Fertilising guide

How to fertilise Lettuce (Lactuca sativa)— schedule & NPK

Also called leaf lettuce, head lettuce, cos lettuce.

About Lettuce

Lactuca sativa · also called leaf lettuce, head lettuce · edible

Lettuce is a cool-season leafy crop that bolts in heat and rots in waterlogged soil but is otherwise nearly fool-proof. Best grown in spring and autumn or, in hot summers, in afternoon shade. Pet-safe by ASPCA standards.

Lactuca sativa was domesticated in the Mediterranean region of southern Europe, eastern Asia and northern Africa; it is a cool-season crop that bolts when summer heat and warm nights arrive.

Responds to fertile, organic-rich soil for fast leaf production; organic mulch moderates soil temperature to sustain quality in marginal weather.

Growth habit: Annual rosette

Watch for — Yellow leaves: Heat stress, nutrient depletion, or downy mildew.

Sources: extension.umn.edu, content.ces.ncsu.edu, extension.illinois.edu

What fertiliser lettuce actually wants — and why

Lettuce 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 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 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 lettuce:

Compost at planting is usually enough; a half-strength balanced feed every 3 weeks for cut-and-come-again types. 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 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 lettuce

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

Signs you are over-feeding lettuce

Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for 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 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 lettuce care brief covers soil, humidity and the common problems for this species.

Flushing and leaching the salts

For container-grown 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 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 lettuce — frequently asked questions

What fertiliser does 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. 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 lettuce?

Compost at planting is usually enough; a half-strength balanced feed every 3 weeks for cut-and-come-again types. Compost at planting is usually enough; a half-strength balanced feed every 3 weeks for cut-and-come-again types. 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 lettuce?