Fertilising guide

How to fertilise Corn (Zea mays)— schedule & NPK

Also called sweet corn, maize, sugar corn.

About Corn

Zea mays · also called sweet corn, maize · edible

Sweet corn is a tall warm-season annual grass grown for tender sugary cobs. Plant in blocks (not rows) for wind pollination. Heavy feeder; soil must be rich. Pet-safe.

Sweet corn is a sugary mutant of Zea mays, domesticated in Mesoamerica from the wild grass teosinte; it is a warm-season annual grass with shallow, fibrous roots.

A heavy nitrogen feeder: side-dress when plants are about a foot tall (roughly one-half cup of 46-0-0 per 100 feet of row) and scratch in, then water.

Growth habit: Tall upright annual grass

Sources: extension.umn.edu, extension.uga.edu, extension.illinois.edu

What fertiliser corn actually wants — and why

Corn 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 corn: 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, 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:

High-nitrogen feed at side-dressing once 30 cm tall; balanced feed at planting. 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 corn 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

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

Signs you are over-feeding corn

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

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 corn

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

Flushing and leaching the salts

For container-grown corn, 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 corn

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 corn — frequently asked questions

What fertiliser does corn 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. Corn 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 corn?

High-nitrogen feed at side-dressing once 30 cm tall; balanced feed at planting. High-nitrogen feed at side-dressing once 30 cm tall; balanced feed at planting. 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 corn?