When to Plant Sweet corn & Best Companion Plants

Companion plants for sweet corn

What to grow next to sweet corn, what to keep away, and what is only tradition. Every pairing says how strong the evidence is.

Grow together 9

Helps, or shares the bed well.

Bush bean Mixed Part of the Three Sisters. Pole beans climb the corn. Research on yield benefits is mixed: one study found more food per acre overall, others found lower bean yields.

Source: Food Yields and Nutrient Analyses of the Three Sisters, Jane Mt. Pleasant, Ethnobiology Letters 7(1), 2016; Gardening with Companion Plants (EM128E), Linda Chalker-Scott, Washington State University Extension, 2023. Bush bean guide
Pole bean Mixed Part of the Three Sisters. Pole beans climb the corn. Research on yield benefits is mixed: one study found more food per acre overall, others found lower bean yields.

Source: Food Yields and Nutrient Analyses of the Three Sisters, Jane Mt. Pleasant, Ethnobiology Letters 7(1), 2016; Gardening with Companion Plants (EM128E), Linda Chalker-Scott, Washington State University Extension, 2023. Pole bean guide
Winter squash Mixed The third sister: squash leaves shade the soil and smother weeds under the corn. The combined planting yields well per acre, though each crop on its own yields less.

Source: Food Yields and Nutrient Analyses of the Three Sisters, Jane Mt. Pleasant, Ethnobiology Letters 7(1), 2016; Gardening with Companion Plants (EM128E), Linda Chalker-Scott, Washington State University Extension, 2023. Winter squash guide
Pumpkin Mixed The third sister: squash leaves shade the soil and smother weeds under the corn. The combined planting yields well per acre, though each crop on its own yields less.

Source: Food Yields and Nutrient Analyses of the Three Sisters, Jane Mt. Pleasant, Ethnobiology Letters 7(1), 2016; Gardening with Companion Plants (EM128E), Linda Chalker-Scott, Washington State University Extension, 2023. Pumpkin guide
Cucumber Practical Cucumbers can climb corn stalks, and corn tolerates the vines at its base.

Cucumber guide
Cantaloupe Practical Vines run happily under corn and use the space between rows.

Cantaloupe guide
Pea Practical Peas leave nitrogen-rich roots behind; corn planted in the same spot afterward benefits.

Source: Gardening with Companion Plants (EM128E), Linda Chalker-Scott, Washington State University Extension, 2023. Pea guide
Lettuce Practical Tall crops give lettuce the afternoon shade that slows bolting in summer.

Lettuce guide
Red leaf lettuce Practical Tall crops give lettuce the afternoon shade that slows bolting in summer.

Red leaf lettuce guide

Keep apart 2

Shared pests, disease or competition.

Tomato Practical The corn earworm is the same insect as the tomato fruitworm. A corn patch next to tomatoes feeds both stages of the same pest.

Tomato guide
Cherry tomato Practical The corn earworm is the same insect as the tomato fruitworm. A corn patch next to tomatoes feeds both stages of the same pest.

Cherry tomato guide

Tradition only 1

On many charts, with little or no evidence.

Sunflower Tradition Said to help Both tall and hungry; they compete as much as they help.

Sunflower guide

Studied Field or lab research shows an effect, at least under some conditions.

Mixed Some studies find an effect, others don’t, or it only works in a narrow way.

Practical Explained by light, space, timing, support or a shared pest or disease.

Tradition Widely repeated, but with little or no evidence behind it.

See every pairing side by side in the companion planting chart, or try them in a bed with the garden planner.

When to plant sweet corn by city

Sow sweet corn outdoors 1–4 weeks after your last frost, once the soil is at least 60°F. Here is what that means for 2027 in cities across the US, using each city’s average frost dates and the date its normal daily temperature reaches 60°F, so cool-spring places like Seattle wait for real warmth (NOAA 1991–2020). Pick the city with the climate most like yours, or enter your ZIP code above.

City	Last frost	Sow outdoors
Seattle, WA (9a)	Mar 13	May 29 – Jun 19
Portland, OR (8b)	Feb 25	May 24 – Jun 14
Sacramento, CA (9b)	Jan 12	Apr 5–26
Phoenix, AZ (10a)	Jan 5	Feb 15 – Mar 8
Salt Lake City, UT (7b)	Mar 31	May 8–29
Denver, CO (6a)	Apr 30	May 17 – Jun 7
Dallas, TX (8b)	Mar 2	Mar 17 – Apr 7
Minneapolis, MN (5a)	Apr 23	May 19 – Jun 9
Kansas City, MO (6b)	Apr 4	Apr 25 – May 16
Chicago, IL (6b)	Apr 10	May 22 – Jun 12
Columbus, OH (6b)	Apr 20	May 7–28
Nashville, TN (7b)	Apr 1	Apr 16 – May 7
Atlanta, GA (8a)	Mar 24	Apr 8–29
Raleigh, NC (8a)	Mar 28	Apr 13 – May 4
Philadelphia, PA (7b)	Mar 30	Apr 27 – May 18
Boston, MA (7a)	Apr 4	May 20 – Jun 10

In frost-free parts of Florida, southern California and the Gulf Coast, timing is about heat instead: plant sweet corn in late winter or early spring and again in late summer.

Don’t go by the calendar alone. Sweet corn planted into cold soil sit still for weeks; wait until the soil 4 inches down is at least 60°F and nights stay above 50°F.

Sweet corn spacing

In a square-foot bed, plant 1 per square foot. In traditional rows, space plants about 12 inches apart with 30 inches between rows.

Wind-pollinated: plant a block at least 4 rows deep, not one long row.

One square foot planted with sweet corn, as drawn in the planner.

How to grow sweet corn

Freshly picked sweet corn is one of the great pleasures of a home garden, but it needs space, sun and plenty of nitrogen. Corn is wind-pollinated, so it should be planted in a block of short rows rather than one long row, or the ears fill out poorly.

Sun and soil

Full sun and fertile, well-drained soil with a pH of about 6.0–6.8. Corn is a heavy feeder. Keep soil moist, about 1–1½ inches of water a week, especially from tasseling through ear fill.

Planting

Sow 1 inch deep, 1–4 weeks after the last frost, once soil is at least 60°F. Supersweet (sh2) varieties need warmer soil, closer to 65°F.
Space seeds 12 inches apart in rows 30 inches apart.
Plant a block at least 4 rows deep for good pollination.
For a longer harvest, plant early, mid- and late-season varieties together, or sow a new block every 10–14 days.

Care

Side-dress with nitrogen when plants are knee-high (8–10 leaves) and again when tassels appear.
Water deeply during tasseling and silking; drought then means poorly filled ears.
Keep sugary-enhanced, supersweet and standard types from tasseling at the same time, or cross-pollination makes kernels starchy. Stagger planting dates or maturity.
Leave the side shoots (suckers) alone; removing them does not help.

Harvest

Ears are ready about 3 weeks after silks appear, when silks are brown and dry, the ear feels full, and a kernel near the tip squirts milky juice when pressed with a thumbnail. Pick by pulling the ear down and twisting. Cook or refrigerate right away, because sugars turn to starch after picking.

Common problems

Corn earworm: Caterpillars feed on ear tips. Apply a few drops of mineral oil to the silk tip once silks begin to brown, or simply cut off the damaged tip at harvest.
Raccoons: They raid corn the night before you planned to pick. An electric fence with two wires about 4 and 8 inches above ground, turned on before ears ripen, is the most effective protection.
Corn smut: Swollen gray galls on ears and stalks. Remove galls before they break open and release spores; rotate plantings.
Poorly filled ears: Usually poor pollination from planting in a single row, or drought at silking. Plant in blocks and water during tasseling.

Varieties to try

'Bodacious' — yellow, sugary-enhanced, widely adapted
'Ambrosia' — bicolor, sugary-enhanced, tender
'Silver Queen' — late white, standard sweet corn
'Early Sunglow' — early yellow for short seasons

Crop rotation

Sweet corn belong to the grass family (Poaceae). Corn is a very heavy nitrogen feeder; follow it with legumes.

Frequently asked questions

When should I plant sweet corn?

Sow sweet corn outdoors 1–4 weeks after your last frost, once the soil is at least 60°F. Type your ZIP code above for exact dates, or see the city table.

What grows well with sweet corn?

Good neighbors for sweet corn include bush bean, pole bean, winter squash, pumpkin, cucumber and cantaloupe. Each one is listed above with the reason and how strong the evidence is.

What should not be planted with sweet corn?

Keep sweet corn apart from tomato and cherry tomato. The corn earworm is the same insect as the tomato fruitworm. A corn patch next to tomatoes feeds both stages of the same pest.

How far apart should I plant sweet corn?

In rows, space sweet corn about 12 inches apart with rows 30 inches apart. In a square-foot bed, plant 1 per square foot.

How long do sweet corn take to grow?

About 65–90 days from sowing to first harvest, depending on the variety and the weather.

Can sweet corn handle frost?

No. Sweet corn are killed by frost and sulk in cold soil, so wait until after your last frost and until the soil reaches about 60°F.

Sources

Frost dates: NOAA National Centers for Environmental Information, U.S. Climate Normals 1991–2020.
Hardiness zones: 2023 USDA Plant Hardiness Zone Map, USDA-ARS and PRISM Climate Group, Oregon State University.
Planting windows and spacing: Vegetable Planting Guide (GardenNotes #720), Colorado State University Extension, and other land-grant extension guides.
Food Yields and Nutrient Analyses of the Three Sisters, Jane Mt. Pleasant, Ethnobiology Letters 7(1), 2016
Gardening with Companion Plants (EM128E), Linda Chalker-Scott, Washington State University Extension, 2023
Sweet Corn in the Garden — Utah State University Extension

More free garden tools

Plan your beds

Garden planner
Draw your beds square by square and check every neighbor.
Square foot gardening chart
How many of each plant fit in one square foot.
Raised bed soil calculator
Cubic feet, cubic yards and bags for any bed.
Three Sisters garden
Corn, beans and squash: layout, timing and what the research says.

When to plant

Planting calendar
Sowing and planting dates for your ZIP code.
Frost dates by ZIP code
Last spring and first fall frost, with the odds.
Growing zone by ZIP code
Your USDA hardiness zone and what it does and doesn’t tell you.
Seed starting calculator
When to start each seed indoors.

What grows together

Companion planting chart
Good and bad neighbors, graded by evidence.
Plant guides
When to plant and what to plant with 55 vegetables, herbs and flowers.