When should I plant tomatoes in ZIP 48226?

In ZIP 48226, the main tomatoes target is around May 12, based on the representative Detroit frost station and USDA zone 6b.

When should I start tomatoes seeds indoors in 48226?

Start tomatoes seeds indoors in ZIP 48226 around Mar 24, about 42 days before the May 5 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 48226 planting calendar

When to plant tomatoes in Detroit, MI - Zone 6b

Q: When is the first frost in Detroit?

Detroit (ZIP 48226) has an average first fall frost around Oct 15, leaving about 163 frost-free days.

In ZIP 48226, plant tomatoes around May 12; this uses the Detroit frost station, USDA zone 6b, and tomatoes timing rules.

Your Detroit calendar has a 163-day estimated frost-free season. This estimate uses the representative Detroit frost station, USDA zone 6b, and tomatoes timing rules.

Source: detroit-metro frost station, USDA zone 6b, 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 6b Detroit frost station Michigan State University Extension Updated 2026-06-28

Read the method

Answer first

When to start tomatoes seeds indoors in Detroit

In ZIP 48226, start tomatoes seeds indoors around Mar 24, about 42 days before the May 5 last-frost estimate.

Start tomatoes seeds indoors in Detroit around Mar 24, about 42 days before the May 5 last-frost estimate.

Seed starting schedule

Tomatoes dates for Detroit, MI

Step	Date	How to use it
Start Indoors	March 24, 2026	Start seeds under lights or in a bright indoor seed-starting space.
Transplant Outdoors	May 12, 2026	Move hardened-off seedlings outside after the frost-risk window.

Last frost

When is the last frost in Detroit?

Detroit (ZIP 48226) has an average last spring frost around May 5.

First frost

When is the first frost in Detroit?

The average first fall frost is around Oct 15, giving about 163 frost-free days.

Season map

Tomatoes windows by month

JanFebMarAprMayJunJulAugSepOctNovDec

Start indoors

Mar 24

Transplant

May 12

Harvest

Jul 29

Frost watch

Jul 29

Reminder workflow

Every date has a next action

Start tomatoes indoorsMar 24

Last frost windowMay 5

Transplant tomatoesMay 12

First tomatoes harvest windowJul 29

Last tomatoes sowing targetJul 29

Signal	Value	Why it matters
Last frost estimate	May 5, 2026	Warm-season transplant risk starts falling after this window.
First frost estimate	October 15, 2026	Fall planting counts backward from this date.
Season length	163 days	Longer seasons can support succession crops.
Spacing	18-24 in	Airflow and root space affect yield.
Soil temperature	60 F+	Seeds and transplants stall in cold soil.

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Local data

Why this date changes by ZIP

Detroit frost history and USDA zone 6b shift the safe planting window. GrowZone uses a local representative station instead of one national rule.

Michigan 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

Tomatoes timing notes

Harden seedlings off for a week before transplanting. Tomatoes prefers full sun, 18-24 in spacing, and soil near 60 F+.

For fall, count backward from Oct 15. A conservative last sowing target is around Jul 29.