USDA Zone 4a — Garden & Frost Dates for Bismarck, ND (58501)
This is the local garden report for ZIP code 58501 (Bismarck, ND). It pairs the official USDA 2023 hardiness zone with NOAA-based frost dates so you can plan seeds, transplants, and fall crops with real numbers for your neighborhood.
What does zone 4a mean for Bismarck?
Zone 4a is the USDA Plant Hardiness Zone for ZIP 58501, based on the 30-year (1991-2020) average annual extreme minimum winter temperature. Perennial plants labeled for zone 4a or lower should survive a typical winter here. The last spring frost averages 05-12 and the first fall frost averages 09-22, giving roughly 133 frost-free growing days — the window that most vegetables need to go from seed to harvest.
Start your Bismarck planting calendar
This calendar is pre-loaded with the exact frost dates for ZIP 58501 (Bismarck, ND) — more precise than a state-wide average. Pick a crop and print the plan.
In this ZIP (typical zone 3–4), last frost ≈ May 12, first frost ≈ Sep 22 (133-day season), your Tomato plan:
Month-by-month (this ZIP, 2026)
| Month | Action |
|---|---|
| Jan | — |
| Feb | — |
| Mar | Start indoors |
| Apr | — |
| May | Sow · Transplant |
| Jun | — |
| Jul | — |
| Aug | Harvest |
| Sep | — |
| Oct | — |
| Nov | — |
| Dec | — |
Start indoors 6 weeks before last frost; transplant after soil warms. Zones 3–13 suitable. Dates are typical; confirm with your county extension and watch the 10-day forecast.
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