Broccoli and Nasturtium
Beneficial Pair — Good Match
The underlying research on nasturtium's dual role against aphids and cabbage white butterfly is the same body of work discussed for cabbage - it isn't specific to one brassica, so it transfers to broccoli without needing separate confirmation.
Mechanism: Trap Cropping
Nasturtium's documented preference for aphids and cabbage white egg-laying, covered in more depth on this site's cabbage-and-nasturtium page, applies the same way to broccoli, a close relative sharing the same key pests.
Broccoli shares the same documented pest profile as cabbage, so nasturtium's trap-cropping role transfers directly - the real difference here is how long broccoli keeps producing after its main harvest.
A Longer Window to Protect Than a Single-Harvest Crop
Once the central head is cut, a healthy broccoli plant continues producing smaller side shoots for weeks, sometimes over a month, extending the period during which cabbage white butterflies and aphids remain a threat. A nasturtium border planted and then neglected once the first big harvest is in risks leaving that longer side-shoot window unprotected.
This is worth planning for specifically, since it's easy to assume the job is done once the main broccoli head has been cut and the pressure of the first harvest is behind you - the plant, and the pest risk, are both still active.
Spacing
Border the broccoli bed with nasturtium the same way described for cabbage, 12-18 inches out, positioned to intercept pests approaching from any direction.
Watch For
Broccoli's harvest doesn't end when the central head is cut - side shoots keep forming for weeks afterward, so the nasturtium border needs to stay intact and monitored well past that first harvest, not just through the main head's development.
Frequently Asked Questions
Does the nasturtium border itself keep blooming long enough to cover broccoli's whole side-shoot period, or does it need refreshing partway through?
A healthy nasturtium planting typically blooms continuously for months once established, so it doesn't need replanting mid-season the way some shorter-lived companion flowers do - the main risk is heat stress in a hot summer stretch, which can slow nasturtium flowering right when broccoli's side shoots still need the coverage.
If I'm growing broccoli alongside other brassicas like cabbage in the same bed, does one nasturtium border protect all of them, or does the benefit get diluted?
One well-placed border can work for a mixed brassica bed, since the trap-cropping effect isn't tied to a single plant's proximity so much as nasturtium's overall presence drawing pest attention away from the bed generally - but a border sized for one crop's footprint won't necessarily reach a bed that's grown considerably larger by adding more brassicas. Scale the border's length to the bed's actual perimeter rather than assuming a border planned for broccoli alone still covers cabbage added later.