Oregon · Washington · Idaho
When to plant sweet corn
Plant in the garden: Portland and Seattle May 10 – Jun 14; Spokane May 15 – Jun 19; Boise May 1 – Jun 5; Bend Jun 16 – Jul 21.
Your dates in
Sweet corn is corn picked young, while the kernels are still milky, and eaten fresh off the cob. Seed packets label varieties by sweetness, from standard (su) to sugary enhanced (se) and supersweet (sh2), and supersweets need to be kept apart from other types to stay sweet. Ears are at their sweetest right after picking, because the sugar starts turning to starch soon after harvest.
Puts sweet corn on your free plan, with dates for your town and a spot in your beds.
- Difficulty
- Moderate
- Sun
- Full sun
- Spacing
- 10 inches apart in a block of short rows
- Planting depth
- 1 inch deep
- Frost
- Killed by frost
- First harvest
- About 80 days after planting
Plant in blocks of at least four short rows, not one long row, for good pollination.
Sweet corn planting dates
| Towns | Plant in the garden |
|---|---|
| Portland, OR, Seattle and Tacoma, WA | May 10 – Jun 14 |
| Spokane, WA, Astoria, OR | May 15 – Jun 19 |
| Boise and Meridian, ID | May 1 – Jun 5 |
| Bend and Redmond, OR | Jun 16 – Jul 21 |
Dates for six main cities. For any of the other 80 towns, type it in the box at the top of the page or browse all towns.
| Gresham, OR, Hillsboro and Beaverton, OR, Oregon City and West Linn, OR, Portland, OR, St. Helens and Scappoose, OR, Wilsonville and Canby, OR | May 10 – Jun 14 |
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| Corvallis and Albany, OR, Cottage Grove, OR, Eugene, OR, McMinnville and Newberg, OR, Salem, OR | May 10 – Jun 14 |
|---|
| Ashland and Talent, OR | May 13 – Jun 17 |
|---|---|
| Grants Pass, OR, Medford, OR, Roseburg, OR | May 10 – Jun 14 |
| Astoria, OR, Brookings and Gold Beach, OR, Coos Bay and North Bend, OR, Newport and Lincoln City, OR, Tillamook, OR | May 15 – Jun 19 |
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| Bend and Redmond, OR, Klamath Falls, OR | Jun 16 – Jul 21 |
|---|---|
| Burns, OR | Jun 18 – Jul 23 |
| Lakeview, OR | Jun 11 – Jul 16 |
| Madras, OR | May 26 – Jun 30 |
| Prineville, OR | Jun 8 – Jul 13 |
| Baker City, OR | Jun 1 – Jul 6 |
|---|---|
| Enterprise and Joseph, OR | May 31 – Jul 5 |
| Hermiston, OR, Pendleton, OR | May 3 – Jun 7 |
| Hood River, OR | Apr 27 – Jun 1 |
| John Day, OR | Jun 4 – Jul 9 |
| La Grande, OR | May 15 – Jun 19 |
| Ontario, OR | Apr 28 – Jun 2 |
| The Dalles, OR | Apr 25 – May 30 |
| Bremerton and Port Orchard, WA, Everett, WA, Kent, Renton and Auburn, WA, Olympia, WA, Seattle and Tacoma, WA, Shelton, WA | May 10 – Jun 14 |
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| Anacortes, WA, Bellingham, WA, Friday Harbor and the San Juans, WA, Mount Vernon and Burlington, WA, Oak Harbor and Whidbey Island, WA | May 10 – Jun 14 |
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| Aberdeen and Hoquiam, WA, Forks, WA, Long Beach and Ilwaco, WA | May 15 – Jun 19 |
|---|---|
| Port Angeles, WA, Port Townsend, WA, Sequim, WA | May 10 – Jun 14 |
| Centralia and Chehalis, WA, Longview and Kelso, WA, Vancouver, WA | May 10 – Jun 14 |
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| Chelan, WA, Wenatchee, WA | Apr 25 – May 30 |
|---|---|
| Leavenworth, WA | May 17 – Jun 21 |
| Omak and Okanogan, WA | May 15 – Jun 19 |
| Winthrop and Twisp, WA | May 22 – Jun 26 |
| Ellensburg, WA, Yakima, WA | May 15 – Jun 19 |
|---|---|
| Ephrata and Quincy, WA | Apr 29 – Jun 3 |
| Goldendale, WA | May 26 – Jun 30 |
| Moses Lake, WA, Tri-Cities (Pasco, Kennewick, Richland), WA | May 4 – Jun 8 |
| Sunnyside, Grandview and Prosser, WA | May 8 – Jun 12 |
| Walla Walla, WA | Apr 25 – May 30 |
| Colville, WA, Pullman, WA, Spokane, WA | May 15 – Jun 19 |
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| Bonners Ferry, ID, Coeur d'Alene and Post Falls, ID, Sandpoint, ID | May 15 – Jun 19 |
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| Lewiston, ID | Apr 25 – May 30 |
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| Moscow, ID | May 15 – Jun 19 |
| Boise and Meridian, ID | May 1 – Jun 5 |
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| Emmett, ID | May 7 – Jun 11 |
| McCall, ID | Jun 29 – Aug 3 |
| Nampa and Caldwell, ID | May 6 – Jun 10 |
| Burley and Rupert, ID, Pocatello, ID | May 15 – Jun 19 |
|---|---|
| Idaho Falls, ID, Twin Falls, ID | May 16 – Jun 20 |
| Rexburg, ID | May 19 – Jun 23 |
| Salmon, ID | May 25 – Jun 29 |
Sweet corn year at a glance
| Task | J | F | M | A | M | J | J | A | S | O | N | D |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Plant | May | Jun | ||||||||||
| Harvest | Aug | Sep |
Around Portland. Colder towns, especially east of the Cascades, run a few weeks later; the table above has your town's planting dates.
How to grow sweet corn
- Prepare the bed: loosen the soil and mix in an inch or two of compost.
- Plant seeds on your city's dates, 1 inch deep, 10 inches apart in a block of short rows.
- Keep the soil evenly moist until sprouts appear, which can take one to three weeks in cool soil.
- Harvest: Ready about three weeks after the silks appear, when the silks are brown and the kernels squirt milky juice.
Growing sweet corn in your part of the Northwest
The same plant behaves differently on the wet west side, the foggy coast and the dry, colder east side.
West-side valleys
Willamette Valley, Puget Sound, southern Oregon
Sweet corn needs warm soil to sprout, so wait until late May. Pick early to mid-season varieties; very late ones may not ripen in a cool summer.
Coast
Oregon and Washington coast
Cool summers make sweet corn hard to ripen. Choose the earliest varieties and plant in your warmest spot.
East of the Cascades
Columbia Basin, Yakima, Boise, Spokane, north Idaho
Hot summers suit corn well, and it is one of the classic east-side garden crops. Water deeply when tassels and silks appear, since drought then gives poorly filled ears.
High desert and mountain towns
Central Oregon, high eastern Oregon valleys, McCall, Salmon
Frost risk and cool nights shorten the season, so plant the earliest varieties after the last frost. Black plastic warms the soil and speeds things up.
More sweet corn varieties
More widely sold picks that do well somewhere in the Northwest. The tag says which part of the Northwest suits each one best.
Early Sunglow
Short plants with small ears of sweet yellow corn. It tolerates cool weather and is one of the most reliable sweet corns where summers are short or cool.
Short seasons
Bodacious
Large ears of tender, very sweet yellow kernels that hold their sweetness a few days after picking. A widely grown main-season corn.
Both sides
Golden Bantam
An open-pollinated heirloom with rich, old-fashioned corn flavor. Ears are smaller and the sugar fades faster after picking, so cook it right away.
Both sides
Ambrosia
Large ears of tender yellow and white kernels with excellent sweetness. A popular main-season bicolor that does well in warm summer spots.
Both sides
Silver Queen
Long ears of sweet, creamy white kernels. It needs a long, hot season, so it is best suited to warm gardens east of the Cascades.
East side
How much to grow
How many to plant
Plant at least four rows side by side, so wind pollinates the ears. For a family of four, a block of about 50 to 75 plants.
What to expect
One or two good ears per plant.
Storing the harvest
Sweetness fades within hours of picking, so cook right away or blanch and freeze. Supersweet types hold a few days in the fridge.
What to plant after sweet corn
Around Portland, the sweet corn harvest wraps up around September. These crops can still go into the same bed, and they come from a different plant family, which helps with rotation.
- Mâche Aug 13 – Sep 17
- Spinach Aug 20 – Sep 10
- Mustard greens Aug 20 – Sep 10
- Cilantro Aug 27 – Sep 10
- Arugula Aug 27 – Sep 17
- Radishes Sep 3–17
- Garlic Oct 1 – Nov 15
- Fava beans Oct 1–31
Mâche 
Spinach 
Mustard greens 
Cilantro 
Arugula 
Radishes 
Garlic 
Fava beans Portland dates. Pick your town at the top of the page for yours.
Key numbers
- 60°F or warmerSoil to sprout
- 5.8–7.0Soil pH
- 1+ inch a week at silkingWater
- Cold soil, crowsBiggest risk
Top care tip: Plant in a block of short rows rather than one long row so the wind pollinates every ear.
Growing notes
What makes the difference in Northwest gardens, in plain language.
Soil, warmth and feeding
Corn is a warm-season grass that sprouts poorly in soil below about 60°F, and seed often rots in cold, wet ground. West of the Cascades that usually means waiting until mid to late May, while hot eastern valleys can plant a bit earlier. Supersweet types are even fussier about cold soil. Corn is a heavy nitrogen feeder: work in compost and fertilizer before planting, then side-dress when plants are about knee high. A pH of roughly 5.8 to 7.0 is fine.
Pollination and why ears are half empty
Each kernel forms only if a grain of pollen lands on its own silk strand. Pollen falls from the tassels on top and drifts on the wind, which is why corn is planted in a block of short rows instead of one long row. Gappy ears usually mean poor pollination from too few plants, hot dry weather at silking, or drought. Water deeply when tassels and silks appear. Also keep sweet corn types apart: if a supersweet crosses with a regular sweet corn, the kernels can turn starchy.
Harvest, storage, and east vs west
Sweet corn's sugar starts turning to starch the moment you pick it, so harvest right before cooking or chill ears quickly in the fridge. Check ears about three weeks after silking: brown silks, a full rounded tip and milky juice in the kernels mean ready. West of the Cascades, choose quicker varieties like Early Sunglow and Golden Bantam that finish before cool fall weather. East of the Cascades, longer-season types like Bodacious ripen easily, but watch for raccoons as ears near ripeness.
Good neighbors and crop rotation
Good neighbors
- Pole or runner beans. They climb the stalks once the corn is a foot tall.
- Winter squash. Shades the ground below and keeps weeds down.
Grass family: Corn is a heavy nitrogen feeder with no close relatives in the vegetable garden. Follow it with peas or beans, or a cover crop, rather than another hungry crop.
Pests and problems
What most often goes wrong with sweet corn in Northwest gardens, how to spot it and what to do.
Crows and jays
Signs: Seedlings pulled up just after they sprout.
What to do: Row cover or netting until plants are about 4 inches tall.
Corn earworm
Signs: A caterpillar eating the tip of the ear.
What to do: Cut off the damaged tip; the rest is fine. A few drops of mineral oil on the silks after pollination deters them.
Poorly filled ears
Signs: Ears with gaps and missing kernels.
What to do: Plant in blocks, not one long row, so pollen reaches every silk.
Common questions about growing sweet corn
When should I plant sweet corn in Oregon, Washington and Idaho?
Plant in the garden: May 10 – Jun 14 in Portland and Seattle, May 15 – Jun 19 in Spokane, May 1 – Jun 5 in Boise and Jun 16 – Jul 21 in Bend. Pick your town at the top of the page for your own dates.
Why are there missing kernels on my corn?
Those kernels weren't pollinated. Plant in blocks of at least four short rows so pollen falls onto neighboring silks, and water well when plants tassel. Heat and drought at silking also cause gaps.
When should I plant corn in western Oregon or Washington?
Wait until the soil is at least 60°F, which is usually mid to late May. Seed planted earlier in cold, wet soil often rots before it sprouts. Black plastic or a clear cover for a week can warm the bed faster.
Why isn't my sweet corn sweet?
It may have been picked too late, stored too long, or crossed with another type of corn growing nearby. Pick at the milky stage and eat or chill it right away. Keep different sweet corn types apart or plant them to tassel at different times.
See what else to plant in May or June.
Tomatoes
Peppers
Eggplant
Tomatillos
Ground cherries