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Rows of green onion plants growing in a field
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When to plant onions in Tri-Cities (Pasco, Kennewick, Richland), WA

Plant onion sets in Tri-Cities (Pasco, Kennewick, Richland) Mar 20 – Apr 24.

Moderate Plant small onion bulbs (sets)

Why these dates

Tri-Cities (Pasco, Kennewick, Richland)'s typical last spring frost is April 27. As a cool-season crop that handles light frost, this crop doesn't need to wait for that date. In the Columbia Basin and low eastern valleys, though, the soil usually isn't ready to work until about March 20.

Columbia Basin and low eastern valleys. Hot, dry summers and quick spring warm-up. Warm crops go in earlier than west of the Cascades, and irrigation matters more than rain.

Difficulty
Moderate
Sun
Full sun
Spacing
4 inches apart
Planting depth
Sets 1 inch deep, tip just showing
Frost
Handles light frost
First harvest
About 110 days after planting

Step by step

  1. Prepare the bed: loosen the soil and mix in an inch or two of compost.
  2. Plant onion sets Mar 20 – Apr 24, 4 inches apart, sets 1 inch deep, tip just showing.
  3. Water regularly and keep the bed weeded; onions don't compete well.
  4. Harvest: When the tops flop over in late summer, pull the onions and let them dry in a shady, airy spot for two weeks.

Varieties that do well here

  • Walla Walla Sweet
  • Copra (stores well)
  • Redwing

Watch out for

Weeds outcompete onions' thin leaves. Keep the bed weeded and mulched.

Plant as soon as the soil is dry enough to work. Pick long-day varieties for the Northwest.

Common questions

When is the last frost in Tri-Cities (Pasco, Kennewick, Richland), WA?

Typically April 27. In 9 years out of 10, frost is over by May 10. These are 1991–2020 NOAA climate normals for Pasco Tri-Cities Airport.

Is it too late to plant onions in Tri-Cities (Pasco, Kennewick, Richland)?

The spring planting window runs through April 24. Later plantings tend to struggle in summer heat.

How long until I can harvest onions?

About 110 days after planting. When the tops flop over in late summer, pull the onions and let them dry in a shady, airy spot for two weeks.

Also plant in Tri-Cities (Pasco, Kennewick, Richland) around the same time

Planting dates for onions in nearby areas

Full planting calendar for Tri-Cities (Pasco, Kennewick, Richland) · Onions in every city