Cauliflower and Dill
Beneficial Pair — Good Match
Umbel-flowering plants supporting parasitic wasp and hoverfly populations that prey on caterpillar pests is genuinely documented in beneficial-insect research, which is why this rates higher than most pest-masking claims on this site. What's less certain is the exact scale of protection a home garden's few dill plants provide to a specific cauliflower crop.
Mechanism: Pollinator / Beneficial-Insect Attraction
Dill's umbel flowers draw parasitic wasps and hoverflies whose larvae prey on cabbageworms and other caterpillar pests - a documented beneficial-insect habitat effect. For cauliflower specifically, that matters more than it might for a leafy brassica, since a cabbageworm boring into a forming curd contaminates the one part of the plant you're actually harvesting, rather than just damaging an outer leaf you'd trim away anyway.
Dill's role near brassicas usually gets described in general terms - beneficial insects, fewer caterpillars - but cauliflower is a case where that benefit has an unusually concrete payoff, because of what a cabbageworm actually ruins if it gets past the outer leaves.
Why the Curd Changes the Stakes
A cabbageworm chewing on a loose leaf of kale or collards is an annoyance you can trim around. The same pest working its way into a tight, developing cauliflower curd is a different problem entirely - the curd is the entire harvest, and once a worm or its frass gets inside those tight florets, the head is often unsalvageable for fresh eating. Dill's role in drawing in the parasitic wasps and hoverflies that prey on cabbageworm larvae is worth taking more seriously here than on a crop where pest damage is just cosmetic.
Spacing
Dill's 12-15 inch spacing fits at the outer edge of cauliflower's wide 18-24 inch spacing without crowding the developing head - let dill flower rather than harvesting it for leaves if the beneficial-insect effect is your priority, since it's the flowers doing the work here.
Watch For
Cauliflower's forming curd is genuinely more vulnerable to pest damage becoming a real quality problem than most brassica crops, since a worm or its frass inside the tight curd is far harder to rinse out than damage to a loose kale or collard leaf - keep monitoring for cabbageworms directly on the head even with dill nearby, since the beneficial-insect effect reduces but doesn't eliminate pest pressure.
Frequently Asked Questions
Does dill actually stop cabbageworms from reaching my cauliflower?
Not completely - it supports predator and parasite populations that reduce cabbageworm numbers over time, but it isn't a barrier. Keep checking the developing head directly and handpick any worms you find, especially once the curd starts forming.