6 Onion Companion Plants & 5 Bad Neighbours to Avoid

Steve Yoder

I'm Steve, a 30-something urban gardener fascinated by companion planting research. Growing up surrounded by greenery sparked my passion for gardening early on. I enjoy transforming my small backyard, experimenting with companion planting techniques and eco-friendly practices. Sustainability matters—I advocate for native plants and composting.

When planting onions, it’s important to understand the benefits and limitations of onion companion plants. You can plant onions in almost any climate, but they grow best when planted in groups rather than alone. Planting them with companion plants adds nutrients to the soil. This improves growth by deterring pests from attacking your plants. Let’s have a look at 6 onion companion plants and 5 plants to avoid as neighbours.

Onion Companion Planting

Onion companion planting is a way to grow onions in a way that benefits other plants. Companion planting is used to create an environment where your desired plants thrive. You can use companion planting with many different types of vegetables.

Onion-growing tips:

Soil should be well-drained, rich in organic matter, and not too acidic (pH 6-6.8).
Use a balanced fertilizer at planting time and again when the tops begin to show.
Thin to 6 inches apart for scallions or bunching onions; 12 inches apart for storage onions.

Benefits of Onion Companion Planting

The benefits of companion planting are many. First, it can help deter pests and weeds (which can lead to healthier onions). Second, it attracts beneficial insects that help keep those pesky pests at bay. Third, your soil structure will improve by the presence of companion plants. Soil absorbs water and nutrients easier when it isn’t compacted by tall crops like corn or soybeans. Finally, if you’re interested in growing your food organically with as little chemical intervention as possible, companion planting will go a long way toward reducing the need for pesticides!

Onions aren’t just great for you—they also make wonderful companions for other garden plants. Onions benefit from being planted with many different types of flowers and vegetables. In this was, they take up space in your garden and encourage beneficial insects. For example ladybugs will come to check out what kind of goodies they might find there!

Onion Companion Plants

Although onions are a self-sufficient plant, they do benefit from the presence of certain companion plants. Onion companion plants help deter pests and keep the soil healthy and enriched. This makes it easier for you to grow your onions. There are many types of onion companion plants that you can experiment with. Yet, here are some tried-and-true favorites:

Garlic: This member of the lily family is a great companion for all types of onions. It deters pests such as aphids and thrips, while also encouraging beneficial insects to visit your garden. It’s also good at repelling rabbits and other critters who might want to taste your delicious crop!
Carrots: Carrots and onions make an excellent pair! They help protect against root disease in onions and repel nematodes from damaging them further. They also improve soil structure by adding organic matter into the ground as they grow. This means better drainage for both crops when planted side-by-side!
Radishes: Radishes aren’t just tasty additions to sandwiches or salads. They’re also great companions for growing with any type of bulbous plants like garlic or leeks. That’s beccause their roots combine well together in certain soils. Especially sandy ones which tend not to keep water very well!
Chives: These are great companions for onions because they attract hoverflies. They will prey on aphids in your garden!
Mints: Mints like spearmint or apple mint act as an aromatic foil to the pungent fumes of onions. These plants release an aroma that masks them. This is especially helpful if you have neighbors close by who might not appreciate being woken up at night by strong onion smells wafting through their windows! You can also plant mint near nasturtiums or sage for a double-whammy combo!
Marigold: Marigold is an effective plant with active volatiles that attracts natural enemies. This leads to lower pest population.^1,² It is an important plant that maintains a high natural enemy biodiversity. ^3,^4,⁵ Marigold as onion companion plant provides an eco-friendly strategy to reduce pest population. ^6,^7,⁸

What not to Plant with Onions

You should avoid planting onions with:

Vegetables like tomatoes, potatoes, or beans are all members of the nightshade family. They may have an antagonistic effect on each other. This is a good general rule to follow when planting companion crops. Be sure to check the compatibility between any two crops before you start digging holes!

Lettuce and onions also don’t like each other much. They’re both susceptible to diseases caused by fungi so they’re best kept apart.

Onions don’t interact well with strawberries either (or any berry plants). They can also harbor some of the same diseases as lettuce.

References

Bhattacharyya, M. (2017). The push-pull strategy: A new approach to the eco-friendly method of pest management in agriculture. Journal of Entomology and Zoology studies, 5(3), 604-607.
Khan, Z., Midega, C. A., Hooper, A., & Pickett, J. (2016). Push-pull: chemical ecology-based integrated pest management technology. Journal of chemical ecology, 42(7), 689-697.
Silveira, L. C. P., Berti Filho, E., Pierre, L. S. R., Peres, F. S. C., & Louzada, J. N. C. (2009). Marigold (Tagetes erecta L.) as an attractive crop to natural enemies in onion fields. Scientia agricola, 66, 780-787.
Silveira, L. C. P., Bueno, V. H. P., & Mendes, S. M. (2003). Record of two species of Orius Wolff (Hemiptera, Anthocoridae) in Brazil. Revista Brasileira de Entomologia, 47, 303-306.
Silveira, L. C. P., Bueno, V. P., & Van Lenteren, J. C. (2004). Orius insidiosus as biological control agent of thrips in greenhouse chrysanthemums in the tropics. Bulletin of insectology, 57(2), 103-109.
Martowo, B., & Rohana, D. (1987). The effect of intercropping of pepper (Capsicum annum L.) with some vegetable crops on pepper yield and disease incidence caused by Meloidogyne spp. Buletin Penelitian Hortikultura, 15, 55-59.
Abid, M., & Maqbool, M. A. (1990). Effects of inter-cropping of Tagetes erecta on root-knot disease and growth of tomato. International Nematology Network Newsletter, 7(3), 41-42.
Abid, M., & Maqbool, M. A. (1990). Effects of inter-cropping of Tagetes erecta on root-knot disease and growth of tomato. International Nematology Network Newsletter, 7(3), 41-42.