When to plant Kohlrabi in Cool Australia
Cool zone — applies to Hobart, Canberra, Ballarat, Orange, Armidale and similar areas. Growing elsewhere? Temperate · Subtropical · Tropical · Arid.
Sow kohlrabi direct from January to March and again from August to December, giving it the mild shoulders of the season rather than midwinter cold. Seed germinates fast, in 6–12 days, sown shallowly at 6 mm. Thin or space plants 10–20 cm apart in rows 30–40 cm apart, and this quick brassica (Brassica oleracea var. gongylodes) swells its bulb-like stem to harvest in just 55–70 days. In cool gardens around Hobart, Canberra and Ballarat, the frost-hardy plants handle cold snaps well, and successive small sowings keep tender, mild bulbs coming.
Sowing calendar — cool zone
Green months are your sowing window: August to March.
Growing notes
Kohlrabi is a fast, hardy brassica that rewards little-and-often sowing rather than one big planting. In the cool zone it copes with frost and does its best growing in the milder ends of the season, when steady moisture and cool days keep the swollen stems crisp and sweet. It is quicker and less demanding than cabbages or broccoli, making it a good confidence-builder in short cool-climate windows.
The most common failure is woody, split or bolted bulbs. Kohlrabi that is checked by dry soil, then flooded with water, splits; left too long or stressed by heat it turns fibrous and tough; and plants that sit through a cold snap after early spring sowing can bolt to seed. The fix is even watering, harvesting young at around golf-ball to tennis-ball size, and sowing in short successions so you always have tender bulbs ready rather than a glut going woody.
As a brassica, kohlrabi is still a target for common brassica pests. Cabbage white caterpillars, aphids and slugs all take an interest, and in exposed cool gardens flea beetle can pepper the leaves. Cover young plants with fine exclusion netting to keep butterflies off, and keep the bed weed-free and evenly moist for the fastest, mildest crop.
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
- Why is my kohlrabi woody and tough?
- Woodiness comes from bulbs left too long or stressed by irregular watering and heat. Harvest young, at roughly golf-ball to tennis-ball size, keep the soil evenly moist, and sow in short successions so you catch each crop while it is still tender.
- How long does kohlrabi take to grow?
- It is quick, maturing in about 55–70 days from a direct sowing that germinates in 6–12 days. This speed makes it well suited to the short mild windows of cool gardens around Canberra or Ballarat.
- Can kohlrabi handle frost?
- Yes, it is frost-hardy and grows well in the cooler parts of the season. Avoid sowing so early that seedlings sit through a hard cold snap, though, as that can trigger bolting once warmth returns.
- Do I need to protect kohlrabi from cabbage moth?
- It helps. As a brassica, kohlrabi attracts cabbage white butterflies whose caterpillars chew the leaves. Fine exclusion netting over young plants keeps the butterflies from laying and spares you a caterpillar problem.
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