Vegetable · Poaceae
Sweet Corn
Zea mays
Set it in a block, not a row, feed it well, and sweet corn crowns the late-summer garden with full, milky ears.
Full sun
Every 3–7 days
50–95°F · 10–35°C
60–100 days
Overview
Sweet corn is the plant that turns a plot into high summer. A tall grass grown for its sugary ears, it carries echoes of the Americas, where it was bred from wild grasses thousands of years ago, and it settles into the modern garden as a warm season annual almost anywhere. Give it sun, warmth, and rich ground, and a few square feet become a living backdrop and a real summer harvest at once.
What corn asks for that few vegetables do is togetherness, and that single quirk shapes how it sits in a space. It pollinates on the wind, pollen drifting from the tassels down to the silks, so a lone plant set out for looks will disappoint. Gather it into a block of several short rows and it earns its keep as a green summer screen, while the wind quietly fills every ear from butt to tip.
Corn keeps a generous appetite, and a productive patch repays the bed it is given. It wants steady water and a heavy hand with nitrogen, and it has little patience for cold soil or a cramped corner. Plan the timing and the feeding into the season and it rises fast and full, but cut corners and the harvest comes in gappy and half-filled, a quieter end to the summer than the plant promises.
Care
The short version: corn wants full sun, rich soil, and plenty of water, set into a block rather than a single row so the wind can pollinate it. Feed it generously, since corn is a heavy nitrogen feeder, and keep the bed moist once the silks appear.
Light
Corn wants full sun and nothing less, with no shade to dim it. Tall and quick to rise, it casts plenty of shade of its own, so reserve the most open, sun-washed corner of the garden for it.
Water
Hold the bed evenly moist, working toward about an inch of water a week. Moisture matters most from tasseling and silking through ear fill, when a dry spell quietly leaves you with poorly filled ears.
Soil
Give it fertile, well drained loam with plenty of organic matter dug through. A pH of 6.0 to 6.8 suits it best, and that rich ground answers the appetite a productive patch brings.
Temperature
Corn settles across a wide range, from about 50°F to 95°F (10°C to 35°C), though it needs warm soil to begin and a long warm stretch to ripen. Sown too early into cold ground, the seed rots before it ever rises.
Humidity
Ordinary outdoor air is all the humidity corn asks for, so there is no figure to chase. What shapes the harvest is the wind, the quiet hand that carries pollen from tassel to silk and rounds out the ears.
Feeding
Corn is a heavy nitrogen feeder, and a generous bed shows in the harvest. Work a balanced fertilizer in at planting, then side-dress with nitrogen once the plants stand about a foot tall and again as they tassel.
Pruning
There is nothing to prune, which keeps the patch low on upkeep. Leave the tillers that rise at the base of the stalks, since removing them adds no yield and can cost some; only smut galls or clearly diseased stalks call for the knife.
Size & spacing
Stalks rise 5 to 8 feet (150 to 250 cm) tall yet keep a narrow footprint, so plants can stand close, about 8 to 12 inches (20 to 30 cm) apart. Gather them into a block of several short rows rather than one long line, and the patch reads as a green wall across the summer garden.
When to plant
Corn keeps to the rhythm of warmth and will not stand a frost, so the season opens only when spring has truly settled. Wait for the cold to lift and the soil to reach at least 60°F (16°C), then sow the seed straight into the bed. A fresh patch every couple of weeks carries the harvest from midsummer into early fall, an easy way to keep the table supplied.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Not recommended; corn resents root disturbance and is best direct-sown
- Plant: Direct sow after the last frost once soil has warmed to at least 60°F (16°C); plant in blocks of at least 3-4 short rows rather than one long row to ensure wind pollination
- Harvest: Tassels and silks appear in mid to late summer; harvest at the milk stage, about 18-24 days after silks appear, when kernels exude milky juice when punctured and silks are brown and dry
Hardiness
USDA hardiness zones: 2–11
Temperature: down to -46°C
Troubleshooting
Most of corn's trouble gathers on the ears and the stalks, and much of it traces back to how the patch was laid out rather than to any pest. Read the early signs and the season can still be saved, or at least the ears already on the plant. Match what the garden shows you below, then step in while it still makes a difference.
Nibbled kernels and a caterpillar at the crown of the ear
A caterpillar at the crown of the ear is the corn earworm, which travels down the silk channel to feed at the very top. It rarely ruins the harvest, since the damage keeps to the first few inches; trim the tip in the kitchen and the rest of the cob arrives at the table unspoiled. A few drops of mineral oil on the silks a few days after they appear, or a light pass of Bt, spares the ears that follow.
Fix:
- Cut away the damaged tip; the rest of the ear is fine to eat
- Apply a few drops of mineral oil to silks 3-7 days after silking begins
- Treat fresh silks with Bt (Bacillus thuringiensis) or spinosad according to label directions
Uneven ears freckled with bare patches and shriveled kernels
An ear that comes to the table half empty is the signature of poor pollination, the result that follows when corn is set out as a single picturesque row the wind can never serve. A dry spell during silking only deepens the shortfall. Arrange the plot as a generous block of three or four short rows, keep the bed moist once the tassels rise, and a gentle shake of the tassels over the silks will round out a thin patch by hand.
Fix:
- Water deeply during silking and ear fill
- Hand-pollinate small plantings by shaking tassels over fresh silks
Bloated gray galls that spill a sooty black powder
Those swollen growths are common smut, a fungus that enters through small wounds and spreads through hot, dry weather, most of all in a bed run rich with nitrogen. The galls begin firm and silvery before they darken and split, scattering powdery black spores across the plot. Lift them out and bag them for the trash before they rupture, and keep them well away from the compost heap where they would only settle in.
Fix:
- Remove and destroy galls before they rupture; do not compost them
Stalks bowing over or breaking in a stiff breeze
When the tall green screen leans after a storm, look to the base before blaming the weather, since corn gives way for two separate reasons. Shallow roots in loose, unhilled soil simply lose their grip, while small entry holes ringed with sawdust-like frass reveal that a corn borer has hollowed the stalk from within. Stand the plants up again and draw soil around the base, then shred and till the spent stalks at season's end so next year's bed starts clean of the borers that would overwinter there.
Fix:
- Gently stand plants back up and hill soil around the base after storms
- Destroy crop residue after harvest to remove overwintering borers
Orange rust freckles and long, tan lesions along the leaves
Orange spots that smudge off on a fingertip are common rust, while long cigar-shaped gray-tan lesions, arriving with warm and humid spells, mark northern corn leaf blight. Late in the season neither one troubles the harvest, and a relaxed gardener can simply leave them to run their course. Tidy away the worst of the lower leaves, and choose resistant hybrids next year to keep the planting looking its best.
Fix:
- Remove heavily infected lower leaves
- Severe cases on young plants may warrant a labeled fungicide; late-season infection rarely needs treatment
Toxicity
The reassuring word first: sweet corn is safe. No part of the plant is poisonous to people, pets, or livestock, which is why it sits as easily on the dinner table as in the feed bucket. The one note for the household is the bare cob, which a dog can swallow and choke on or block its gut, so clear finished cobs away once the meal is done.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
There is no poison in this plant to worry the household cat. A nibbled leaf or a kernel that strays to the floor poses no threat from the plant itself.
Dogs None
The plant will not poison a dog, yet the spent cob is a hazard of another order entirely. A swallowed cob or a broken piece can lodge in the gut and block it, so finished cobs belong well out of a dog's reach after dinner.
Horses Safe
Grain corn is a familiar part of the feed bucket, and the plant carries nothing that would unsettle a horse.
Rabbits Safe
A rabbit may browse it without concern, though its table is best laid mostly with leafy greens and only the occasional taste of corn.
Livestock Safe
Corn has fed cattle, sheep, and goats across the generations and holds no toxin for any of them.
Birds Safe
Hens and wild birds take to the kernels with pleasure, and nothing in the plant will do them harm.
People Safe
Sweet corn is a summer fixture at the table, eaten fresh from the cob or cooked, with no part of it set aside.
Although corn is not poisonous, whole corn cobs are a serious physical hazard for dogs: swallowed cobs or cob chunks commonly cause choking or intestinal obstruction. Never give dogs cobs to chew and secure compost and trash.
Varieties
Sweet corn arrives in standard, sugary-enhanced, and supersweet types, each holding its sugar a little differently once it leaves the stalk. A few are worth knowing by name.
Silver Queen
A classic standard white grown for its flavor at the table, ready in roughly 88 to 92 days.
Bodacious
A sugary-enhanced yellow with tender, sweet kernels that arrive around 75 days.
Ambrosia
A sugary-enhanced bicolor of yellow and white kernels, also about 75 days, and a longtime favorite in home gardens.
How Sweet It Is
A supersweet white that keeps its sugar longest after the harvest, asking only for warm soil and a little distance from other corn types.
Companions
Corn grows best with the partners that share its bed in the old Three Sisters planting, and worst beside crops that feed the same pests it does.
Plant near
Pole beans: Traditional Three Sisters partner; beans fix nitrogen that benefits this heavy-feeding crop and use cornstalks as a living trellis
Squash: Traditional Three Sisters partner; broad squash leaves shade the soil, conserving moisture and suppressing weeds around corn
Keep apart
Tomatoes: Corn earworm and tomato fruitworm are the same insect (Helicoverpa zea), so adjacent plantings build shared pest pressure
How to propagate
Corn enters the garden a single way, from seed sown right where it will stand, since it would rather its roots were left undisturbed.
SeedEasy
Direct sow after the last frost when soil is at least 60°F (16°C); make succession sowings every 2-3 weeks for a continuous harvest · Seeds germinate in about 4-10 days in warm soil
Corn comes into the garden one unhurried way, from seed dropped straight into the bed where it will stand all summer, since it would rather not be lifted and moved. Set the seeds 1 to 1.5 inches deep and 8 to 12 inches apart in a block of three or four rows so the wind can carry pollen across them, and the first green spears show in about 4 to 10 days once the soil has warmed. A fresh patch every 2 to 3 weeks keeps ears arriving through the season, and a supersweet variety wants room away from other types, since cross-pollination turns its kernels starchy.
Myths
Clearing the side shoots from the foot of the stalk yields more corn.
The shoots that rise at the base, known as tillers or suckers, do no harm when left to stand. Stripping them away adds nothing to the yield, and the open wounds can stress the plant or invite disease, so leave the tillers alone.
A solitary long row will fill its ears nicely if the plants look well.
Corn leans on the wind for pollination, and each silk waits on its own grain of pollen to set a kernel. A lone row gathers far too little, and the ears come in gappy, so plant in blocks of at least three or four short rows for a fuller harvest.