Herb

When to Plant Basil in Washington

The king of herbs. Basil and tomatoes are best friends in the garden and in the kitchen.

The Short Answer

Growing basil in western Washington is a test of creative microclimate management — the region's cool, cloudy summers are a far cry from basil's Mediterranean homeland. But it's absolutely possible, and the satisfaction of harvesting fresh basil from a Puget Sound garden is proportional to the challenge. Eastern Washington, by contrast, grows basil effortlessly in its hot, sunny, dry conditions.

Washington Frost Dates

Your planting dates depend on which part of Washington you're in. Here are the frost date ranges by region:

Region Zones Last Frost (Spring) First Frost (Fall)
Western Washington (Seattle/Tacoma) 8a, 8b Mar 25 - Apr 15 Oct 25 - Nov 15
Puget Sound 8b, 9a Mar 15 - Apr 5 Nov 1 - Nov 20
Eastern Washington 5b, 6a, 6b, 7a Apr 25 - May 15 Sep 25 - Oct 15
Central Washington 6a, 6b, 7a Apr 20 - May 10 Oct 1 - Oct 20

Basil Planting Schedule for Washington

Western Washington (Seattle/Tacoma) (Zones 8a, 8b)

Average last frost: Mar 25 - Apr 15 · Average first frost: Oct 25 - Nov 15

Start Seeds Indoors
6 wks before frost
Transplant Outside
2 wks after frost
Direct Sow
2 wks after frost

Puget Sound (Zones 8b, 9a)

Average last frost: Mar 15 - Apr 5 · Average first frost: Nov 1 - Nov 20

Start Seeds Indoors
6 wks before frost
Transplant Outside
2 wks after frost
Direct Sow
2 wks after frost

Eastern Washington (Zones 5b, 6a, 6b, 7a)

Average last frost: Apr 25 - May 15 · Average first frost: Sep 25 - Oct 15

Start Seeds Indoors
6 wks before frost
Transplant Outside
2 wks after frost
Direct Sow
2 wks after frost

Central Washington (Zones 6a, 6b, 7a)

Average last frost: Apr 20 - May 10 · Average first frost: Oct 1 - Oct 20

Start Seeds Indoors
6 wks before frost
Transplant Outside
2 wks after frost
Direct Sow
2 wks after frost

Growing Basil in Washington

State-Specific Growing Tips

Western Washington: don't transplant until mid-June when nighttime temperatures are reliably above 50°F. Plant in the warmest spot you can find — south-facing wall, dark-colored containers on a patio, raised beds that warm faster than ground level. Black plastic mulch raises soil temperature. Cover with a cold frame or cloche during June's inevitable cool spells. Despite the challenges, western Washington's dry summers (relative to the East) mean almost zero downy mildew pressure — a genuine silver lining. Eastern Washington: transplant from mid-May and enjoy explosive growth in the hot, dry conditions basil loves.

Recommended Varieties for Washington

Western Washington: Genovese Compact and other small-statured varieties do better than large-leaved types in cool conditions. Thai Basil is more cold-tolerant than Italian basil and produces well in the Puget Sound region. For eastern Washington, grow anything — the hot, dry conditions are ideal. Genovese, Thai, Lemon, Purple — all thrive. WSU Extension's herb growing recommendations address both sides of the state.

Common Challenges in Washington

In western Washington, the challenge is temperature, not disease. Cool nights below 50°F slow growth to a crawl. Slugs attack seedlings in the damp maritime climate. The upside: downy mildew is essentially absent from western Washington's dry summers. In eastern Washington, spider mites in hot, dry conditions are the main pest concern. Japanese beetles are rare in Washington — another Pacific Northwest advantage.

Growing Tips

Pinch off flower buds to keep leaves producing. Harvest from the top down, cutting just above a leaf pair. Succession plant for season-long supply.

Companion Planting

Plant basil alongside these companions for better growth:

Tomatoes Peppers Oregano

Keep basil away from:

Sage

The Bottom Line

Basil can be grown successfully in Washington with proper attention to regional frost dates and local growing conditions. Timing varies across the state — Western Washington (Seattle/Tacoma) gardeners work with a last frost around Mar 25 - Apr 15, while Central Washington sees frost end around Apr 20 - May 10. Choose varieties suited to your region, amend your soil based on its specific needs, and monitor for the pests and diseases most common in your area. For exact dates based on your zip code, use our free planting date finder.

Related Guides

Basil Growing Guide National planting guide with all states Washington Planting Calendar All plants for Washington Basil in Alabama Alabama planting dates Basil in Alaska Alaska planting dates Basil in Arizona Arizona planting dates Basil in Arkansas Arkansas planting dates
Note: All dates are based on NOAA 30-year Climate Normals and represent historical averages, not predictions for any specific year. Always check your local weather forecast before planting frost-sensitive crops. Learn about our data sources.

Last reviewed: March 29, 2026

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