should I plant marigolds in tropical Australia?

You can sow almost year-round, but the drier months from July to December and again in January to February give the strongest results. The heavy wet-season monsoon rots the flowers, so avoid your main sowings then.

Do marigolds really keep nematodes away from tomatoes?

Yes, marigold roots release compounds that suppress root-knot nematodes in the soil, which is why they are a classic companion for tomatoes. They also help deter whitefly, and planting them among brassicas discourages cabbage moth and aphids.

Why are my marigold flowers going brown and mushy?

That is usually flower rot from wet-season humidity, especially on dense double blooms that trap water. Choose single-flowered types, space plants for airflow, deadhead often and water at the base rather than over the flowers.

How long do marigolds take to flower from seed?

They germinate in 5 to 10 days and reach flowering size in 50 to 70 days, making them one of the fastest flowers to grow from seed. Sow direct 5 to 8 mm deep and thin to 20 to 30 cm apart.

When to plant Marigold in Tropical Australia

Sow marigold in tropical Australia from July to February. Method: raise seedlings,sow direct. Seeds germinate in 5-10 days, with harvest roughly 50-70 days after sowing.

Tropical zone — applies to Darwin, Cairns, Townsville, Broome, Mackay and similar areas. Growing elsewhere? Temperate · Cool · Subtropical · Arid.

Sow marigolds direct almost year-round in the tropics, with the best windows falling in January and February and again from July through to December. Drop seed 5 to 8 mm deep straight into warm soil, and it germinates fast, in just 5 to 10 days, reaching flowering size in 50 to 70 days. Space plants 20 to 30 cm apart with rows 30 cm apart in full sun. Frost tender by nature, marigolds have no frost to fear in Darwin, Cairns or Townsville, so your real limit is the wet season: the heaviest monsoon months can rot the flowers, making the drier stretch of the year the most productive.

Sowing calendar — tropical zone

Green months are your sowing window: July to February.

Growing notes

Marigolds are one of the easiest and most useful flowers for a tropical garden. They grow quickly from direct-sown seed, ask for little beyond sun and drainage, and their roots exude compounds that suppress root-knot nematodes, which is why they are so often planted alongside tomatoes and among brassicas like broccoli and cabbage. Paired with basil they make a potent pest-repelling combination, and a scatter through the vegetable patch earns its keep.

Grow them in full sun in free-draining soil. They tolerate poor ground and actually flower better when not overfed, as rich beds push leaf at the expense of blooms.

The main failure mode in the tropics is flower rot during the wet. In the humid monsoon months around Cairns and Darwin, the dense double blooms hold water, go brown and mushy, and grey mould spreads through the plant. The fix is to lean on the drier windows for your main sowings, choose single-flowered or smaller French types that shed water more easily, space plants for airflow, and deadhead spent flowers promptly so rot has nowhere to take hold. Water at the base rather than over the heads, and the plants will keep flowering for months.

Marigold at a glance

Sowing depth	5-8 mm
Plant spacing	20-30 cm
Row spacing	30 cm
Germination	5-10 days
Days to maturity	50-70 days
Frost tolerance	Frost Tender
Method	Raise Seedlings,Sow Direct

Companion planting

Grows well with

Tomatoes Basil Tomatoes Bean (Bush)Broccoli Cabbage Broccoli Cabbage Cauliflower Kale Bean (Bush)Cucumber Potato Pumpkin Zucchini Strawberries Eggplant Capsicum

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 should I plant marigolds in tropical Australia?: You can sow almost year-round, but the drier months from July to December and again in January to February give the strongest results. The heavy wet-season monsoon rots the flowers, so avoid your main sowings then.
Do marigolds really keep nematodes away from tomatoes?: Yes, marigold roots release compounds that suppress root-knot nematodes in the soil, which is why they are a classic companion for tomatoes. They also help deter whitefly, and planting them among brassicas discourages cabbage moth and aphids.
Why are my marigold flowers going brown and mushy?: That is usually flower rot from wet-season humidity, especially on dense double blooms that trap water. Choose single-flowered types, space plants for airflow, deadhead often and water at the base rather than over the flowers.
How long do marigolds take to flower from seed?: They germinate in 5 to 10 days and reach flowering size in 50 to 70 days, making them one of the fastest flowers to grow from seed. Sow direct 5 to 8 mm deep and thin to 20 to 30 cm apart.

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