Growing broccoli in zone 3a
(Zone 3a = an average winter low of -40°F to -35°F.)
In USDA zone 3a, the typical last spring frost is May 29 and the first fall frost is September 5. Here is when to plant broccoli against those dates.
Typical timing
Zone 3a planting schedule
Evidence trail
How these dates are built
Sprout applies the cited planting offsets to the typical zone 3a frost anchors. The result is a planning baseline for the zone, not a local weather forecast.
- USDA Plant Hardiness Zone Map, 2023USDA Agricultural Research Service / Oregon State University PRISM Group. Supports the USDA hardiness-zone band.
- U.S. Climate Normals 1991-2020NOAA National Centers for Environmental Information. Supports the median spring and fall freeze dates.
- How to Grow Broccoli in Your GardenUtah State University Extension. Supports indoor seed-starting timing (derived), outdoor transplant timing (direct), and direct-sowing timing (direct).
Method note
Transplant/seed timing (2-3 weeks before last frost), sow-indoors offset (6-7 weeks before planting date, re-expressed against last frost using the transplant window), seed depth 1/4 to 1/2 inch (lower bound stored), spacing 12-18 inches in rows 2-3 feet, buttoning and boron disorder. USU water figure is 1-2 inches/week; the UMN figure is used instead. No fall window stored: USU pins fall maturity only to 'several weeks after the first fall frost', which is not numeric.
These are zone 3a averages
Computed from 17 ZIP codes in zone 3a. Your town's frost dates vary; enter your ZIP for dates built on your nearest weather station.
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Put these dates to work
The plant profile covers spacing, light, water, soil, and source-backed timing details. The growing guide covers preparation, care, and harvest technique.