Brussels Sprouts and Nasturtium
Beneficial Pair — Good Match
The trap-cropping research behind nasturmtium's dual role isn't specific to one brassica species, so it applies to brussels sprouts on the same basis it does to cabbage or broccoli.
Mechanism: Trap Cropping
Brussels sprouts share the same aphid and cabbage white butterfly pressure documented in depth on this site's cabbage-and-nasturtium page, and nasturtium's pull on both pests works no differently here simply because the brassica in question grows sprouts along a stalk instead of a single head.
Brussels sprouts' unusual growth habit - a single tall stalk rather than a broad bushy plant - changes how nasturtium fits into this pairing more than the underlying pest mechanism does.
A Growth Habit That Actually Suits This Trap Crop
Unlike cabbage or broccoli's wider canopy, a brussels sprouts stalk leaves meaningful open ground at its base for much of the season as sprouts develop upward along the stem. That open space is a natural fit for nasturtium's own sprawling habit, letting it occupy ground that would otherwise sit bare rather than competing for a limited bed footprint.
The long growing season does mean more time for the trap crop to need attention, though - check nasturtium regularly across the full months brussels sprouts are in the ground, not just early on.
Spacing
Brussels sprouts grow as a single tall stalk with sprouts forming along its length, leaving the ground at its base relatively open for much of the season - nasturtium can occupy that space directly rather than needing a wide separate border.
Watch For
Because brussels sprouts stay in the ground for months, monitor the nasturtium planting at the same cadence you would for a long-season crop - an unchecked trap crop left in place for that long has more time to become overwhelmed than one paired with a faster-maturing brassica.
Frequently Asked Questions
Does the trap-crop protection start as soon as I put both plants in, or does the nasturtium need time to be useful?
It needs some real size first - a freshly sown or just-transplanted nasturtium seedling doesn't offer much of a pull yet, so early in brussels sprouts' long season the crop is effectively unprotected regardless of what's planted nearby. Starting nasturtium from a nursery transplant rather than seed closes that early gap faster if you want the trap-crop effect working sooner rather than waiting out a slow germination period.
Brussels sprouts stay in the ground into winter in many zones - does the nasturtium need to be replanted partway through to keep working?
No, but its usefulness has a natural end point - nasturtium is frost-tender and will be killed by the first real freeze, while brussels sprouts, a genuinely cold-hardy crop, keep going well past that point in many zones. Once frost takes the nasturtium, treat the trap-crop benefit as finished for the season rather than replanting it; winter cold suppresses aphid activity directly from that point on anyway.