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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 ZIP region, 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 region and lets you pick your risk.

Zone 3B Month by Month

The same verdicts as the grid, read as a to-do list. Temperatures are the zone-level model this calendar scores against — your bed's soil thermometer overrules them.

1. January soil ~25°F · highs ~29°F · 0 of 35 crops in a good window
   Nothing plants this month — order seed, build soil, and plan the beds.
2. February soil ~27°F · highs ~33°F · 0 of 35 crops in a good window
   Nothing plants this month — order seed, build soil, and plan the beds.
3. March soil ~34°F · highs ~42°F · 0 of 35 crops in a good window
   Start indoors: Onion, Pepper, Eggplant, Rosemary, Thyme, Oregano, Chives, and Parsley. Nothing goes in the ground outdoors.
4. April soil ~44°F · highs ~54°F · 20 of 35 crops in a good window
   Opens: Lettuce, Spinach, Kale, Swiss Chard, Arugula, and Carrot and 14 more. Start indoors: Lettuce, Kale, Swiss Chard, Broccoli, Cabbage, Cauliflower, Tomato, and Basil.
5. May soil ~54°F · highs ~66°F · 20 of 35 crops in a good window
   Start indoors: Zucchini and Cucumber. Risky: Corn (short-season varieties only). Nothing new opens or closes.
6. June soil ~61°F · highs ~75°F · 26 of 35 crops in a good window
   Opens: Tomato, Basil, Zucchini, Cucumber, Bean, and Sunflower. Last good month for: Potato, Tomato, Basil, Zucchini, Cucumber, and Bean and 2 more. Risky: Pepper, Eggplant, and Corn (short-season varieties only).
7. July soil ~64°F · highs ~79°F · 18 of 35 crops in a good window
   Last good month for: Lettuce, Spinach, Kale, Swiss Chard, Carrot, and Beet and 6 more. Risky: Potato (finishes just ahead of first frost); Parsley (last sowing before the window closes).
8. August soil ~61°F · highs ~75°F · 6 of 35 crops in a good window
   Last good month for: Arugula. Risky: Lettuce, Kale, Swiss Chard, and Carrot and 4 more (finishes just ahead of first frost); Spinach and Cilantro (last sowing before the window closes).
9. September soil ~54°F · highs ~66°F · 6 of 35 crops in a good window
   Opens: Garlic. Last good month for: Radish. Risky: Arugula (finishes just ahead of first frost).
10. October soil ~44°F · highs ~54°F · 5 of 35 crops in a good window
    Last good month for: Garlic, Rosemary, Thyme, Oregano, and Chives.
11. November soil ~34°F · highs ~42°F · 0 of 35 crops in a good window
    Risky: Garlic (shoulder of the garlic window).
12. December soil ~27°F · highs ~33°F · 0 of 35 crops in a good window
    Nothing plants this month — order seed, build soil, and plan the beds.

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.

How Much Fits in a Zone 3B Season

• 18 of 35 crops have four or more good planting months in Zone 3B.
• Widest windows: Chives (7 months), Oregano (7 months), Rosemary (7 months).
• Tightest windows: Basil (1), Bean (1), Cucumber (1), Sunflower (1), Tomato (1), Zucchini (1) and 1 more — plant these on the first good month, not the last.
• Short-season varieties only: Pepper, Eggplant, and Corn — the standard varieties don't fit; pick the fastest days-to-maturity on the rack.
• Not recommended in Zone 3B: Cantaloupe, Okra, Pumpkin, Sweet Potato, and Watermelon — no month scores better than off-season.
• Good months per crop in Zone 3B: Chives 7 · Oregano 7 · Rosemary 7 · Thyme 7 · Radish 6 · Arugula 5 · Beet 4 · Broccoli 4 · Cabbage 4 · Carrot 4 · Cauliflower 4 · Cilantro 4 · Kale 4 · Lettuce 4 · Onion 4 · Peas 4 · Spinach 4 · Swiss Chard 4 · Parsley 3 · Potato 3 · Garlic 2 · Basil 1 · Bean 1 · Cucumber 1 · Sunflower 1 · Tomato 1 · Zucchini 1 · Cantaloupe 0 · Corn 0 · Eggplant 0 · Okra 0 · Pepper 0 · Pumpkin 0 · Sweet Potato 0 · Watermelon 0

Zone 3B Planting FAQ