Rue

Rue has a genuine reputation as a pest deterrent, and some of it holds up. Planted near roses, it's said to discourage Japanese beetles and aphids — the volatile oils in the foliage are off-putting to a range of insects. The same principle applies near brassicas like cabbage and broccoli: placing rue in or around those beds breaks up the solid monoculture blocks that let crop-specific pests spread unopposed. NC State Extension's IPM guidance specifically recommends mixing plant families to slow that kind of buildup, and rue's strong scent adds another layer of disruption. Carrots, onions, and garlic are straightforward neighbors — no meaningful pest overlap, no root competition worth worrying about at 18–24 inch spacing.

Marigolds work well in the same area for related reasons. Two pungent plants together tend to confuse generalist pests more than either one alone, and marigolds stay low enough that they won't shade out rue's preferred full sun. Fig trees are a traditional pairing with a long paper trail — rue is historically planted at the base of figs to deter fig-boring insects — and since figs grow large and rue tops out at 2–3 feet, there's no real competition for light or space.

The companions to avoid are pretty definitive. Basil, sage, and mint all appear to suffer near rue, likely from allelopathic compounds it releases through root exudates and decomposing leaf litter. Rue also produces furanocoumarins — the same compounds that make it photosensitizing on skin contact — so place it somewhere you won't be brushing past it repeatedly while tending close-in crops.