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When to Start Broccoli Seeds

Dates to start broccoli indoors, harden off and plant out for your ZIP code or zone.

Tomato and pepper seedlings in trays under an LED grow light

Broccoli planting dates by zone

At the average last frost date for each USDA half-zone (the median across its ZIP codes, NOAA 1991 to 2020 normals). Enter your ZIP code below for your own dates.

ZoneLast frostStart indoorsTransplantSow outdoors
3aMay 28Apr 16 to Apr 30May 7 to May 14May 7 to May 14
3bMay 17Apr 5 to Apr 19Apr 26 to May 3Apr 26 to May 3
4aMay 13Apr 1 to Apr 15Apr 22 to Apr 29Apr 22 to Apr 29
4bMay 8Mar 27 to Apr 10Apr 17 to Apr 24Apr 17 to Apr 24
5aMay 4Mar 23 to Apr 6Apr 13 to Apr 20Apr 13 to Apr 20
5bMay 1Mar 20 to Apr 3Apr 10 to Apr 17Apr 10 to Apr 17
6aApr 29Mar 18 to Apr 1Apr 8 to Apr 15Apr 8 to Apr 15
6bApr 23Mar 12 to Mar 26Apr 2 to Apr 9Apr 2 to Apr 9
7aApr 16Mar 5 to Mar 19Mar 26 to Apr 2Mar 26 to Apr 2
7bApr 6Feb 23 to Mar 9Mar 16 to Mar 23Mar 16 to Mar 23
8aMar 29Feb 15 to Mar 1Mar 8 to Mar 15Mar 8 to Mar 15
8bMar 18Feb 4 to Feb 18Feb 25 to Mar 4Feb 25 to Mar 4
9aMar 3Jan 20 to Feb 3Feb 10 to Feb 17Feb 10 to Feb 17
9bFeb 2Dec 22 to Jan 5Jan 12 to Jan 19Jan 12 to Jan 19
10aJan 16Dec 5 to Dec 19Dec 26 to Jan 2Dec 26 to Jan 2
10brareby seasonby seasonby season
Your location

Zone medians. Your ZIP code gives the dates of your nearest weather station.

Frost risk

Half of years still get a frost after the spring date, and half get the first fall frost before the fall date.

Frost dates at three risk levels
AverageSaferSafest
Last spring frostApr 23Apr 30May 9
First fall frostOct 22Oct 16Oct 7
Crops (1 selected)

Start your first seeds indoors

Mar 12broccoli

Average frost dates: last Apr 23, first Oct 22 (zone 6b).
Season
Spring seed starting schedule
CropStart indoorsHarden offTransplantSow outdoorsNotes
BroccoliHardyMar 12 to Mar 26Mar 26 to Apr 1Apr 2 to Apr 9Apr 2 to Apr 9Indoors 4 to 6 wk before last frost. Transplant 2 to 3 wk before last frost. Sow outdoors 2 to 3 wk before last frost. Sprouts in 3 to 10 days, best at 80°F soil. Pot up at the first true leaves. The published dates leave little time indoors: sow at the early end.

How to start seeds indoors

Light
Give seedlings 14 to 18 hours of light a day on a timer, with fluorescent or LED fixtures 2 to 6 in above the leaves. Raise the lights as the plants grow.
Clemson HGIC: 16 to 18 hours, tubes 2 to 4 in above. UMD Extension: 14 to 16 hours, 2 to 6 in.
Seed starting mix
Use a sterile, soilless mix, never garden soil. To mix your own, combine equal parts by volume of fine pine bark, sphagnum peat moss and perlite.
NC State Extension Gardener Handbook; Clemson HGIC.
Sowing and warmth
Sow two or three seeds per cell and keep the strongest seedling. A mix temperature of 65 to 75°F germinates most vegetables; after they sprout, 55 to 60°F nights and 65 to 70°F days keep them stocky.
UMD Extension.
Potting up
Move seedlings into larger pots shortly after the first true leaves appear, while they are small and recover quickly.
UMD Extension; Clemson HGIC (one or two sets of true leaves).
Hardening off
Start two to three weeks before transplanting, once plants are about 3 in tall: set them outdoors by day, bring them in before sundown, and give them more direct sun each day. Skip days below 45°F or with strong wind.
Clemson HGIC: 2 to 3 weeks. NC State: at least 2 weeks, not below 45°F.

When to start broccoli seeds

Start broccoli seeds indoors 4 to 6 weeks before your last frost and set the plants out 2 to 3 weeks before it, as University of Illinois Extension and Utah State University Extension time it. You can also sow straight into the garden in that same window, 2 to 3 weeks before the frost date. Broccoli is hardy to about 28°F, so it goes out while tomato seedlings are still indoors.

Seed sprouts in 3 to 10 days. The crop's germination figures put the best soil temperature at 80°F, with 40°F as the lowest that works, so an indoor start in a warm room comes up fastest.

Example dates by zone

At the average (50%) frost dates for each half-zone, from NOAA's 1991 to 2020 normals:

ZoneLast frostStart indoorsHarden offTransplant or sow outdoors
5bMay 1Mar 20 to Apr 3Apr 3 to Apr 9Apr 10 to Apr 17
7aApr 16Mar 5 to Mar 19Mar 19 to Mar 25Mar 26 to Apr 2
9aMar 3Jan 20 to Feb 3Feb 3 to Feb 9Feb 10 to Feb 17

Enter your ZIP code in the planner for dates from your nearest weather station; a city can be a week or more ahead of its zone median.

Why the planner says sow at the early end

The two published windows overlap. Counting 4 to 6 weeks back from the frost for sowing, and 2 to 3 weeks back for transplanting, leaves between 1 and 4 weeks indoors, and in zone 5b only about a week to harden off. Clemson Extension's seed starting table allows 5 to 7 weeks from sowing to setting out for broccoli. So the planner flags broccoli: sow on the first day of the indoor window, which gives the seedlings 3 to 4 weeks, or sow directly in the bed on the transplant dates and skip the indoor step.

Clemson also recommends two to three weeks of hardening off, and the overlap leaves broccoli about one. That is a second reason to sow on the early date, or to direct sow.

Season length is not a concern

Colorado State University Extension counts about 65 days from transplanting to harvest. Even in zone 4b, plants set out Apr 17 to Apr 24 have 167 days before the average Oct 1 frost. The real limit is heat: heads turn loose and bitter in summer, so aim to harvest before the hottest weeks.

A fall crop

Virginia Cooperative Extension's planting table lists more fall than spring plantings of broccoli. The crop records here have no fall sowing weeks for broccoli, so the planner shows spring dates only; check a local extension calendar for your fall window.

Space the transplants with the broccoli spacing calculator, and see every crop's dates for your area in the seed starting calculator or on the zone 6 seed starting page.