When to plant Radish in Subtropical Australia

Subtropical zone — applies to Brisbane, Gold Coast, Sunshine Coast, Coffs Harbour, Lismore and similar areas. Growing elsewhere? Temperate · Tropical · Cool · Arid.

Radish can be sown direct in every month of the year in the subtropical zone, making it the closest thing to an always-on crop from Coffs Harbour to the Sunshine Coast. Push seed 15 mm deep and it germinates in as little as 5–10 days, with roots ready to pull within 40–60 days. The open window hides a quality gradient, though: sowings through the mild autumn, winter and early spring produce the crispest, sweetest roots, while midsummer sowings race to seed and turn unpleasantly hot unless grown fast in part shade and picked young.

Sowing calendar — subtropical zone

Green months are your sowing window: January to December.

Growing notes

Radish is the crop to reach for whenever a subtropical bed has a gap, but the mild season and the wet season ask different things of it. From autumn through to early spring around Brisbane, it is nearly foolproof: loose soil, even moisture and thinning to 3–7 cm between plants is the entire recipe. Over the December to February wet, the picture changes — heat pushes roots to woodiness and bolting, while storm downpours after a dry spell make them split. Summer radishes are still worth growing, but sow them where they catch afternoon shade, keep the watering shallow and regular so the soil never swings between bone dry and saturated, and harvest on the young side rather than letting roots sit.

The most common failure at any time of year is hot, pithy roots, and the cause is almost always slow growth: crowded seedlings, hungry soil or erratic water stretch the crop past its best. The fix is to sow little and often — a half row every fortnight — thin ruthlessly within a week of emergence, and pull roots as soon as they reach size rather than banking them in the ground. Flea beetles can pepper the leaves with shotholes in warm weather; seedlings usually outgrow the damage if they are growing fast, which again comes back to water and thinning.

Radish at a glance

Companion planting

Grows well with

Lettuce: Classic pairing — radish harvested before lettuce needs space

Lettuce: Harvested early before lettuce needs space; radish loosens soil

Nasturtiums: Nasturtiums deter flea beetle which attacks radish

Common questions

When can I plant radishes in the subtropical zone?

Any month of the year. The mild months from autumn to early spring give the best quality roots, while summer sowings need part shade and quick harvesting.

Why are my radishes hot and woody?

Slow, stressed growth is the cause — usually heat, crowding or uneven watering. Sow small batches often, thin early, keep the water regular and pull roots as soon as they size up.

How long do radishes take to grow?

Seed germinates in as little as 5 to 10 days and roots are ready within 40 to 60 days. Harvest promptly once they reach size, as roots left in the ground turn pithy.

Why did my radishes split after rain?

A heavy downpour after a dry spell makes the roots take up water faster than the skin can stretch, which is common in the subtropical storm season. Keep soil moisture even with regular shallow watering and mulch.

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