Fertilising guide
How to fertilise Curly Kale (Brassica oleracea var. sabellica 'Curly Kale')— schedule & NPK
Also called curly kale, Scots kale, common kale.
More about curly kale
About Curly Kale
Brassica oleracea var. sabellica 'Curly Kale' · also called curly kale, Scots kale · edible
Curly kale is a hardy leafy brassica with tightly ruffled, frilly leaves on an upright stem. Exceptionally cold-tolerant, it crops through autumn and winter and actually sweetens after frost. Grow in full sun in firm, fertile, alkaline-leaning soil, keep it well watered and netted against cabbage pests, and pick young leaves over a long season.
Growth habit: Upright, non-heading biennial grown as a leafy annual; a single thick stem topped with a rosette of tightly curled leaves, picked from the bottom up over many months.
Watch for — Clubroot: Soil-borne disease swelling and distorting roots, stunting plants in acidic, wet ground. Lime the soil, improve drainage, rotate brassicas, and never compost infected roots.
What fertiliser curly kale actually wants — and why
Curly Kale is grown entirely for its leaves, so nitrogen is the priority — steady, nitrogen-leaning feeding keeps it growing fast, tender and unbolted.
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.
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 curly kale: 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 curly kale, 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 curly kale:
A hungry crop. Work compost or a balanced base feed into the bed, then side-dress with nitrogen-rich fertiliser once or twice during active growth to keep leaves coming. Ease off feeding in late autumn so winter growth hardens off before hard frost. 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 curly kale 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 curly kale
Use the vegetable-feed label rate for curly kale. 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 curly kale first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the curly kale watering schedule.
Signs you are over-feeding curly kale
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for curly kale:
- 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 curly kale
- 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 curly kale care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
For container-grown curly kale, 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 curly kale
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 curly kale — frequently asked questions
What fertiliser does curly kale 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. Curly Kale 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 curly kale?
A hungry crop. Work compost or a balanced base feed into the bed, then side-dress with nitrogen-rich fertiliser once or twice during active growth to keep leaves coming. Ease off feeding in late autumn so winter growth hardens off before hard frost. A hungry crop. Work compost or a balanced base feed into the bed, then side-dress with nitrogen-rich fertiliser once or twice during active growth to keep leaves coming. Ease off feeding in late autumn so winter growth hardens off before hard frost. 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 curly kale?
Use the vegetable-feed label rate for curly kale. Steady availability matters more than a strong dose — a check in growth makes leaves tough and can trigger bolting.
What does over-feeding curly kale look like?
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. Letting curly kale run short of nitrogen mid-crop is the main mistake — growth checks, leaves toughen and brassicas/leafy greens bolt or turn bitter. Keep nitrogen steadily available.
Should I flush the soil of curly kale?
For container-grown curly kale, 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.
Keep reading
- Curly Kale care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water curly kale — the watering schedule
- The houseplant fertiliser schedule — feeding through the year
- NPK ratio explained — what the three numbers on the bottle mean
- How to fertilise tomato
- How to fertilise pepper
- How to fertilise cucumber
- All 2464 fertilising guides in the Growli library