When to plant Kohlrabi in Tropical Australia
Tropical zone — applies to Darwin, Cairns, Townsville, Broome, Mackay and similar areas. Growing elsewhere? Temperate · Cool · Subtropical · Arid.
Sow kohlrabi direct from April to September, spacing your sowings through the cooler dry season for a steady supply. This fast brassica is one of the more tropics-friendly of its family, germinating quickly in 6–12 days and reaching harvest in just 55–70 days. Sow seed 6 mm deep, then thin plants to 10–20 cm apart with rows 30–40 cm across. Grown for its swollen, above-ground stem rather than a head, kohlrabi suits the dry months in Townsville and Mackay, where cooler nights keep the bulbs crisp and sweet rather than woody and bolt-prone.
Sowing calendar — tropical zone
Green months are your sowing window: April to September.
Growing notes
Kohlrabi earns its place in tropical gardens by being quick — a 55–70 day crop slots neatly into the dry season, dodging the humidity and heat that plague slower brassicas. Sow direct 6 mm deep from April to September, keep the seedbed moist for even germination over 6–12 days, and thin to 10–20 cm so each swollen stem has room to fatten.
The key failure mode in the tropics is bolting and woodiness. When kohlrabi hits heat stress or dries out, it rushes to flower and the edible stem turns tough and fibrous. Avoid this by sowing within the cool dry-season window, watering consistently, and harvesting promptly once bulbs reach 6–8 cm — waiting too long lets them go woody. Small and tender beats big and stringy every time.
The usual brassica pests still apply. Aphids cluster on new growth and can be hosed or squashed off, while grasshoppers and caterpillars chew the leaves. Steady moisture and a light nitrogen feed keep growth fast and leaves soft, which also helps the stems stay sweet. Because the crop is short, successive sowings every two to three weeks across the dry season give you a rolling harvest rather than a single glut, which suits Cairns and Darwin gardeners wanting fresh brassicas through the cooler months without a large, fussy planting.
Kohlrabi at a glance
| Sowing depth | 6 mm |
|---|---|
| Plant spacing | 10-20 cm |
| Row spacing | 30-40 cm |
| Germination | 6-12 days |
| Days to maturity | 55-70 days |
| Frost tolerance | Hardy |
| Method | Sow Direct |
Common questions
- When should I plant kohlrabi in the tropics?
- Sow direct from April to September, through the cooler dry season. Kohlrabi is fast at 55–70 days, so this window gives you crisp, sweet stems while avoiding the heat and humidity that cause bolting and disease.
- Why is my kohlrabi tough and woody?
- Woodiness comes from heat stress, dry conditions or leaving the bulb too long. Sow within the cool dry season, water consistently, and harvest once stems reach 6–8 cm rather than letting them grow large.
- How far apart should kohlrabi be spaced?
- Thin plants to 10–20 cm apart with rows 30–40 cm. Crowded plants produce small, competing stems, while proper spacing lets each swollen stem develop fully.
- Can you grow kohlrabi in Townsville's dry season?
- Yes. Townsville's cooler dry-season nights suit kohlrabi well, keeping the stems crisp and sweet. Make successive sowings every couple of weeks for a steady supply through the dry months.
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