Fertilising guide

How to fertilise Mibuna (Brassica rapa var. nipposinica 'Mibuna')— schedule & NPK

Also called mibuna, Japanese greens, Mibu greens.

More about mibuna

About Mibuna

Brassica rapa var. nipposinica 'Mibuna' · also called mibuna, Japanese greens · edible

Mibuna is a Japanese leaf brassica forming dense rosettes of slender, smooth, strap-like leaves with a mild mustardy bite. A close relative of mizuna, it is fast, cold-hardy, and reliably cut-and-come-again. It excels in cool-season and overwintered sowings, supplying salad and stir-fry greens from baby-leaf size to mature clumps.

Growth habit: Dense rosette of many narrow, rounded-tip leaves on thin stalks; regrows repeatedly after cutting, making it a heavy-yielding cut-and-come-again green.

What fertiliser mibuna actually wants — and why

Mibuna is grown entirely for its leaves, so nitrogen is the priority — steady, nitrogen-leaning feeding keeps it growing fast, tender and unbolted.

For the language behind the three numbers on the bottle — what nitrogen, phosphorus and potassium each do — see the NPK ratio explained entry. The short version for mibuna: match the feed to the job the plant is doing right now, not to a generic “plant food” on the shelf.

How often to feed mibuna, and which months

Feeding only earns its keep while the plant is in active growth and can use the nutrients — pour feed into a dormant or low-light plant and it simply builds up as root-burning salt. For mibuna:

As a leafy crop it benefits from rich soil at sowing plus a nitrogen-leaning feed: side-dress with compost or apply dilute liquid seaweed/balanced feed every 2-3 weeks during active growth. In practice: a balanced or compost-rich start, then a nitrogen side-dress or liquid feed every 3-4 weeks through the cropping period in the main season (spring through early autumn).

The dormant-season rule matters more than the exact interval: skip feeding entirely when mibuna is resting. For the wider context on indoor feeding rhythms across the seasons, the houseplant fertiliser schedule walks through the year month by month.

What strength to mix for mibuna

Use the vegetable-feed label rate for mibuna. Steady availability matters more than a strong dose — a check in growth makes leaves tough and can trigger bolting.

Feeding always goes onto already-damp soil, never dry roots — water mibuna first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the mibuna watering schedule.

Signs you are over-feeding mibuna

Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for mibuna:

Very soft, floppy, dark-green growth that attracts aphids.
Excess leafy growth at the expense of hearts/heads in cabbage and the like.
Salt crust and scorched leaf edges in containers; nitrate-heavy leaves.

Signs you are under-feeding mibuna

Pale, yellow-green leaves, oldest first, and slow growth.
Small, tough, bitter leaves and premature bolting.
Weak, stunted heads in cabbage, broccoli and cauliflower.

If the symptoms point at watering, light or roots rather than nutrition, the full mibuna care brief covers soil, humidity and the common problems for this species.

Flushing and leaching the salts

For container-grown mibuna, water until it drains freely each time and flush pots monthly with plain water to stop nitrogen salts accumulating; in the ground, good compost levels naturally buffer this.

Organic vs synthetic feeds for mibuna

Organic options

Well-rotted manure or compost dug in, plus nitrogen-rich liquid feeds like diluted chicken-manure pellets or nettle feed. UK: pelleted chicken manure or Westland; US: Espoma Garden-tone or blood meal. Steady and soil-building.

Synthetic / liquid feeds

A balanced feed at planting then a high-nitrogen liquid or granular side-dress — UK: Growmore then a nitrogen feed or Phostrogen; US: a 10-10-10 then a high-N (e.g. 21-0-0) side-dress or Miracle-Gro.

Brand names are examples, not endorsements, and UK and US ranges differ — check the label’s own NPK and dilution rate, since formulations change.

Fertilising mibuna — frequently asked questions

What fertiliser does mibuna need?

A nitrogen-leaning feed (higher first number) or compost-rich soil — nitrogen drives the fast, tender leafy growth this crop is grown for. Phosphorus and potassium matter far less here than for fruiting crops. Mibuna is grown entirely for its leaves, so nitrogen is the priority — steady, nitrogen-leaning feeding keeps it growing fast, tender and unbolted.

How often should I feed mibuna?

As a leafy crop it benefits from rich soil at sowing plus a nitrogen-leaning feed: side-dress with compost or apply dilute liquid seaweed/balanced feed every 2-3 weeks during active growth. As a leafy crop it benefits from rich soil at sowing plus a nitrogen-leaning feed: side-dress with compost or apply dilute liquid seaweed/balanced feed every 2-3 weeks during active growth. In practice: a balanced or compost-rich start, then a nitrogen side-dress or liquid feed every 3-4 weeks through the cropping period in the main season (spring through early autumn).

What strength of feed for mibuna?