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Zone 3B Vegetable Planting Calendar

When can you plant in Zone 3B? In Zone 3B, outdoor sowing opens with cool-season crops like Lettuce and Spinach in April, and warm-season crops like Tomato follow after the ~May 25 last frost. The season runs about 113 frost-free days, until ~September 15. The calendar below scores all 35 crops month by month.

Scored per crop from your zone's frost dates, each crop's days-to-maturity, and typical soil temperatures — honestly, including when not to plant.

A zone caveat: USDA zones reflect winter lows, not summer heat — this calendar is a zone-level guide. For timing tuned to your exact zip code, sun, and soil, get your free AI garden plan.

Last frost (50/50 date)

~May 25

First frost (50/50 date)

~September 15

A single frost date is a coin flip dressed up as a fact: these are the 50/50 dates, and about half of years see frost past them. Across 4,330 NOAA stations, frost odds typically stay near 1 in 3 for about a week past the date and don't drop below 1 in 10 until roughly 16 days past it — cautious growers wait those two-plus weeks; gamblers plant on the date and keep row cover handy. The free AI plan reads the real percentile dates for your zip and lets you pick your risk.

When to Start Seeds Indoors vs. Direct Sow in Zone 3B

In Zone 3B, start Onion, Rosemary, Eggplant and other transplants indoors 5–10 weeks before your ~May 25 last frost, then set them out once it passes. Arugula, Bean, Beet and the other direct-sow crops go straight into the bed. Exact indoor start dates for every crop are below.

Planting a fall garden? Count the indoor weeks back from your transplant date instead of the spring frost — the free AI plan's prep runway computes that per plant, including hardening-off days.

Zone 3B Planting FAQ