Cauliflower and Nasturtium
Beneficial Pair — Good Match
Nasturtium's aphid preference over brassica foliage is one of the better-documented trap-crop claims on this site. The added stakes for cauliflower specifically - aphids embedded in a curd being hard to remove - are a straightforward practical observation rather than something requiring its own trial.
Mechanism: Trap Cropping
Nasturtium's documented preference for aphids over brassica foliage applies to cauliflower the same way it does to any brassica, but the practical stakes differ: aphids that settle into the tight, developing florets of a cauliflower curd are notoriously difficult to rinse out completely, unlike aphids on a flat, loose leaf that wash off easily. Diverting aphid colonies onto nasturtium before they reach that stage matters more here than on a leafy brassica where the same pest is mostly cosmetic.
This is one of several nasturtium-and-brassica trap-crop pairings on this site, but cauliflower raises the practical stakes in a way that's worth calling out specifically rather than treating it the same as a leafy green like kale or collards.
A Curd Is Much Harder to Clean Than a Leaf
Rinsing aphids off a flat kale leaf is straightforward. Aphids that settle into the tight, folded florets of a developing cauliflower curd are a genuinely different problem - water doesn't reach into those gaps easily, and a heavily infested head can be difficult to make appetizing again even after washing. That's the real argument for taking this particular trap-crop pairing seriously: the payoff for keeping aphids off cauliflower specifically is bigger than the same effort spent protecting a crop where the damage just gets trimmed away.
Spacing
Plant nasturtium at cauliflower's outer edge, working with its 18-24 inch spacing, rather than directly under the developing head - the goal is intercepting aphids before they migrate toward the curd, not competing for the same soil the cauliflower's roots need.
Watch For
Check the developing curd directly and often once it starts forming, even with nasturtium nearby - the trap crop reduces the number of aphids reaching the cauliflower, but any that do get established inside the tight florets before you notice can be genuinely difficult to clean out at harvest.
Frequently Asked Questions
How do I get aphids out of a cauliflower head that's already infested?
Soaking the head in cold salted water for 15-20 minutes before rinsing helps dislodge aphids hiding in the florets, though a heavily infested head may never come completely clean. Preventing the infestation in the first place, which is what this pairing is aimed at, is far easier than fixing it after the fact.