Vegetable · Poaceae
Sweet Corn
Zea mays
Put it in a block, not a row, feed it well, and sweet corn pays you back with full, milky ears by late summer.
Full sun
Every 3–7 days
50–95°F · 10–35°C
60–100 days
Overview
Sweet corn's a tall grass you grow for those sugary ears that show up in high summer. It goes way back to the Americas, where people bred it from wild grasses thousands of years ago, and these days it grows as a warm season annual in gardens just about everywhere. Give it sun, warmth, and rich ground, and even a few square feet can hand you a real summer crop.
Here's the one thing corn asks for that most vegetables don't: a little company. It pollinates on the wind, with pollen falling from the tassels up top onto the silks below, so a single plant or one lonely row sets badly. Plant it in a block of several short rows instead, and the wind does the heavy lifting, filling every ear from butt to tip.
Corn's a hungry plant, no two ways about it. It wants steady water and a real heavy hand with nitrogen, and it's got zero patience for cold soil or crowding. Get the timing and the feeding right and it grows fast, but cut corners and you'll trade full cobs for gappy, half-filled ears.
Care
The short version: give it full sun, rich soil, and plenty of water, and plant it in a block instead of a single row so the wind can pollinate it. Feed it well, since corn's a heavy nitrogen feeder, and keep it moist once the silks show up.
Light
Corn wants full sun, and honestly the more the better, with no shade if you can help it. It's tall and quick-growing, so it shades itself plenty already, which means you'll want to give it the most open, sunny spot you've got.
Water
Keep the soil evenly moist, somewhere around an inch of water a week. The moisture matters most from tasseling and silking through ear fill, because a dry spell right then is what leaves you with poorly filled ears.
Soil
Go for fertile, well drained loam with lots of organic matter worked in. A pH of 6.0 to 6.8 suits it best, and that rich ground is exactly what feeds the big appetite corn shows up with.
Temperature
Corn does fine across a wide range, from about 50°F to 95°F (10°C to 35°C), but it needs warm soil to get going and a long warm stretch to ripen. Sow it into cold ground and the seed just rots before it can sprout.
Humidity
Regular outdoor humidity is all it needs, so there's no number to chase here. What matters way more is the wind, since that's what carries the pollen from tassel to silk and fills out the ears.
Feeding
Corn's a heavy nitrogen feeder, plain and simple. Work a balanced fertilizer in at planting, then side-dress with nitrogen once the plants hit about a foot tall, and again when they tassel.
Pruning
There's nothing to prune here, which is nice. Leave the tillers that come up at the base of the stalks, since taking them off won't get you more corn and can actually cost you some. The only thing to cut out is smut galls or stalks that are clearly diseased.
Size & spacing
Stalks get 5 to 8 feet (150 to 250 cm) tall but don't take up much width, so you can set plants pretty close, about 8 to 12 inches (20 to 30 cm) apart. Pack them into a block of several short rows rather than one long line.
When to plant
Corn's all about warmth, and it can't handle frost at all. So wait until the cold's gone and the soil's warmed up to at least 60°F (16°C), then sow the seed right in the ground. Pop in a fresh patch every couple of weeks and you'll be picking ears from midsummer into early fall.
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 corn trouble shows up on the ears or the stalks, and a lot of it traces back to how the plant got set out, not to some pest. Catch the early signs and you can usually save the crop, or at least the cobs that are already on the plant. Find what matches below, then act while it'll still do some good.
Chewed-up kernels and a caterpillar near the top of the ear
Found a caterpillar chewing the kernels up top? That's the corn earworm, which slips down the silk channel and feeds right at the tip. Here's the good news, though: the damage almost never gets past the first few inches, so you can just cut the tip off and the rest of the cob's still great. To keep the next ones out, put a few drops of mineral oil on the silks a few days after they show up, or give the fresh silks a quick Bt spray.
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
Ears that turned out gappy, with shriveled or missing kernels
Those gaps and shriveled spots? They almost always come down to poor pollination, usually because the corn went in as one lonely row the wind couldn't carry pollen across. A dry stretch during silking doesn't help either. Next time, plant a block of three or four short rows, keep the soil moist once the tassels show, and if a small patch comes up thin you can even shake the tassels over the silks by hand.
Fix:
- Water deeply during silking and ear fill
- Hand-pollinate small plantings by shaking tassels over fresh silks
Puffy gray galls that break open into black powder
Those puffy lumps are common smut, a fungus that sneaks in through little wounds and really takes off in hot, dry weather, especially if you've gone heavy on the nitrogen. They start out firm and silvery, then turn dark and split open to spill powdery black spores everywhere. Cut them out and toss them in the trash before they burst, and whatever you do, don't put them in the compost.
Fix:
- Remove and destroy galls before they rupture; do not compost them
Stalks that lean over or snap when the wind picks up
Before you blame the storm, take a look at the base, because corn falls over for two pretty different reasons. Sometimes it's just shallow roots in loose soil that couldn't hold on, but small entry holes ringed with sawdust-like frass mean a corn borer has been tunneling the stalk from the inside. Stand the plants back up and mound some soil around the base, and at the end of the season shred and till in the old stalks so the borers can't overwinter in there.
Fix:
- Gently stand plants back up and hill soil around the base after storms
- Destroy crop residue after harvest to remove overwintering borers
Rusty orange dots and long tan streaks marking the leaves
If the orange spots smudge off on your fingers, that's common rust, but long cigar-shaped gray-tan streaks usually mean northern corn leaf blight showing up in warm, humid weather. Late in the season neither one really hurts the crop, so you can mostly just let them go. Pull off the worst of the lower leaves if you want, and pick resistant hybrids next year so you stay a step ahead.
Fix:
- Remove heavily infected lower leaves
- Severe cases on young plants may warrant a labeled fungicide; late-season infection rarely needs treatment
Toxicity
Good news up front: sweet corn's safe. No part of the plant is poisonous to people, pets, or livestock, which is why it ends up on dinner plates and in animal feed alike. The one thing to keep an eye on is the bare cob, since a dog can swallow one and choke or block its gut, so keep finished cobs out of reach.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
No poison here, so there's nothing to stress about. If a cat chews a leaf or a stray kernel, the plant itself won't do it any harm.
Dogs None
A dog won't get poisoned by the plant, but the cob's a whole different kind of problem. Swallow one, or even a chunk, and it can get stuck and block the gut, so keep whole cobs somewhere the dog can't reach.
Horses Safe
Grain corn's a pretty common feed, and there's nothing in the plant that would bother a horse.
Rabbits Safe
It's fine for a rabbit to nibble, though they'll do best on leafy greens with just a bit of corn now and then.
Livestock Safe
Corn's fed cattle, sheep, and goats forever, and there's no toxin in it to worry about.
Birds Safe
Hens and wild birds love the kernels, and nothing in the plant will hurt them.
People Safe
Sweet corn's a kitchen regular, eaten fresh off the cob or cooked, and there's no part you've got to skip.
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 comes in standard, sugary-enhanced, and supersweet types, and each one holds its sugar a little differently after you pick it. Here are a few worth knowing by name.
Silver Queen
A classic standard white that folks grow for the flavor, and it's ready in roughly 88 to 92 days.
Bodacious
A sugary-enhanced yellow with tender, sweet kernels you can pick around 75 days.
Ambrosia
A sugary-enhanced bicolor of yellow and white kernels, also about 75 days, and a real home-garden favorite.
How Sweet It Is
A supersweet white that hangs onto its sugar longest after picking, as long as you give it warm soil and keep it away 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
There's really only one way to grow corn, and that's from seed sown right where it'll stand, because it hates having its roots messed with.
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's about as simple as it gets, because you just sow it straight where it'll grow and skip transplanting, which it hates anyway. Tuck 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 pollinate them, and they'll pop up in about 4 to 10 days once the soil's warm. Want corn coming all season? Sow a fresh patch every 2 to 3 weeks, and just remember to keep any supersweet variety away from other types, since cross-pollination turns the kernels starchy.
Myths
Tearing off those little shoots at the bottom of the stalk gets you a bigger crop.
Those little shoots at the base, the ones called tillers or suckers, won't cause any trouble if you just leave them be. Pulling them off doesn't get you more corn, and the open wounds can stress the plant or let disease sneak in, so leave the tillers alone.
One long solo row does just fine when the plants seem happy.
Here's the thing: corn pollinates on the wind, and every single silk needs a grain of pollen to make a kernel. One row just doesn't catch enough, so you end up with gappy ears, which is why you'll want to plant in blocks of at least three or four short rows instead.