Fertilising guide

How to fertilise Red Cabbage (Brassica oleracea var. capitata f. rubra 'Red Drumhead')— schedule & NPK

Also called red cabbage, purple cabbage.

More about red cabbage

About Red Cabbage

Brassica oleracea var. capitata f. rubra 'Red Drumhead' · also called red cabbage, purple cabbage · edible

Red cabbage is a firm-headed cabbage with dense, deep-purple, anthocyanin-rich leaves storing well after harvest. It needs a long season in full sun and firm, fertile, alkaline-leaning soil with steady moisture. Net against cabbage pests, feed generously, and harvest the solid heads in autumn; many keep for weeks in cool storage.

Growth habit: Biennial grown as an annual; large outer leaves wrapping tightly into a solid, rounded, deep-purple head on a short stem.

Watch for — Cabbage root fly: Root-feeding larvae wilt and kill transplants. Use brassica stem collars, net the bed against the egg-laying flies, and rotate brassicas year to year.

What fertiliser red cabbage actually wants — and why

Red Cabbage 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 red cabbage: 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 red cabbage, 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 red cabbage:

A heavy feeder over a long season. Base-dress with compost or balanced fertiliser and side-dress with nitrogen once or twice during leafy growth. Reduce nitrogen as heads firm to keep them dense and storable rather than soft. 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 red cabbage 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 red cabbage

Use the vegetable-feed label rate for red cabbage. 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 red cabbage first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the red cabbage watering schedule.

Signs you are over-feeding red cabbage

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

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 red cabbage

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 red cabbage care brief covers soil, humidity and the common problems for this species.

Flushing and leaching the salts

For container-grown red cabbage, 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 red cabbage

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 red cabbage — frequently asked questions

What fertiliser does red cabbage 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. Red Cabbage 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 red cabbage?

A heavy feeder over a long season. Base-dress with compost or balanced fertiliser and side-dress with nitrogen once or twice during leafy growth. Reduce nitrogen as heads firm to keep them dense and storable rather than soft. A heavy feeder over a long season. Base-dress with compost or balanced fertiliser and side-dress with nitrogen once or twice during leafy growth. Reduce nitrogen as heads firm to keep them dense and storable rather than soft. 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 red cabbage?