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Plant diseases
Loose sprouts
Also called fluffy sprouts (UK and USA).
Illustration
Brussels sprouts that open into loose, leafy tufts instead of firm, tight buttons, most often because they formed in hot weather, grew slowly in poor soil, or are an older, non-hybrid kind. Growing F1 hybrid kinds in good soil, keeping them growing steadily and timing them to form in cool weather give firm sprouts.
How to spot it
- Sprouts that are open and leafy, like tiny loose cabbages, instead of tight, firm buttons.
- Often all the way up the stem, on plants that grew slowly or in poor soil.
- Common where the sprouts formed in hot weather, which also makes them bitter.
- Common in older, non-hybrid kinds, and in plants grown from saved seed.
Easily confused with
Bolting
The sprouts and the top stretch into tall shoots with yellow flowers, usually as the weather warms in spring.
Aphids
Colonies of small grey, waxy insects tucked between the sprout leaves and under the big leaves.
Club root
Stunted plants that wilt on warm days, with swollen, distorted roots.
Where it's a problem
- Worldwide: Common wherever sprouts form in warm weather or poor soil. Not regulated.
- United Kingdom: The RHS says the usual cause is poor soil, slow growth and especially non-hybrid kinds, and that loose planting isn't the direct cause.
- United States: Extension services most often blame sprouts that form in hot weather, and advise timing plants so the sprouts form in cool autumn weather.
What to do
- Grow F1 hybrid kinds: they're the only ones that can be relied on for firm sprouts.
- Plant into good, fertile soil. Tread it firm before planting, and firm each plant in.
- Time sowing so the sprouts form in cool autumn and winter weather, not in summer heat.
- Water in dry spells so growth never stalls.
- Stake tall plants and draw soil up around the stems before windy weather, so the roots aren't rocked loose.
- Pick from the bottom up, when the sprouts are walnut-sized, firm and tightly closed.
Spraying won't help: loose sprouts come from the kind grown, the soil and the weather, not an infection. Official guides prevent them with hybrid kinds, good soil and timing.
Vegetables it affects
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Sources (5, from RHS, University of Illinois Extension, University of Missouri IPM and others)
- RHS: How to grow Brussels sprouts · Brussels sprouts problems
- University of Illinois Extension: Brussels sprouts
- University of Missouri IPM: Brussels sprouts prolong fall harvest
- Iowa State University Extension: Growing Brussels sprouts in the home garden
Facts checked Wednesday 28 October 2026. General guidance only: follow your local council, agency and product label.