About Onion
Onion releases sulphur compounds that deter many soil and flying pests — a classic companion for carrots and leafy greens. Alliums and legumes are famously poor neighbours in the same row.
Garlic rust is common in humid areas — rotate beds and avoid overcrowding.
Good companions
Plants that pair well with Onion — tap for their guides. Cited sources appear where research is linked in the matrix.
Onion scent may confuse carrot fly; carrots may deter onion fly — a classic paired row in UK/NZ guides.
Tomato Pest confusionOnions and alliums are often interplanted with tomatoes — scent may confuse some soil pests though evidence is mixed.
Lettuce Spatial pairingLettuce fills shallow gaps between onion rows — efficient use of bed space in succession plantings.
Cabbage Pest confusionOnions interplanted with brassicas may confuse cabbage root fly and onion fly through mixed scents.
BroccoliListed as beneficial in the matrix — open the grid for full context.
Beet Spatial pairingOnions and beets interplant well — different root depths and onion scent may reduce leaf-miner pressure on beets.
Sweet PepperListed as beneficial in the matrix — open the grid for full context.
SpinachListed as beneficial in the matrix — open the grid for full context.
Swiss ChardListed as beneficial in the matrix — open the grid for full context.
MizunaListed as beneficial in the matrix — open the grid for full context.
RhubarbListed as beneficial in the matrix — open the grid for full context.
WormwoodListed as beneficial in the matrix — open the grid for full context.
+ 4 more in the matrix
Avoid planting together
Known poor neighbours — spacing apart or rotating beds reduces shared pest and disease pressure.
Alliums may inhibit legume nodulation and growth — a well-documented pairing to avoid in the same row.
Pea Growth inhibitionAlliums may reduce pea nodulation and growth — avoid planting peas and onions in the same row.
Asparagus Growth inhibitionAlliums can stunt asparagus spears — keep onions, garlic, and leeks away from established asparagus crowns.
Lentil Growth inhibitionAlliums inhibit lentil growth and nodulation — keep lentils in allium-free beds.
Bean (Pole)Listed as incompatible in the matrix — open the grid for full context.
Fava BeanListed as incompatible in the matrix — open the grid for full context.
Growing tips
- Plant garlic in autumn for mid-summer harvest in most NZ regions.
- Carrot + onion inter-rows remain a kitchen-garden standard.
- Keep alliums away from beans and peas — see incompatible list below.
Use the compatibility matrix
Filter to Onion to see green (beneficial), red (incompatible), and grey (neutral) for every pair among 162 plants. Desktop: hover cells. Mobile: tap for details.