Oregon · zones 6a–9a
When to plant sweet corn in Oregon.
Sow between Apr 22 to Jul 22 in a typical year, keyed to Oregon's median last frost around Apr 15. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Sweet Corn dates for a typical Oregon season.
Direct sow
Apr 22 to Jul 22
Keyed to the ~Apr 15 last frost. Sow 1.5" deep, 12" apart.
Harvest
~75 days later
~1 lb per plant over ~1 weeks.
Oregon spans more than one climate: Zone 8 is the most common zone, but the state runs 6a to 9a. That's why the planner works from your ZIP code's frost dates, not your zone: mountain and coastal gardens in the same state can be three weeks apart.
Oregon growing notes
A single sweet corn stalk gives back about a pound of usable ear, which is exactly why this state's growing season is built to run the crop twelve times over instead of once.
Deeper seed, tighter spacing, and a crop that needs company
Sweet corn goes into the ground here as seed, sown an inch and a half deep, deeper than the inch or less most other direct-sown vegetables get, since a kernel carries enough stored energy to push a shoot up from that depth. Plants are thinned to 12 inches apart in the row, tight compared to a watermelon vine's 36 inches, but corn does not sprawl the way a vine does; it grows straight up, and the crowding is the point.
That tight spacing only pays off arranged as a block, several short rows set beside each other, not stretched into one or two long rows. Corn is wind-pollinated: the tassel at the top of each stalk sheds pollen that has to drift down and sideways onto the silks of a neighboring plant, and a single skinny row loses most of that pollen to open air before it lands anywhere useful. A block a few rows deep in every direction catches far more of its own pollen. An old, open-pollinated type such as Golden Bantam is worth a look on the cooler, marine side of the state: the edge is in the seed, not the open pollination, since a standard type germinates more reliably in cool soil than the shrunken, low-starch seed of a modern supersweet hybrid bred for a bigger sugar payload.
Two caterpillars, two different parts of the plant
Corn earworm moths lay eggs on fresh silk, and the caterpillar that hatches tunnels down the silk channel into the tip of the ear, concentrating the damage rather than spreading through the ear. Once the silks at that tip have gone from green and fresh to brown and dry, the worst of the feeding pressure has usually passed, since moths lay on fresh green silk and largely stop once it browns. Some gardeners drop a bit of oil onto the silk channel once it browns, smothering a worm already inside without spraying the whole plant.
Fall armyworm attacks a younger plant in a different spot: the whorl of unopened leaves at the stalk's center, before tasseling. The tell is ragged holes across several leaves once they unfurl, lined up in a row from when the leaves were still rolled together, plus moist, sawdust-like droppings inside the whorl. Common rust shows up on the leaves as small, reddish-brown, powdery pustules, usually after humid weather more common west of the Cascades than east of them; on a 75-day crop it reads as more cosmetic than damaging, since the ears are often already filling by the time rust builds up. Aphids cluster in the tassels and on leaf undersides, and ants working a stalk are often the tell that aphids are already there, tending them for the sweet residue they leave behind.
Why twelve small crops beat one big one
A single stalk here hands back around a pound of usable ear, modest for a plant that can stand six feet tall, because a stalk this size usually finishes just one or two ears, not the weeks of repeat picking a vining crop gives back from the same footprint. Volume in this crop comes from how many stalks are growing and how well they are timed, not from any one plant carrying the load.
That is why this state's season has room for roughly twelve separate sowings of corn rather than a single planting. Staggering new blocks every couple of weeks instead of one long row means the whole patch does not silk, ripen, and finish in the same seven days, which would otherwise leave a garden buried in ears for a week and empty for the rest of the summer. Each block needs to be wide enough in both directions to pollinate itself; a long thin ribbon of twelve rounds planted end to end defeats the purpose as surely as a single skinny row would.
In Oregon: watch for
The pests that find sweet corn here.
A middle-length season, about 193 frost-free days, means sweet corn overlaps corn earworm for a stretch each summer. Check plants every week or two and treat early.
Caterpillars feeding down in the tip of the ear.
Organic fix: A few drops of oil on the silk; Bt on the silks.
Clusters on the tassels and upper leaves.
Organic fix: Usually minor; insecticidal soap if heavy.
Fall armyworm
Ragged holes through the unfurling whorl leaves, with sawdust-like droppings down in the funnel.
Organic fix: Check whorls weekly before tassel; Bt or spinosad while the caterpillars are still small.
Cinnamon-brown powdery pustules breaking out on BOTH sides of the same leaf, lower leaves first, darkening as they age.
Organic fix: Water at the ground rather than overhead, and choose resistant varieties next season; sprays are rarely worth it.
Your season math: Oregon gives sweet corn about 193 frost-free days, and it needs roughly 75 days to a first harvest. That fits about 12 re-sown rounds across the season, so you can keep it coming instead of picking once.
Planting sweet corn in Oregon: questions
When should I plant sweet corn in Oregon?+
In a typical Oregon year, sow sweet corn between Apr 22 to Jul 22, keyed to the state's median last frost around Apr 15. Your exact dates shift with your ZIP code and microclimate.
What USDA zone is Oregon?+
Oregon spans zones 6a–9a, mostly zone 8. But frost dates, not zones, set planting time. The free planner uses your ZIP code's actual frost dates.
How many sweet corn plants do I need?+
Depends who you're feeding. The crop page has exact counts per household size, or the free planner does the math for your family in about 60 seconds.