Rainline Garden

When to plant sweet corn in Portland, OR

Plant sweet corn from seed, directly in the garden in Portland, May 10 – Jun 14.

Moderate Plant seeds in the ground

Why these dates

Portland's typical last spring frost is March 13. Frost kills sweet corn, and warm-season crops also need warm soil. Soil here stays cold for weeks after the last frost, so planting waits until about May 10.

West-side valleys. The Willamette Valley, Puget Sound and southern Oregon valleys. Long frost-free seasons, but soil stays cold and wet into May, so warm crops wait for warm soil, not just the last frost.

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

Step by step

  1. Prepare the bed: loosen the soil and mix in an inch or two of compost.
  2. Plant seeds May 10 – Jun 14, 1 inch deep, 10 inches apart in a block of short rows.
  3. Keep the soil evenly moist until sprouts appear, which can take one to three weeks in cool soil.
  4. Harvest: Ready about three weeks after the silks appear, when the silks are brown and the kernels squirt milky juice.

Varieties that do well here

  • Early Sunglow
  • Bodacious
  • Golden Bantam

Watch out for

Crows pull up sprouting seeds. Cover the bed with netting or row cover until plants are 4 inches tall.

Plant in blocks of at least four short rows, not one long row, for good pollination.

Common questions

When is the last frost in Portland, OR?

Typically March 13. In 9 years out of 10, frost is over by April 1. These are 1991–2020 NOAA climate normals for Portland International Airport.

Is it too late to plant sweet corn in Portland?

The spring planting window runs through June 14. Later plantings may not have time to produce before the first fall frost, which usually arrives around November 19.

How long until I can harvest sweet corn?

About 80 days after planting. Ready about three weeks after the silks appear, when the silks are brown and the kernels squirt milky juice.

Also plant in Portland around the same time

Planting dates for sweet corn in nearby areas

Full planting calendar for Portland · Sweet corn in every city