Broadfork™

Crop guide

Sweet corn

Sweet corn goes in after the frost, once the soil has warmed, in a block of short rows. Pick it at the milk stage and get it cold.

Grown in Ohio, zone 6a. Your frost dates move the calendar; the signals don't. Broadfork goes by where your garden is, not its zone: frost dates for your ZIP code in the US, or the ones you type in anywhere else.

Nine minutes to read. Each section stands on its own.

A tall sweet corn plant with long arching leaves and a tassel at the top. Two ears grow from the stalk in green husks with red-brown silks, one husk opened to show yellow kernels, and fine roots spread through the soil below.
What you plant
Seed, sown where it will grow. Buy fresh seed each year: it keeps about 2 years.
When
After the frost, once the soil is 50 to 60 °F for standard sweet corn, 60 to 65 for the supersweets.
How deep
About 1 inch in heavy soil, up to 2 in sand. Supersweets no deeper than 3/4 to 1 inch.
How far apart
8 to 12 inches apart in rows 30 to 36 inches apart, in a block of at least four short rows. In a bed with no paths between rows, the plants go the same distance apart every way, 15 to 18 inches, and the app spaces it 15 inches apart.
Sun and soil
Full sun, 8 to 10 hours; some data goes as low as 6. Fertile soil that drains, and never fresh manure.
Frost
Tender: frost injures it at any stage, though one source says a young plant takes a light frost. It grows best at 60 to 80 °F.
Family
Poaceae, the grasses, with popcorn, wheat, oats and rye.
Harvest
At the milk stage, about 20 days after the first silks: silks brown and dry, the husk green and tight, milky juice in a kernel.
Soil pH
6.0 to 7.0; the data goes as low as 5.8.
winterspringsummerfall last frost first sowingsoil at 50 to 60 °F sow again every 2 weeks last sowingabout July 1 first picking20 days after the silks first fall frostends it
  1. springFirst sowing once the soil reaches 50 to 60 °F; supersweets wait for 60 to 65.
  2. summerSow again every 2 weeks, until about July 1.
  3. summerPick each sowing about 20 days after its first silks.
  4. fallThe first frost ends it.
Sweet corn's year. It runs from the last frost to the first, so your frost dates set it, not the month. The green bar is the picking.

Planting#

Wait for warm soil, and go by the type on the packet: standard (su) at 50 to 60 °F, sugary enhanced (se) a week later, supersweet (sh2) at 60 to 65. Cold, wet soil rots the seed, and untreated seed wants 65 °F.

Sow 1 inch deep in heavy soil, up to 2 in sand. Supersweet seed is small and brittle and needs more water to sprout: sow it no deeper than 3/4 to 1 inch and keep the bed moist.

Plant a block, not a row. Wind carries the pollen from the tassels to the silks, one silk to a kernel, and a single row leaves ears with gaps. Sow at least four short rows, 30 to 36 inches apart, the seed 8 to 12 inches apart.

From the beds in OhioWhat sometimes makes sweet corn difficult to grow at home is pollination. Plant bigger blocks, all sown at the same time, so more pollen reaches more silks: every kernel has to be pollinated to fill out a full ear with straight rows.

Pole beans grown up the corn, with squash below, make the Three Sisters: a tradition, and the evidence for it is disputed.

For corn all summer, sow the same variety every 2 weeks; the data runs from 7 days to 3 weeks. Or sow early, midseason and late varieties together. Stop about July 1, quickest varieties last: corn ripening in the cool September nights is almost always the best.

Short season Where the season is short, grow varieties under 80 days. Clear plastic over the row warms the soil: leave the plants under it 2 to 4 weeks, and slit it before it overheats. A low tunnel gives about a two-week start.

Mild winter Where winters are mild, sowing starts from February into April, and the warmest places sow again from mid-July for a fall crop.

1 to 2 insoil surface8 to 12 in 30 to 36 intasselsshed pollensilkscatch itfour rows
In the ground. Seed 1 to 2 inches deep and 8 to 12 inches apart, in rows 30 to 36 inches apart, four or more side by side.

The season in between#

Give it about 1 inch of water a week; the data runs to 2. Don't let it go dry from about 2 weeks before the silks show until the ears fill.

Corn is a heavy feeder. Work in about 2 to 3 pounds of 10-10-10 per 100 square feet before planting, then side-dress with nitrogen. The data splits on when, from 3 or 4 inches tall to 2 feet, and some data feeds again at the tassels.

In Broadfork Log 8 to 10 inches tall on a corn planting and the app asks for the first feed; log Tassels showing and it dates the second.

Leave the suckers. Pulling them doesn't raise the yield and can cut it.

Weed shallow, since the roots run near the surface, and mulch with straw once the plants are 4 to 5 inches tall.

Mild winter Where summers run hot, air above 95 °F and drying winds at pollination leave poorly filled ears. Water every 5 to 7 days if the rain doesn't.

Harvest#

Pick at the milk stage: silks brown and dry, the husk green and tight, the ear full to a blunt tip. Press a kernel with a thumbnail: milky juice is ready, clear is early, doughy is late. Supersweets read differently, since a ripe kernel can still run clear: go by the silks and the days.

Count about 20 days from the first silks; the data runs from 17 to 24, and 15 or less in heat. Two sources count 3 weeks from the tassel instead. The stage lasts under a week, and above 85 °F only a day or two.

In Broadfork Log First silks on a corn planting and its picking window lines up 18 to 23 days after.

Pick in the cool of the morning: hold the ear at its base, push it down, twist and pull.

Get it cold fast. Standard corn left warm can lose half its sugar in 12 hours; supersweet and sugary enhanced corn lose it more slowly. If it's hot, plunge the ears in ice water first.

Expect one good ear to a stalk, and plan on 10 to 15 feet of row a person to eat fresh.

Storing#

Keep the ears in their husks in the refrigerator, near 32 °F, and use them within two days. Standard corn holds 1 to 2 days and supersweets about a week; the data runs to 2 to 3 weeks for the newest kinds.

From the beds in OhioOn harvest day, put a pot of water on to boil before you go out to pick. Back inside, shuck the ears you're keeping and blanch them right away. The sugar starts turning to starch as soon as an ear is picked, so the sooner it's blanched and cooled, the less starchy it tastes.

To freeze kernels, blanch the ears 4 minutes, cool them and cut at 2/3 of the kernel's depth; some data blanches 3 minutes and cuts at 3/4. On the cob, blanch 7 minutes for a small ear, 9 for medium and 11 for large.

Can corn only in a pressure canner, never a boiling-water bath.

Which sweet corn#

The code on the packet is the type. Standard, su, is creamy with the old corn flavor, but turns starchy fastest: eat it the day it's picked. Sugary enhanced, se, is sweeter and still tender. Supersweet, sh2, has two to three times the sugar of su and keeps up to a week, with a crisper, less creamy kernel.

Keep the types from crossing: popcorn or field corn pollen makes sweet corn starchy, and any other type's pollen spoils a supersweet. In a garden, time works better than distance: sow so the two tassel at least 14 days apart; the data runs from 12 days to a month. By distance it runs from 50 feet to 400 yards. Most data lets se grow beside su; some keeps them apart. Seed kept for sowing needs far more room: save your own seed.

In Broadfork Place a second named kind of corn in a bed, or list two on the Grow List, and the app says to keep their tasseling 14 or more days apart.

In the app's catalog, among others: Silver Queen, Bodacious, Incredible, How Sweet It Is, Honey Select and Golden Bantam.

Short season Where the season is short, grow varieties under 80 days. Su types sprout best in cool soil, and Earlivee is named as dependable in cool weather.

Mild winter Where summers are hot, grow heat-tolerant varieties; for the warmest places the advice is se or sh2, one type only.

What goes wrong#

Mild winter Where winters are mild, earworm lives through the winter and has two to three generations or more, so the late sowings take the most damage.

Where it goes next year#

Corn and popcorn rest as their own group: keep them out of a bed for 3 to 4 years after they grow there. A grass cover crop, like rye or oats, isn't counted as a corn year.

Smut spores and rootworm eggs stay in the soil, and rootworm grubs live only on corn roots. The borer winters in the stalks instead, Stewart's wilt rides the flea beetle and rust blows in.

The data splits on spent stalks: shred and compost them, or take them out, since the borer winters inside. Then cover the soil.

Corn takes a lot of nitrogen, so the data puts a legume year after it: beans, or a clover or vetch cover. End a rye cover crop 10 to 14 days before sowing corn.

Every number on this page comes from a published extension source.

Sources for this guide: Clemson Cooperative Extension, Iowa State University Extension and Outreach, Ohio State University Extension, University of Illinois Extension, University of Maryland Extension, NC State Extension, Penn State Extension, Texas A&M AgriLife Extension, University of Minnesota Extension, New Mexico State, Purdue Extension, University of Missouri Extension, University of Wisconsin-Madison Division of Extension, Utah State University Extension, Alabama Cooperative Extension System, Colorado State University Extension, Cornell Cooperative Extension, Kansas State, National Center for Home Food Preservation, NDSU Extension, SDSU Extension, UMass Extension, University of Alaska Fairbanks, University of California, University of Delaware Cooperative Extension, University of Florida, University of Georgia Extension, University of Nebraska–Lincoln Extension, University of New Hampshire Extension, Virginia Cooperative Extension, WVU Extension.

The documents behind this guide (59)

Updated 11/11/2026 · Checked against our sources 11/12/2026

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