When to Plant Broccoli
Planting Window - Start indoors + transplant
- Start indoors
- 6-8 weeks before last frost
- Transplant outdoors
- 2-3 weeks before last frost
| USDA Zone | Typical Window |
|---|---|
| Zone 5 and colder | Transplant April (summer harvest), plus July (fall) |
| Zone 6-7 | Transplant March, plus August |
| Zone 8 and up | Fall-through-winter crop |
Broccoli is a cool-season brassica, genuinely frost-hardy once established, but it carries a specific timing risk most warm-season transplants don't: a young plant exposed to a prolonged cold snap can be triggered into "buttoning" - forming a small, premature head far too early instead of developing into a full-sized one.
Starting Seeds Indoors
Start broccoli seed indoors 6-8 weeks before your zone's average last frost date. Unlike tender crops, broccoli seedlings tolerate a fair amount of cool weather, but very young seedlings (under about three weeks old) exposed to a sustained cold snap are the ones most at risk of buttoning later, so timing the start date to avoid transplanting unusually small, young seedlings into an early cold spell matters more than it does for hardier or more mature transplants.
Transplanting Outdoors
Broccoli transplants go into the garden roughly two to three weeks ahead of your last frost date - it handles a light frost well past the seedling stage, and getting it settled in while temperatures are still cool supports strong head development before summer heat arrives, which can push the plant toward flowering (bolting) before the head is ready to harvest.
Fall Crops Are Often More Reliable Than Spring Ones
Many experienced gardeners consider fall-planted broccoli the more forgiving of the two windows: a fall crop matures into cooling temperatures rather than racing against rising spring heat, which reduces both the buttoning risk from an early cold snap and the bolting risk from a late heat wave - the plant is heading into more stable, favorable conditions either way.
Purple Sprouting Types Run a Different Calendar
Purple sprouting broccoli, a distinct type from the familiar green-headed kind, is typically planted in mid-to-late summer specifically to overwinter and produce its harvest of small spears the following spring - a genuinely different planting and harvest calendar from standard broccoli, closer in spirit to overwintering onions or garlic than to a single-season crop.
Side Shoots Extend the Harvest
Cutting the main central head doesn't end a broccoli plant's productivity - most varieties continue producing smaller side shoots from the leaf joints for weeks afterward, which is worth factoring into planning, since a broccoli bed can keep producing well past the date the main harvest is picked.
Zone boundaries follow the USDA Plant Hardiness Zone Map (2023 revision); frost windows reflect NOAA/NCEI climate normals. Both are typical historical ranges, reviewed annually - not a forecast or a guarantee for any single year. See Methodology & Sources.
Frequently Asked Questions
What does it actually look like when broccoli "buttons"?
A buttoned plant forms a tiny head, often just an inch or two across, far earlier and smaller than a normal harvest-ready head - once this happens there's no fixing it, the plant has already committed to flowering on a miniature scale, which is why avoiding the cold-stress trigger in young seedlings matters more than trying to correct it after the fact.
Does leaving the plant in the ground for weeks of side-shoot production make it more vulnerable to disease than pulling it right after the main harvest?
A little - a plant left standing longer has more time to accumulate the usual brassica pressures, cabbage worms especially, so keeping row cover or pest monitoring going through the side-shoot period matters more than it would for a crop pulled immediately. That small added exposure is generally worth trading for the extra harvest, but it isn't a completely free extension.
Does purple sprouting broccoli have the same buttoning risk from a cold snap that young standard broccoli transplants do?
Not in the same way, since the timing is so different - purple sprouting broccoli is started as a summer seedling growing through late-summer heat rather than early spring's lingering cold, so the specific cold-snap-on-a-tiny-transplant trigger described for standard broccoli isn't really the relevant risk here. Heat stress while it's small and getting established is the bigger concern for purple sprouting broccoli instead, which argues for a bit of afternoon shade during its first few weeks in a hot climate.