Companion Plant Guide
Carrot
Pest-confusion pairing — each hides the other from its fly.
Vegetable · Allium family
Onion companion plants
Allium cepa
What to plant beside onion, what to keep apart, and how to grow it — sun, spacing, soil and the pairings used in this guide.
Photo: Lars Blankers on Unsplash
Overview
Growing onion beside the right neighbour
Onion (Allium cepa) is a vegetable in the Allium family. Bulb crop that stores well and repels many pests.
Onions ask little of the soil, so they slot neatly into gaps between hungrier crops.
Give plants 4–6 in in full sun. Aim for well-draining, fertile soil. In most gardens the crop sits in USDA zones 3-10 and is ready in about 100-120 days.
Grows well with
What to plant with onion
The strongest companions for onion in this guide are Carrot, Lettuce, Pepper, and Beet. Each pairing below is a reason to share a bed — pest masking, roots that do not compete, or insects that hunt the pests onion attracts.
Lettuce
Pest deterrent for lettuce.
Pepper
Pest deterrent and space efficient.
Beet
Different root depths; onions help deter beet pests.
Keep apart
What not to plant with onion
Keep onion away from Bean. These neighbours compete for the same food, release chemicals that stunt growth, or otherwise hold the crop back.
Bean
Alliums stunt beans and slow nitrogen fixation.
In the bed
How to grow onion
| Sun | Full sun |
|---|---|
| Spacing | 4–6 in |
| Soil | Well-draining, fertile soil |
| Hardiness | Zones 3-10 |
| Days to maturity | 100-120 |
These notes sit beside the companion lists — they are how onion actually occupies the bed, not a substitute for local climate.
- Plant sets in spring or fall for best results
- Thin to proper spacing for good bulb formation
- Stop watering when tops fall over
- Cure bulbs in warm, dry place before storage
Questions
Onion companion planting FAQ
What can I plant next to onion?
Plant Carrot, Lettuce, Pepper, and Beet beside onion. Carrot: Pest-confusion pairing — each hides the other from its fly. Lettuce: Pest deterrent for lettuce. Pepper: Pest deterrent and space efficient. Beet: Different root depths; onions help deter beet pests.
What should I not plant with onion?
Keep onion apart from Bean. Bean: Alliums stunt beans and slow nitrogen fixation.
How much sun does onion need?
Onion wants full sun. Space plants 4–6 in apart in well-draining, fertile soil.
How long does onion take to mature?
Most onion crops in this guide mature in 100-120 days, in hardiness zones 3-10.
Compare every pairing at a glance
Open the guide, pick onion, and see what thrives alongside it — and what quietly holds it back.
Open the pairing guide