How to Grow Kohlrabi
Brassica oleracea var. gongylodes
Kohlrabi is a quick, cool-season brassica for full sun and moist, fertile, free-draining soil. Sow little-and-often from spring to late summer. Transplant promptly and keep growth even to prevent woody bulbs. Water regularly and mulch to retain moisture. Harvest when tennis-ball sized (or smaller for extra tenderness). Protect from flea beetle and caterpillars with fine mesh. Space closely for baby bulbs or wider for larger ones.
In your Leaftide garden - Hardiness
- Hardy
- Season
- Cool Season
- Harvest
- Single Harvest
- Spacing
- 20 cm
- Height
- 40 cm
- Sow depth
- 0.5 cm
- Min. soil temperature
- 6°C+
- Start from
- Seed
- Light
- Full sun to part shade
- Water
- Moderate
When to Start
Direct sow outdoors as soon as soil reaches 6°C — typically early to mid spring. Can also be started indoors 4 weeks earlier for a head start.
Don't know your frost date? Find it here →
Growth Stages
Approximate days from start
Care Essentials
- Light balanced feed at sowing. Needs consistent moisture.
- Quick-growing (8–10 weeks). Mild, sweet flavour — eat raw or cooked. Purple varieties are more ornamental.
Growing Conditions
- Min. soil temperature
- 6°C+
- Germination temperature
- 15–25°C
- Sow indoors
- —
- Transplant out
- —
- First harvest
- —
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Spacing & Planting
| Plant spacing | 20 cm |
| Row spacing | 30 cm |
| Sow depth | 0.5 cm |
| Mature height | 40 cm |
| Mature spread | 30 cm |
Fast crop; keep growing steadily to avoid woody bulbs.
Pests & Diseases
Pest Flea Beetle
Identification: Tiny round shot-holes peppered across leaves, small shiny black beetles that jump when disturbed
- Cover with fine insect mesh immediately after sowing or planting
- Water regularly to encourage fast growth through vulnerable stage
- Sticky traps placed near plants
- Pyrethrum-based spray as a last resort
Pest Cabbage Root Fly
Identification: Wilting plants despite adequate watering, white maggots around roots when lifted
- Brassica collars around stems at planting to prevent egg-laying
- Fine insect mesh over the crop
- Companion plant with strong-scented herbs
- No effective chemical treatments available to home gardeners
Pest Cabbage White Caterpillars
Identification: Large ragged holes in leaves, green or yellow-black caterpillars visible, clusters of yellow eggs on leaf undersides
- Cover with insect mesh from planting
- Hand-pick caterpillars and eggs regularly
- Bacillus thuringiensis (Bt) spray
- Limited options for edible crops
Disease Clubroot Plasmodiophora brassicae
Symptoms: Stunted growth, wilting in warm weather despite moist soil, swollen and distorted roots
Treatment: No cure once established. Remove and destroy affected plants. Do not compost.
Prevention: Lime soil to pH 7.0-7.5. Practice strict 4-year brassica rotation. Improve drainage. Start plants in modules with clean compost.
Disease Downy Mildew Hyaloperonospora parasitica
Symptoms: Yellow patches on upper leaf surfaces with grey-white fuzzy growth underneath
Treatment: Remove affected leaves promptly. Improve air circulation.
Prevention: Space plants well for airflow. Avoid overhead watering. Water in the morning so foliage dries quickly.
Disease White Blister Albugo candida
Symptoms: Glossy white pustules on leaf undersides. Distortion of leaves and stems.
Treatment: Remove and destroy affected leaves.
Prevention: Rotate crops. Ensure good air circulation.
Growing Conditions
| Min. soil temperature | 6°C |
| Germination temperature | 15–25°C |
| Base growth temperature | 4°C |
| Min. daylength to start | 9h |
| Photoperiod sensitivity | day neutral |
Frequently Asked Questions
- How far apart should I plant Kohlrabi?
- Plant Kohlrabi 20cm apart with 30cm between rows.
- When can I harvest Kohlrabi?
- Kohlrabi is ready to harvest approximately 35 days after transplanting.
- Is Kohlrabi frost hardy?
- Kohlrabi is classified as Hardy.