Fertilising guide
How to fertilise Nasturtium officinale (Nasturtium officinale)— schedule & NPK
Also called Watercress, Common Watercress, Water Nasturtium.
More about nasturtium officinale
About Nasturtium officinale
Nasturtium officinale · also called Watercress, Common Watercress · edible
Nasturtium officinale is watercress, a fast-growing peppery salad green in the cabbage family that thrives in cool, clean, flowing freshwater. It forms trailing stems of round leaves that root readily at every node, making it easy to grow in shallow streams, troughs or even a sunny windowsill jar. Home-grown cress avoids the contamination risk of wild stands.
Growth habit: Low, sprawling aquatic perennial herb with hollow trailing stems that root at the nodes, forming dense spreading mats of round, peppery leaves in and along water.
What fertiliser nasturtium officinale actually wants — and why
Nasturtium officinale 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 nasturtium officinale: 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 nasturtium officinale, 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 nasturtium officinale:
Feed lightly but regularly for lush leaves: a balanced or nitrogen-leaning liquid feed every few weeks during active growth, or rely on rich water/compost. Avoid heavy feeding, which can taint flavour, and never use fertilisers that would contaminate water you intend to eat from. 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 nasturtium officinale 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 nasturtium officinale
Use the vegetable-feed label rate for nasturtium officinale. 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 nasturtium officinale first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the nasturtium officinale watering schedule.
Signs you are over-feeding nasturtium officinale
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for nasturtium officinale:
- 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 nasturtium officinale
- 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 nasturtium officinale care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
For container-grown nasturtium officinale, 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 nasturtium officinale
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 nasturtium officinale — frequently asked questions
What fertiliser does nasturtium officinale 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. Nasturtium officinale 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 nasturtium officinale?
Feed lightly but regularly for lush leaves: a balanced or nitrogen-leaning liquid feed every few weeks during active growth, or rely on rich water/compost. Avoid heavy feeding, which can taint flavour, and never use fertilisers that would contaminate water you intend to eat from. Feed lightly but regularly for lush leaves: a balanced or nitrogen-leaning liquid feed every few weeks during active growth, or rely on rich water/compost. Avoid heavy feeding, which can taint flavour, and never use fertilisers that would contaminate water you intend to eat from. 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 nasturtium officinale?
Use the vegetable-feed label rate for nasturtium officinale. Steady availability matters more than a strong dose — a check in growth makes leaves tough and can trigger bolting.
What does over-feeding nasturtium officinale 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 nasturtium officinale 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 nasturtium officinale?
For container-grown nasturtium officinale, 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
- Nasturtium officinale care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water nasturtium officinale — 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 5561 fertilising guides in the Growli library