When should I plant basil in ZIP 97204?

In ZIP 97204, the main basil target is around Apr 11, based on the representative Portland frost station and USDA zone 9a.

When should I start basil seeds indoors in 97204?

Start basil seeds indoors in ZIP 97204 around Feb 25, about 35 days before the Apr 1 last-frost estimate.

Is this a guaranteed planting date?

No. GrowZone uses frost-date estimates, hardiness zones, and crop timing rules for planning. Local microclimates and current weather can shift the right date.

ZIP 97204 planting calendar

When to plant basil in Portland, OR - Zone 9a

Q: When is the first frost in Portland?

Portland (ZIP 97204) has an average first fall frost around Nov 10, leaving about 223 frost-free days.

In ZIP 97204, plant basil around Apr 11; this uses the Portland frost station, USDA zone 9a, and basil timing rules.

Your Portland calendar has a 223-day estimated frost-free season. This estimate uses the representative Portland frost station, USDA zone 9a, and basil timing rules.

Source: portland-intl frost station, USDA zone 9a, last updated 2026-06-28. Verify locally before planting high-value crops because microclimates, current weather, and yard exposure can move the safe date.

USDA zone 9a Portland frost station Oregon State University Extension Updated 2026-06-28

Read the method

Answer first

When to start basil seeds indoors in Portland

In ZIP 97204, start basil seeds indoors around Feb 25, about 35 days before the Apr 1 last-frost estimate.

Start basil seeds indoors in Portland around Feb 25, about 35 days before the Apr 1 last-frost estimate.

Seed starting schedule

Basil dates for Portland, OR

Step	Date	How to use it
Start Indoors	February 25, 2026	Start seeds under lights or in a bright indoor seed-starting space.
Transplant Outdoors	April 11, 2026	Move hardened-off seedlings outside after the frost-risk window.
Direct Sow	April 11, 2026	Sow seed outside when the crop and soil can handle the window.

Last frost

When is the last frost in Portland?

Portland (ZIP 97204) has an average last spring frost around Apr 1.

First frost

When is the first frost in Portland?

The average first fall frost is around Nov 10, giving about 223 frost-free days.

Season map

Basil windows by month

JanFebMarAprMayJunJulAugSepOctNovDec

Start indoors

Feb 25

Direct sow

Apr 11

Transplant

Apr 11

Harvest

Jun 15

Frost watch

Sep 6

Reminder workflow

Every date has a next action

Start basil indoorsFeb 25

Last frost windowApr 1

Direct sow basilApr 11

Transplant basilApr 11

First basil harvest windowJun 15

Last basil sowing targetSep 6

Signal	Value	Why it matters
Last frost estimate	April 1, 2026	Warm-season transplant risk starts falling after this window.
First frost estimate	November 10, 2026	Fall planting counts backward from this date.
Season length	223 days	Longer seasons can support succession crops.
Spacing	10-12 in	Airflow and root space affect yield.
Soil temperature	65 F+	Seeds and transplants stall in cold soil.

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Local data

Why this date changes by ZIP

Portland frost history and USDA zone 9a shift the safe planting window. GrowZone uses a local representative station instead of one national rule.

Oregon State University Extension is the kind of local source to verify against when a crop is expensive, weather is unusual, or your yard has a cold pocket.

Crop note

Basil timing notes

Pinch the growing tips early for fuller plants. Basil prefers full sun, 10-12 in spacing, and soil near 65 F+.

For fall, count backward from Nov 10. A conservative last sowing target is around Sep 6.