Fertilising guide

How to fertilise Corn Salad (Valerianella locusta)— schedule & NPK

Also called Corn Salad, Lamb's Lettuce, Mâche, Field Salad.

More about corn salad

About Corn Salad

Valerianella locusta · also called Corn Salad, Lamb's Lettuce · edible

Corn salad (mâche) is a cool-season salad green with mild, nutty-flavoured rosette leaves harvested baby or mature. Extremely cold-hardy, it thrives in autumn, winter, and early spring when most salad crops fail. Quick to mature at 45–60 days, it self-seeds freely and is a staple of year-round salad growing in temperate UK and US climates.

Growth habit: Low-growing rosette-forming annual or overwintering biennial. Leaves spatula-shaped, mid-green. Tiny pale blue flowers when bolted in spring.

What fertiliser corn salad actually wants — and why

Corn Salad feeds in two distinct phases — balanced to build the plant, then high-potassium the moment flowering starts to set and fill a heavy crop.

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 corn salad: 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 corn salad, 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 corn salad:

A single application of balanced general fertiliser or well-rotted compost incorporated before sowing is sufficient. Heavy feeding promotes sappy growth susceptible to mould in cold, damp winters. No feeding needed once the crop is established. So: a balanced feed or compost at planting, then a high-potash liquid every 1-2 weeks from first flower through harvest across the main season (spring through early autumn).

The dormant-season rule matters more than the exact interval: skip feeding entirely when corn salad 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 corn salad

Follow the crop-feed label rate for corn salad — these are calibrated for hungry vegetables. Consistency through fruiting matters more than strength; erratic feeding causes problems like blossom-end rot.

Feeding always goes onto already-damp soil, never dry roots — water corn salad first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the corn salad watering schedule.

Signs you are over-feeding corn salad

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

Vigorous dark-green leafy growth but few flowers or fruit (excess nitrogen).
Lush foliage hiding the crop; soft growth prone to pests and disease.
Salt crust on the soil and scorched leaf edges in containers.

Signs you are under-feeding corn salad

Pale, yellowing lower leaves and stunted growth.
Small fruit, poor set, and a quickly exhausted plant.
Blossom-end rot and weak cropping from erratic or insufficient feeding.

If the symptoms point at watering, light or roots rather than nutrition, the full corn salad care brief covers soil, humidity and the common problems for this species.

Flushing and leaching the salts

In containers, fertiliser salts build up fast — water corn salad thoroughly so excess drains from the base each time, and flush pots with plain water every few weeks to prevent a damaging salt build-up.

Organic vs synthetic feeds for corn salad

Organic options

Garden compost or well-rotted manure dug in before planting, plus a liquid comfrey or seaweed feed once fruiting starts. UK: comfrey feed or organic Tomorite; US: Espoma Tomato-tone or Neptune's Harvest. Builds soil and feeds in one.

Synthetic / liquid feeds

A balanced feed at planting then a high-potash tomato feed in fruiting — UK: Growmore at planting then Tomorite (Levington) or Phostrogen; US: a balanced 10-10-10 then Miracle-Gro Tomato or a bloom booster.

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 corn salad — frequently asked questions

What fertiliser does corn salad need?

Balanced (even N-P-K) at planting for roots and frame, then switch to a high-potassium ("high-potash") tomato-style feed once the first flowers open — potassium is what sizes and ripens fruit, not nitrogen. Corn Salad feeds in two distinct phases — balanced to build the plant, then high-potassium the moment flowering starts to set and fill a heavy crop.

How often should I feed corn salad?

A single application of balanced general fertiliser or well-rotted compost incorporated before sowing is sufficient. Heavy feeding promotes sappy growth susceptible to mould in cold, damp winters. No feeding needed once the crop is established. A single application of balanced general fertiliser or well-rotted compost incorporated before sowing is sufficient. Heavy feeding promotes sappy growth susceptible to mould in cold, damp winters. No feeding needed once the crop is established. So: a balanced feed or compost at planting, then a high-potash liquid every 1-2 weeks from first flower through harvest across the main season (spring through early autumn).

What strength of feed for corn salad?

What does over-feeding corn salad look like?

Vigorous dark-green leafy growth but few flowers or fruit (excess nitrogen). Lush foliage hiding the crop; soft growth prone to pests and disease. Salt crust on the soil and scorched leaf edges in containers. Staying on a high-nitrogen feed once corn salad starts flowering is the classic error — you get a huge leafy plant and a disappointing crop. Switch to high-potash the moment flowers appear.

Should I flush the soil of corn salad?