Companion Plants for Onion
Onion thrives alongside Carrot, Beet, Lettuce, and more. Here's the complete guide to what to plant nearby — and what to keep at a distance.
✅ Best Companions for Onion
These plants improve each other's growth, deter pests, or attract pollinators when planted nearby.
Uses underground space while Onion occupies the canopy above — minimal resource competition, maximum bed productivity.
View Carrot's companions →Uses underground space while Onion occupies the canopy above — minimal resource competition, maximum bed productivity.
View Beet's companions →Compatible neighbors that share space and resources efficiently without competing for the same nutrients.
Compatible neighbors that share space and resources efficiently without competing for the same nutrients.
View Tomato's companions →Compatible neighbors that share space and resources efficiently without competing for the same nutrients.
⚠️ What Not to Plant Near Onion
These combinations can stunt growth, attract pests, or compete heavily for the same nutrients.
Can inhibit growth or share pests and diseases — keep a full bed-width apart.
Can inhibit growth or share pests and diseases — keep a full bed-width apart.
View Pea's companions →Can inhibit growth or share pests and diseases — keep a full bed-width apart.
View Asparagus's companions →🤝 Plants That Benefit from Onion
These plants list Onion as a beneficial neighbor — so the relationship goes both ways.
📐 How to Plant Onion with Companions
Start with spacing
Plant Onion at its recommended spacing (4" apart) first. Don't crowd it — healthy air circulation reduces disease.
Add herbs at the edges
Aromatic companions like Carrot work well tucked 6–12" around the perimeter of the Onion planting.
Watch for height conflicts
Place taller companions (sunflowers, corn) on the north side of the bed so they don't shade Onion. Low-growing herbs and flowers can go anywhere in the bed.
Keep incompatible plants a bed away
Bean and Pea should be planted in a separate bed — ideally 3+ feet away — to prevent root exudate and pest crossover.
Plan a companion bed for Onion
Use the interactive planner to drag Onion and its companions onto a canvas, see spacing footprints, and catch conflicts before you plant.
Frequently Asked Questions
What are the best companion plants for Onion?
The best companion plants for Onion are Carrot, Beet, Lettuce, Tomato, Brassicas. These plants either deter pests, attract beneficial insects, or improve growing conditions when planted nearby.
What should you not plant near Onion?
Avoid planting Onion near Bean, Pea, Asparagus. These plants can compete for nutrients, inhibit growth, or attract shared pests.
Can you plant Onion in a raised bed with companions?
Yes — raised beds are ideal for companion planting because you control exact spacing and layout. Use the square-foot method to place Onion alongside its best companions within the same bed.
What plants benefit from being near Onion?
Strawberry, Chamomile, Dill, Beet all benefit from proximity to Onion.
How far apart should I plant Onion and its companions?
Give Onion its full 4" spacing. Plant compact companions like herbs 6–12" away at the bed edge, and taller companions (sunflowers, corn) where they won't shade the main crop. In raised beds, use the square-foot grid method for precise spacing.
Does companion planting actually work for Onion?
Research supports several companion planting mechanisms: aromatic herbs like basil can reduce aphid populations near tomatoes; marigolds release thiophene compounds that deter nematodes; and flowers attract parasitic wasps that control caterpillars. Results vary by garden, but most gardeners see measurable pest reduction within one season.
Want the full Onion growing guide?
Spacing, planting dates by ZIP code, seed saving tips, and more.