Hawaii · zones 12a–12a
When to plant broccoli in Hawaii.
Sow or transplant between Nov 10 to Dec 8 in a typical year, keyed to Hawaii's median last frost around Jan 1. A second, fall sowing fits Sep 16 to Oct 26. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Broccoli dates for a typical Hawaii season.
1 · Start indoors
Sep 29 to Oct 27
About 6 weeks before set-out. Warm spot, real light.
2 · Set out
Nov 10 to Dec 8
Keyed to the ~Jan 1 last frost. Sow 0.5" deep, 18" apart.
Fall round
Sep 16 to Oct 26
Counted back from the ~Dec 31 first frost.
Harvest
~60 days later
~1.2 lb per plant over ~3 weeks.
Hawaii spans more than one climate: Zone 12 is the most common zone, but the state runs 12a to 12a. That's why the planner works from your ZIP code's frost dates, not your zone: mountain and coastal gardens in the same state can be three weeks apart.
Hawaii growing notes
Of the five cool-season crops here, broccoli is most likely to lose an outright fight with sea-level heat, and the honest answer is to treat a coastal planting as a test.
A head has to close under pressure a leaf never faces
A transplant crop at about 18 inches apart and a half inch deep, broccoli aims for a first harvest around 60 days out and a modest return of about 1.2 pounds per plant, mostly from the one central head plus whatever smaller side shoots follow. Unlike kale, which keeps producing leaves indefinitely, broccoli has one structure deciding whether the harvest was worth the bed space: the head has to gather into a tight, dense cluster of unopened buds, and that gathering runs on sustained cool weather. Take the cool weather away and the head comes in uneven, the buds sitting in loose clusters instead of packing tight.
Watch the head as it forms rather than trusting a mainland timeline: one staying tight and dense as the days pass is doing what it should, while one going patchy, with gaps opening between the bud clusters and some beads swelling ahead of others, has gone as far as warm weather will let it. Either way that head is done and worth cutting, because a head that has opened up does not close back.
Two windows on the calendar, one round in practice, and why that costs more here than for kale
Like kale, broccoli is marked with both a spring and a later window open, but only one planting round scheduled, since the climate doesn't swing enough to treat them as different plantings. Where broccoli differs from kale is what a single missed shot costs: kale forgives a rough patch by making more leaves, but broccoli's whole harvest rides on that one head, so a round that comes in loose and uneven has no second flush to make up for it.
This is exactly the kind of crop where elevation matters more than technique. A garden with cooler ground, upcountry on Maui or up the higher slopes of the Big Island, has a real edge here that a coastal yard does not, simply because the head needs sustained cool weather to gather tightly and elevation is what supplies that. A coastal planting is still worth trying, but going in expecting a trial rather than a sure thing is the honest way to run it.
The same five pests, but every one threatens the one thing this plant only grows once
With no winter to interrupt them, cabbage worms and loopers stay active on broccoli here, and that pressure lands on the one structure the whole planting is aimed at: feeding that reaches the developing head ruins the harvest outright. Check the crown and the forming head directly, looking for caterpillars or the ragged holes and dark droppings they leave; a worm chewing into the head is worth removing by hand right away. Flea beetles hit hardest at the transplant stage, peppering small leaves with a scatter of tiny holes, and a floating row cover through the first few weeks protects the seedling.
Black rot and Chinese rose beetle both need catching early, before either gets ahead of the plant. Black rot shows as a yellow, V-shaped wedge cutting in from the leaf edge with blackened veins inside it; a transplant already showing this is worth replacing rather than setting out. Chinese rose beetle does its feeding after sundown and burrows back underground by the time it is light out, so most growers only ever see the damage: leaves eaten into connected lace between the veins by morning. A flashlight check after dark, beetles dropped by hand into soapy water, catches it out feeding, and the same water in a shallow dish under a dim light works as a trap, since this beetle moves toward low light, away from a bright one. Aphids also show up, clustering under the youngest leaves near the head; a hard water spray knocks them back before they spread onto the head itself.
In Hawaii: watch for
The pests that find broccoli here.
With about 364 frost-free days, broccoli spends longer in the ground here than in most of the country, which widens the window in which cabbage worms & loopers can find it. Scout weekly from midseason and act on the first signs.
Green caterpillars chewing ragged holes; green droppings.
Organic fix: Handpick, cover with netting, spray Bt.
Chinese rose beetle
Leaves chewed to lace between the veins, with no insect in sight by day.
Organic fix: Go out after dark with a jar of soapy water and pick them off, or hang a dim light over a soapy tray to trap them.
Gray-green clusters tucked into the leaf folds.
Organic fix: Blast with water, then insecticidal soap.
Tiny holes peppering the young leaves.
Organic fix: Row cover from day one; diatomaceous earth.
Black rot
Yellow V-shaped wedges cutting in from the leaf edge, veins blackening inside.
Organic fix: Pull infected plants, water at the base, keep brassicas out of that bed 3 years.
Your season math: Hawaii gives broccoli about 364 frost-free days, and it needs roughly 60 days to a first harvest. It's a one-planting crop, so time that single sowing well.
Planting broccoli in Hawaii: questions
When should I plant broccoli in Hawaii?+
In a typical Hawaii year, sow broccoli or set out transplants between Nov 10 to Dec 8, keyed to the state's median last frost around Jan 1. There's also a fall window: Sep 16 to Oct 26. Your exact dates shift with your ZIP code and microclimate.
When do I start broccoli seeds indoors in Hawaii?+
Start seeds inside about 6 weeks before set-out: roughly Sep 29 to Oct 27 for a typical Hawaii season.
What USDA zone is Hawaii?+
Hawaii spans zones 12a–12a, mostly zone 12. But frost dates, not zones, set planting time. The free planner uses your ZIP code's actual frost dates.
How many broccoli plants do I need?+
Depends who you're feeding. The crop page has exact counts per household size, or the free planner does the math for your family in about 60 seconds.