How to grow komatsuna
Overview
Komatsuna is a fast-growing Japanese brassica grown for its tender, dark green leaves and crisp stems. It is a cut-and-come-again crop that thrives in mild weather and can be harvested at multiple stages from baby leaf to full head.
Varieties
- Komatsuna Green — Standard variety with large, dark green leaves and thick white stems, very productive in Australian gardens.
- Komatsuna Red — Red-tinged leaves with a mild flavour, adds colour to salads and stir-fries.
- Komatsuna Summer — Bolt-resistant selection bred for warmer weather, ideal for subtropical zones.
Soil Preparation
Komatsuna prefers well-drained, fertile soil with a pH of 6.0–7.0. Add plenty of well-rotted compost or aged manure before planting to boost nitrogen. Ensure good drainage to prevent root rot in wet conditions.
Growing Guide
Sow komatsuna seed 5mm deep in well-drained soil enriched with compost. Space plants 20–30cm apart in rows 30cm apart, or thin to 15cm for baby leaf. For best results, plant in a spot that gets morning sun and afternoon shade. Keep soil consistently moist but not waterlogged, especially during warm spells.
Sowing
Sow seed directly 5mm deep, 2–3 seeds per spot, and thin to the strongest. Germination takes 4–7 days in soil 15–25°C. Direct sowing is best; transplant only if starting in punnets for cooler zones.
Care
Feed komatsuna with a balanced liquid fertiliser every 2–3 weeks during active growth. Remove yellowing or damaged leaves to improve air circulation. No pruning is needed; simply harvest leaves as they mature.
Companion Planting
Plant komatsuna with peas, beans, onions, or beets to share the bed without competing. Avoid planting after other brassicas like broccoli, cabbage, or kale to prevent soil-borne disease buildup. Good companions include dill and chamomile to deter pests.
Common Pests & Risks
Flea beetles cause small holes in leaves; control with diatomaceous earth or fine mesh netting. Aphids cluster on new growth; blast off with water or use neem oil. Caterpillars from white butterflies can be hand-picked or controlled with Bacillus thuringiensis.
Harvesting
Harvest komatsuna leaves when they are 10–15cm long, cutting outer leaves first to extend the harvest. For whole heads, cut at the base when the plant is 20–30cm tall. Regular harvesting encourages new growth and prevents bolting.
In the Kitchen
Use young leaves raw in salads or stir-fries; mature leaves and stems are excellent in soups and sautés. Store harvested leaves in a plastic bag in the fridge for up to a week. Komatsuna has a mild, sweet flavour similar to spinach but with a crisp texture.
Troubleshooting
Yellow leaves: overwatering or nitrogen deficiency — reduce water and feed with liquid seaweed. Brown leaf edges: wind or sun scorch — move to a sheltered spot or provide shade. Holes in leaves: flea beetles — use diatomaceous earth or cover with fine netting. Leggy growth: too much shade or overcrowding — thin plants and ensure 4–6 hours of sun. Bolting: heat stress — harvest early or plant in cooler months.