When should I plant Rosemary in Zone 4b?

Start Rosemary seeds indoors around Feb 20. Transplant outdoors after May 8. Expect first harvest around Aug 6.

What is the last frost date for Zone 4b?

The average last spring frost date for Zone 4b is May 1. The first fall frost averages Oct 5, giving a 157-day growing season.

Can I grow Rosemary in Zone 4b?

Yes. Rosemary needs 90 days to harvest. Zone 4b has a 157-day growing season, which is sufficient.

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🌿 Growing Rosemary in Zone 4b

Zone 4b has cold winters and a moderate growing season. Timing is key for Rosemary in this zone. Last frost: May 1. First frost: Oct 5.

Planting Calendar

Indoor

Outdoor

Harvest

Feb 20Oct 5

Season: May 1 – Oct 5 (157 days)

Zone4b

Last FrostMay 1

First FrostOct 5

Season Length157 days

Days to Harvest90

SunFull Sun

Frost ToleranceLight

Spacing1/sqft (12" apart)

When to Plant Rosemary in Zone 4b

Start Seeds Indoors: Feb 20

Start Rosemary seeds indoors around Feb 20 (10 weeks before last frost). Optimal germination temperature: 70°F. Germinates in 14–28 days.

Transplant Outdoors: May 8

Transplant Rosemary seedlings outdoors after May 8. Wait until soil temperature reaches 55°F. Space plants at 1/sqft (12" apart). Harden off plants for a week before moving outside.

Harvest: Aug 6

First harvest approximately Aug 6 (~90 days from transplant). Continue harvesting until first frost (Oct 5). Rosemary can overwinter in mild climates for continued harvest.

Companion Planting

✅ Beans✅ Carrots✅ Cabbage

Rosemary in Other Zones

1a 1b 2a 2b 3a 3b 4a 4b 5a 5b 6a 6b 7a 7b 8a 8b 9a 9b 10a 10b 11a 11b 12a 12b 13a 13b

Plan Your Rosemary Garden

Track Rosemary from seed to harvest with personalized frost dates, watering recommendations, and companion planting visualization.

Start Free Rosemary Growing Guide