Onion
Allium cepa
AmaryllidaceaeCompanion plants for onions
The best companion plants for onions are cabbage, peppers, tomatoes, cucumbers and dill. Peas and asparagus are best kept away. Of the 20 plants we have data on, 11 are good neighbours, 2 are bad ones and 5 are contested. 12 of these verdicts rest on field trials or research papers; the rest come from traditional companion-planting charts.
- 11 good
- 2 to avoid
- 5 contested
- 12 tested in trials or papers
Neighbours of onions at a glance
Inner rings are backed by trials or papers, outer rings by charts only. Pick a plant to see its sources.
The interactive map needs JavaScript. Every plant on it is listed below with its evidence.
Good companion plants for onions
Biggest harvest gain first, then the plants tested without a yield count. Each row links to the full evidence for the pair.
| Plant | What trials found with onions | Tested by | Garden charts |
|---|---|---|---|
 Beet |
64% more harvest from the same space | Field trial1 study | Recommend |
 Pepper |
20% more harvest from the same space | Field trial6 studies | Recommend |
 Cabbage |
Fewer pests and draws in pest-eating insects8% more harvest from the same space | Field trial8 studies | Recommend |
 Tomato |
Better soil and nutrient uptake and bigger combined harvestMixed results on soil and nutrients | Field trial7 studies | Not listed |
 Cucumber |
Helpful plant chemistry and bigger combined harvest | Field trial3 studies | Recommend |
 Dill |
Draws in pest-eating insects | Field trial1 study | Recommend |
 Cauliflower |
Bigger combined harvest | Field trial1 study | Not listed |
Harvest from the same space compares a bed with both crops against the same area split into single-crop beds, counting the harvest of both crops (the land equivalent ratio in yield trials).
Recommended by garden charts, not tested yet
We found no trial or paper on these pairs with onions. They may still work; nobody has measured it.
What not to plant with onions
| Plant | What trials found with onions | Tested by | Garden charts |
|---|---|---|---|
 Pea |
No trial found | Not tested | Advise against |
| Asparagus | No trial found | Not tested | Advise against |
Relatives that share pests and diseases
| Plant | What trials found with onions | Tested by | Garden charts |
|---|---|---|---|
 Garlic |
No trial foundSame family (Amaryllidaceae): shares pests and diseases | Not tested | Not listed |
 Chives |
No trial foundSame family (Amaryllidaceae): shares pests and diseases | Not tested | Not listed |
Contested pairings
The sources disagree, or the charts say one thing and the trials another. Open a pair before you plant it.
| Plant | What trials found with onions | Tested by | Garden charts |
|---|---|---|---|
 Bean |
43% more harvest from the same space | Field trial1 study | Advise against |
 Carrot |
Fewer pestsMixed results on pests | Field trial2 studies | Recommend |
 Potato |
Fewer pestsMixed results on pests | Field trial2 studies | Recommend |
 Fava bean |
Mixed results on harvest | Field trial1 study | Not listed |
 Melon |
Mixed results on harvest | Field trial1 study | Not listed |
Sources
40 sources behind the verdicts on this page. 13 chart entries cite no source and are marked as tradition only.
Show all 40 sources
Crop Rotation in the Vegetable Garden (Steil · 2025 · Iowa State University Extension and Outreach, Yard and Garden)
Intercropping with potato-onion alters arbuscular mycorrhizal fungi spore-associated bacterial communities of tomato rhizosphere. (Zhou L · 2025 · Frontiers in microbiology)
Mechanisms of root exudates and soil microbial responses to nitrogen reduction and companion cropping for tomato yield increase and quality improvement. (Liu D · 2025 · Frontiers in plant science)
Potato-onion intercropping enhances tomato yield and quality and modifies soil microbial diversity. (He X · 2025 · Scientific reports)
Root separation modulates AMF diversity and composition in tomato-potato onion intercropping systems. (Ibrahim M · 2025 · Frontiers in microbiology)
Management of Flea Beetles Using Ecological Engineering in Vegetable Agroecosystem of Kashmir (Maqsood S · 2024 · Research Square)
Tillering onion AcPAL and AcALL genes regulate trans‐cinnamic acid and allicin accumulation to improve cucumber environmental adaptability and growth (Fu Y · 2024 · Physiologia Plantarum.)
Experimental dataset of the impact assessment of vegetable intercropping on agroeconomic performances, pests and beneficials, and soil resources. (Perrin B · 2023 · Data in brief)
The Best Onion Companion Plants (2022 · Growfully)
Common mycorrhizal networks benefit to the asymmetric interspecific facilitation via K exchange in an agricultural intercropping system (Gao D · 2021 · Biology and fertility of soils)
Biochar and Intercropping With Potato-Onion Enhanced the Growth and Yield Advantages of Tomato by Regulating the Soil Properties, Nutrient Uptake, and Soil Microbial Community. (He X · 2021 · Frontiers in microbiology)
Disturbance and competition drive diversity effects in cabbage-aphid-onion systems with intra-specific genetic variation. (Guilbaud CSE · 2020 · Bulletin of entomological research)
Intercropping with Potato-Onion Enhanced the Soil Microbial Diversity of Tomato. (Li N · 2020 · Microorganisms)
[Effects of three intercropping species on growth, nutrition absorption, and fruit quality of oriental melon]. (Ma YJ · 2020 · Ying yong sheng tai xue bao = The journal of applied ecology)
Agronomic performance and biological efficiency of kale intercropped with spice species (Alves De Araujo Hendges · 2019)
Trap Crops in Onion to Reduce Onion Thrips1 and Iris Yellow Spot Virus (Buckland KR · 2017 · Southwestern Entomologist)
Evaluation of vegetable–faba bean (Vicia faba L.) intercropping under Latvian agro‐ecological conditions (Lepse L · 2017 · Journal of the science of food and agriculture.)
Effect of bokashi and vermicompost leachate on yield and quality of pepper (Capsicum annuum) and onion (Allium cepa) under monoculture and intercropping cultures (Álvarez-Solís · 2016)
Maximizing Productivity by Intercropping Onion on Sugar Beet (Motagally · 2014)
Volatile exchange between undamaged plants - a new mechanism affecting insect orientation in intercropping. (Ninkovic V · 2013 · PloS one)
Effect of intercropping chili (Capsicum annuum L.) with onion (Allium cepa L.) in sandy regosol (Brintha · 2012)
Agronomic Performance of Collards under Two Intercrops and Varying Nitrogen Application Levels as Assessed Using Land Equivalent Ratios (Mutiga · 2011)
[Effects of intercropping Chinese onion cultivars of different allelopathic potential on cucumber growth and soil micro-environment]. (Yang Y · 2011 · Ying yong sheng tai xue bao = The journal of applied ecology)
Intercropping for field production of peppers (Kahn · 2010 · HortTechnology)
Effect of garlic and onion extracts or their intercropping on suppressing damping-off and powdery mildew diseases and growth characteristics of cucumber (Morsy · 2009 · Egyptian Journal of Phytopathology)
Effect of Intercropping Collard with Beans or Onions on Aphid Populations and Yields of Collard Under High Altitude Conditions in Kenya (Saidi · 2008)
Evaluation of the Yield Components and Yield of Onion (Allium cepa L.)-Pepper (Capsicum annuum L.) Intercrop in the Sudan Savanna (Kabura · 2008)
[Effects of rotation and intercropping on bacterial communities in rhizosphere soil of cucumber]. (Wu FZ · 2008 · Ying yong sheng tai xue bao = The journal of applied ecology)
Yield and economics of chilli based intercropping system (Suresha · 2007)
Increasing Productivity with Intercropping Systems in Cabbage Production (Guvenc I · 2006 · Journal of sustainable agriculture)
Intercropping based on cauliflower: More productive, profitable and highly sustainable (Yildirim · 2005)
Productivity, Quality and Profit of Sole or Intercropped Green Beau (Phaseolus vulgaris L.) (Abou-Hussein Sd · 2005)
Economic Returns and Yield of Chilli as Intercropped with Varying Onion Population (Tarafder · 2003)
Effect of intercropping on the population density of pests in some vegetables (Mateeva · 2002 · Acta Horticulturae)
Aspects of biologically based pest management in commercial pepper production (Frantz · 1997 · Proceedings of the Florida State Horticultural Society)
The influence of intercropping with Allium on some insect populations in potato (Solanum tuberosum) (Potts · 1991 · [[Annals of Applied Biology]])
Effect of mixed cropping on some insect pests of carrots and onions (Uvah III · 1984 · Entomologia Experimentalis et Applicata.)
Companion Plants (Alabama Cooperative Extension System)
Companion planting: A method for sustainable pest control (Riesselman · Iowa State University)
What grows well with your onions?
Share what worked next to your onions and what did not, or ask other growers a question. Reader notes are not checked by us and do not change the verdicts on this page.