How to Grow Komatsunas UK

When to Plant Komatsunas in the UK

When to plant komatsunas in the UK: in Southern England, sow mid March to late August. Find your area in the table below.

Quick Facts

At a Glance

Soil & Growing Conditions

Water: moisture-retentive, well-draining (MorningChores)

Growth Stages

Harvest & Storage

When to pick: Matures in 30-40 days; harvest leaves at any stage. Cut with shears or a sharp knife leaving at least 2 inches of stem so the plant regenerates -- usually at least two cuttings are possible. Pluck any flowers to maintain productivity (MorningChores, Seedy Farm).

Diseases

Pests

Komatsuna, Leaf to Table

Smooth, not curled or serrated

Komatsuna's leaves are smooth and spinach-like, distinct from the serrated leaves of Mizuna or the flat rosette of Tatsoi -- both grown from the same parent species, Brassica rapa.

Also known as Edo-na

This bunch is labelled Edo-na, a regional Japanese name for a komatsuna type traditionally grown around Tokyo and Chiba prefecture.

A supermarket staple in Japan

Komatsuna is sold year-round in Japanese supermarkets, reflecting how quickly it grows -- most varieties mature in just 30-40 days from sowing.

Cooked, not just raw

Named for the Komatsukawa area of Tokyo, komatsuna is a everyday side dish across Japanese cooking -- shown here lightly cooked alongside yellowtail teriyaki.

A flavour between mustard, cabbage and spinach

Its flavour is often described as a cross between mustard, cabbage and spinach -- equally at home raw in a salad or simmered into a miso soup like this one.

References

1. MorningChores - Growing Komatsuna: Best Varieties, Planting Guide, Care, Problems and Harvest

   A secondary gardening reference rather than a university or horticultural authority, used as the primary source: no RHS page or university extension publication could be located for komatsuna specifically, so this well-sourced grower guide is used with that gap explicitly noted rather than left unsourced. Optimal temperature range 45-80°F; bolts in heat but can't handle a hard frost either -- some cold-tolerant hybrids tolerate below 10°F. Full sun, with afternoon shade in harsh climates. Soil pH 5.6-7.5, moisture-retentive, fertile, loamy, well-draining; nitrogen-rich fertiliser at planting, liquid feed 15-20 days after germination. Sow 1/4-1/2in deep, spaced 6in apart with 18-24in between rows; sow spring to late summer (year-round for some hybrids), every two weeks for a constant supply. Matures in 30-40 days; harvest leaves at any stage, the plant regenerates for continuous picking; pluck flowers to maintain productivity. PESTS: flea beetles, cabbage loopers, aphids. DISEASES: leaf spot, downy mildew (grey fluff on leaves, treat with organic fungicide and improve spacing for airflow), black leg.

2. Seedy Farm - Grow Komatsuna (Japanese Mustard Spinach) for a Fast, Year-Round Harvest

   A secondary gardening reference rather than a university or horticultural authority, used only for sowing succession and harvest-cut detail not covered above, not contradicted by it. Direct sow in shallow furrows 0.5-1cm deep, rows 15-20cm apart in a garden bed or 10-15cm in a planter. Thin to 4in (10cm) apart for baby leaves used like spinach, or 8in (20cm) for mature plants. Harvest with shears or a sharp knife, slicing outer leaves away as needed, leaving at least 2 inches of stem above ground so the plant continues producing; usually at least two cuttings possible before the plant is spent.

3. Useful Temperate Plants - Brassica rapa subsp. pekinensis

   Mirrors FAO Ecocrop. Fetched and parsed directly for the numeric soil pH range.

3 independent sources are cited for this crop. Where they disagree - soil pH is the clearest case - every figure is preserved rather than averaged into false precision.