Kansas · zones 5b–7a
When to plant broccoli in Kansas.
Sow or transplant between Feb 21 to Mar 21 in a typical year, keyed to Kansas's median last frost around Apr 14. A second, fall sowing fits Jul 8 to Aug 17. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Broccoli dates for a typical Kansas season.
1 · Start indoors
Jan 10 to Feb 7
About 6 weeks before set-out. Warm spot, real light.
2 · Set out
Feb 21 to Mar 21
Keyed to the ~Apr 14 last frost. Sow 0.5" deep, 18" apart.
Fall round
Jul 8 to Aug 17
Counted back from the ~Oct 22 first frost.
Harvest
~60 days later
~1.2 lb per plant over ~3 weeks.
Kansas spans more than one climate: Zone 6 is the most common zone, but the state runs 5b to 7a. 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.
Kansas growing notes
Broccoli has to beat a Kansas spring, not just survive it.
Spring whiplash causes buttoning, not the cold itself
Kansas springs swing hard: a 75 degree afternoon can flip into a night in the 30s within 48 hours, and a young broccoli transplant reads that kind of swing as a signal to bolt small rather than grow on schedule. Let a transplant sit through five or more days below 40 degrees before it has ever started to head, whether from a late cold snap right after set-out or from too many weeks stalled root-bound in a small pot, and the plant panics into buttoning: it sets a head the size of a golf ball weeks ahead of schedule and never sizes up past that. Once a plant has buttoned there is no recovery; the fix is always the next transplant, not this one.
That is one reason a lot of experienced Kansas gardeners treat the fall crop as the main event and the spring crop as a bonus round. Fall-set transplants grow through warm weather and finish heading as temperatures ease downward, which flips the risk: cooling weather tightens a head instead of triggering an early, tiny one. If bed space forces a choice between the two windows, give the better soil and the sturdier transplants to the fall planting and treat spring broccoli as practice.
Hollow stem is usually a growth problem, not a mineral one
A stem that grows fast under heavy nitrogen and wide spacing can outrun its own pith, leaving a hollow core the way an overfed tree leaves a soft center. Split a harvested stem lengthwise: a clean white cavity is the growth-rate version, fixed with less nitrogen and tighter spacing next round, not a spray. A cavity stained brown instead of white points to an actual boron shortage, common enough on western Kansas ground over old limestone and caliche even at a pH of 7.5 or higher; that case earns one light foliar spray at golf-ball-size heads, since broccoli's boron window is narrow and an overdose is toxic.
Eastern Kansas sits on old glacial till instead, running a more acidic clay loam that rarely shows hollow stem but stalls broccoli outright below pH 6.0, so a lime test before planting matters just as much there. Whichever soil you are working, dig 2 inches of compost into the bed ahead of transplanting, and on the alkaline western half of the state lean toward the tighter end of the normal spacing range rather than giving plants extra room, since a wide-spaced plant is the one that grows fastest and hollows out.
Scout before you spray, not after
Cabbage worms and loopers, the green caterpillars that leave ragged holes and dark droppings on leaf undersides, are the main summer and fall threat, and the trigger is a share of the bed, not a count on one leaf. Walk 20 plants weekly before heads form: once about half show chewing or a caterpillar, spray Bt. Once curds are visibly forming, tighten that trigger to roughly 1 in 10 plants, since a spray matters more the closer harvest gets. Bt kills only caterpillars and spares pollinators. Flea beetles arrive earliest in the season, shot-holing young transplants before they have leaf area to spare, and a floating row cover left on from transplant day until heads start forming blocks them without any spray at all.
Aphids cluster down inside the developing head itself, which makes them the one pest here that ruins the actual harvest rather than just the leaves, because a head full of dead, sprayed aphids is still a head full of bugs at dinner. A hard blast from the garden hose, aimed up underneath the forming head 2 or 3 days before you plan to cut it, knocks most of the colony loose without bruising the curd, and beats any spray for a crop you are about to eat raw or lightly steamed.
In Kansas: watch for
The pests that find broccoli here.
A middle-length season, about 191 frost-free days, means broccoli overlaps cabbage worms & loopers for a stretch each summer. Check plants every week or two and treat early.
Green caterpillars chewing ragged holes; green droppings.
Organic fix: Handpick, cover with netting, spray Bt.
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.
Seedlings wilt, yellow and stall for no reason; white maggots tunnel the roots.
Organic fix: Row cover before the flies are up, when yellow rocket blooms; rotate the bed.
Your season math: Kansas gives broccoli about 191 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 Kansas: questions
When should I plant broccoli in Kansas?+
In a typical Kansas year, sow broccoli or set out transplants between Feb 21 to Mar 21, keyed to the state's median last frost around Apr 14. There's also a fall window: Jul 8 to Aug 17. Your exact dates shift with your ZIP code and microclimate.
When do I start broccoli seeds indoors in Kansas?+
Start seeds inside about 6 weeks before set-out: roughly Jan 10 to Feb 7 for a typical Kansas season.
What USDA zone is Kansas?+
Kansas spans zones 5b–7a, mostly zone 6. 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.