When to plant kohlrabi in Seattle and Tacoma, WA

Plant kohlrabi in the garden in Seattle and Tacoma Mar 15 – Apr 26, either as seeds or as young plants started indoors Feb 1–15. For a fall harvest, plant again Aug 13–27.

Easy Plant seeds or young plants

Why these dates

Seattle and Tacoma's typical last spring frost is March 2. In the west-side valleys, the soil is usually ready for kohlrabi around March 15.

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: Easy
Sun: Full sun
Spacing: Thin to 6 inches apart
Planting depth: ¼ to ½ inch deep
Frost: Handles light frost
First harvest: About 55 days after planting

Step by step

Start seeds indoors Feb 1–15 in trays or small pots under a grow light or in your sunniest window. Or skip this step and buy young plants (starts) at a garden center.
Harden off the young plants: about a week before planting, set them outside for a few hours a day, a little longer each day.
Plant them in the garden Mar 15 – Apr 26, Thin to 6 inches apart. If you plant seeds instead, sow them ¼ to ½ inch deep.
Water deeply once or twice a week rather than a little every day, and mulch once the soil is warm.
Plant again Aug 13–27 for a fall harvest.
Harvest: Cut bulbs at 2 to 3 inches across. Peel off the tough skin and eat raw or cooked.

Varieties that do well here

Kolibri (purple)
Winner
Kossak (large, stores well)

Watch out for

Cabbage worms chew the leaves. Insect netting keeps the white moths from laying eggs.

Pick when the bulb is about tennis-ball size; bigger ones turn woody.

Common questions

When is the last frost in Seattle and Tacoma, WA?

Typically March 2. In 9 years out of 10, frost is over by March 23. These are 1991–2020 NOAA climate normals for Seattle-Tacoma International Airport.

Is it too late to plant kohlrabi in Seattle and Tacoma?

The spring planting window runs through April 26. If you miss it, plant again for fall from August 13 to August 27.

When should I start kohlrabi from seed indoors in Seattle and Tacoma?

February 1 to February 15, which is 6 to 4 weeks before the March 15 planting date. Or buy young plants at a garden center instead.