Fertilising guide
How to fertilise Loose-leaf Lettuce (Lactuca sativa var. crispa)— schedule & NPK
Also called Loose-leaf Lettuce, Leaf Lettuce, Cutting Lettuce.
More about loose-leaf lettuce
About Loose-leaf Lettuce
Lactuca sativa var. crispa · also called Loose-leaf Lettuce, Leaf Lettuce · edible
A fast-maturing cool-season annual producing loose, ruffled leaves harvested outer-leaf by outer-leaf from spring or autumn sowings. Prefers consistent moisture and full sun with afternoon shade in warm spells. Bolts quickly in heat, so time plantings to avoid midsummer. Ready to pick in as few as 30–45 days from sowing.
Growth habit: Upright rosette of loose, ruffled or frilled leaves; no tight head forms
Watch for — Tip burn: Brown leaf margins caused by calcium deficiency or rapid temperature swings rather than lack of soil calcium. Ensure even watering and avoid large fluctuations in day/night temperatures.
What fertiliser loose-leaf lettuce actually wants — and why
Loose-leaf Lettuce 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 loose-leaf lettuce: 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 loose-leaf lettuce, 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 loose-leaf lettuce:
Apply a balanced liquid feed (e.g. 10-10-10) every 2–3 weeks during active growth. High nitrogen encourages leafy growth; avoid overfeeding as it can cause soft, rot-prone leaves. 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 loose-leaf lettuce 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 loose-leaf lettuce
Use the vegetable-feed label rate for loose-leaf lettuce. 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 loose-leaf lettuce first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the loose-leaf lettuce watering schedule.
Signs you are over-feeding loose-leaf lettuce
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for loose-leaf lettuce:
- 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 loose-leaf lettuce
- 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 loose-leaf lettuce care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
For container-grown loose-leaf lettuce, 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 loose-leaf lettuce
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 loose-leaf lettuce — frequently asked questions
What fertiliser does loose-leaf lettuce 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. Loose-leaf Lettuce 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 loose-leaf lettuce?
Apply a balanced liquid feed (e.g. 10-10-10) every 2–3 weeks during active growth. High nitrogen encourages leafy growth; avoid overfeeding as it can cause soft, rot-prone leaves. Apply a balanced liquid feed (e.g. 10-10-10) every 2–3 weeks during active growth. High nitrogen encourages leafy growth; avoid overfeeding as it can cause soft, rot-prone leaves. 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 loose-leaf lettuce?
Use the vegetable-feed label rate for loose-leaf lettuce. Steady availability matters more than a strong dose — a check in growth makes leaves tough and can trigger bolting.
What does over-feeding loose-leaf lettuce 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 loose-leaf lettuce 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 loose-leaf lettuce?
For container-grown loose-leaf lettuce, 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
- Loose-leaf Lettuce care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water loose-leaf lettuce — 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 agave tequilana
- How to fertilise konjac
- How to fertilise elephant foot yam
- All 6887 fertilising guides in the Growli library