Your broccoli forms broccoli small loose heads when stress hits during the critical head growth stage. Heat stress causes this problem more than anything else in home gardens. High temps tell your plant to rush through its life cycle. The result is tiny premature heads instead of full-sized ones.
I saw this happen during one busy week when I forgot to water my spring broccoli. The plants looked fine but the heads came out loose and barely bigger than golf balls. That drought stress during head formation ruined what should have been my best harvest. Now I set phone reminders for watering days so I never skip again.
Broccoli buttoning happens when plants form tiny heads way too early in their growth. This triggers when your plants face stress before they should be heading. Cold snaps below 50 degrees Fahrenheit, dry periods, or nitrogen shortage can all push young plants to head early. The plant thinks survival is at risk.
Iowa State Extension notes that daytime temps above 86 degrees stop proper heads from forming. Nighttime temps above 77 degrees cause the same problem. Your broccoli head problems often trace back to planting dates. You put heading during hot weather without knowing it.
Broccoli not forming heads at all differs from buttoning. Complete heading failure means your plant never got the cool period it needs. Temps must drop and then stay in the 60-70 degree range for heads to form right. Plants stuck in constant warmth keep growing leaves but never switch to making heads.
Steady moisture prevents many broccoli head problems before they start. Your plants need 1-2 inches of water per week at ground level. Mulch around your plants holds moisture and keeps roots cool. Drip lines or soaker hoses work better than overhead watering.
Nitrogen matters most during early growth before heads start forming. Feed your plants when you transplant and again three weeks later. Broccoli puts out lots of leaves before it makes a head. Those leaves need nitrogen. Starving plants skip leaf growth and make tiny emergency heads.
Timing your planting right solves most broccoli buttoning problems. Spring crops need to head before summer heat arrives. Count back 60-80 days from your first expected hot spell. Fall crops work better because temps drop as your plants mature.
Shade cloth helps if your plants face a heat wave during head formation. A 30-40% shade cover can knock temps down enough to save your crop. Water deeply before and during hot spells. These moves can mean the difference between loose golf balls and tight full-sized heads.
Read the full article: Growing Broccoli: Expert Advice for Home Gardeners
