companion plants for onions

10 Best Companion Plants for Onions + 2 to Avoid

Plan your garden for success with this list of companion plants for onions and see a thriving garden this growing season!

What can we plant with onions? Many beginner gardeners hear about companion planting when they start growing and get confused because the information can be conflicting! Especially when it comes to plants like onions! 

And while onions and other crops in the allium family get a bad wrap, they are in fact one of the friendliest plants in the garden when it comes to companion planting! 

In this onion companion planting guide we are going to get the truth about companion planting with alliums and learn what crops are good companion plants for onions!

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Benefits of Companion Planting with Onions

As I mentioned earlier, onions make good companions to many different plants in the garden, but why are they such great friends? 

Well onions are members of the allium family (along with leeks, green onions, and garlic), which are a family of crops that are known for their strong scent. This strong scent helps to deter many common garden pests, making onions and other alliums great natural pest control for those aspiring to be organic gardeners! 

But that’s not all, onions also have a shallow root system which allows them to be planted closely with other crops without competing for nutrients. This makes them a good companion plant in small gardens or square foot gardens where space may be limited.

If you happen to allow your onions to flower, these showy bulbs can be a magnet for beneficial insects and pollinators early in the season.

Common Pests and Diseases of Onions

One of the reasons that onion plants are such great companions is the fact that they aren’t susceptible to many diseases or pests in the garden, but they aren’t invincible! There are some pests that can wreak havoc if left unchecked even for hearty onions!

Onion Maggots or Onion Flies can quickly devastate an onion crop, causing stunted growth and even death. These pests lay eggs at the base of the plant which hatch into maggots that feed on the roots and bulbs.

Thrips are another common pest that can plague onions, causing yellowing leaves and distorted growth.

Leafminers are identified by the trails their larvae leave on onion leaves as they feed and can cause significant damage to the plant if left untreated.

Rust is a fungal disease that can affect onions and other alliums, causing orange or yellow spots on the leaves.

These pests are diseases are going to be more common in market and larger scale farming where the sheer number of plants make it easier for these pests to reproduce. But as a home gardener, we have the advantage of being able to closely monitor our plants and catch any issues early on.

Best Companion Plants for Onions

Now that we’ve covered the benefits of companion planting with onions and some common pests and diseases, let’s dive into which crops make good companions for onions. 

As a reminder, I will share my quick formula for creating your own companion planting planning in your raised garden bed or containers! Remember, there are three key elements, a main crop, a flower, and an herb! For this gardening method, onions and most alliums are going to be used in the formula as an herb!

But the first two companions on our list can be used as the flower and herb if you are following the formula and considering onions a main crop. 

Chamomile

Chamomile is a flowering herb plant that can be planted as a companion to onions! In the garden, chamomile’s strong odor may rival that of onions and repel common onion pests. (Chamomile does attract thrips which could be used as a trap crop to keep them from your onion plants. Additionally, it is thought that growing chamomile near your onions can improve the flavor on onions. 

Summer Savory

Summer Savory is another great companion plant for onions although it is not often planted in the garden! It grows similar to and has a flavor like marjoram, oregano and thyme! It is thought to sweeten the flavor on onions, and counts as the herb to plant with onions in the companion planting formula.  

Brassicas

Brassica plants are members of the cabbage family such as brussels sprouts, broccoli, and collard greens and are some of the most pest ravaged crops in the garden! Cabbage moths, cabbage worms, and cabbage loopers can demolish a brassica crop in days, so beware of those really cute white butterflies fluttering through the garden! 

Interplanting onions with your brassica plants can significantly decrease the scent of these crops and minimize pest damage! (I have also found using insect netting can make a huge difference!)

Lettuce

Lettuce grows great alongside onions because the onions’ strong scent can ward off pests that commonly plague lettuce plants. In addition, lettuce has a shallow root system in different layers of soil than onions so it doesn’t compete for nutrients.

Tomatoes

Onions make great companions for tomato plants because they deter pests like aphids and thrips that can harm tomatoes. Additionally, onions have a shallow roots which means they won’t compete for nutrients with the deep rooting tomato plant.

Carrots

Onions and carrots are typically found together in many recipes, but did you know they also make great companions in the garden? Onions deter the carrot fly from laying eggs near  your carrot plants, which can damage or kill the plant.

Strawberries

Strawberries are another great companion for onions, not only because onions have shallow roots and don’t compete for nutrients, but also because their strong odor can repel pests like slugs and snails that commonly target strawberries.

Peppers

Pepper plants are often plagued with aphid infestations early in the growing season! The tender green leaves of maturing peppers often attract these fast growing pests! Planting onions with your pepper plants is a great way use the companion planting method to deter aphids and other pests that can harm peppers. 

Celery

Planting onions with your celery plants can be a great idea because of the antifungal properties of onions which can help prevent diseases that affect celery plants. 

Beets

Root crops like beets make excellent companions for onions in the garden. Onions have a natural ability to repel aphids, pesky insects that can hinder beets’ root development and growth. By planting these two together, you not only promote healthy growth but also create a natural defense system for your garden.

Also Read: How to Grow Onion Sets + Simple Tips for Larger Bulb Onions in 2024

Companion Planting Precautions

Now that we know what we can plant with onions, lets take a brief moment to discuss the crops that you should avoid planting near onions!

Legumes

Crops in the legume family like pole beans, bush beans, peas, and peanuts should not be planted near onions because onions release chemicals that can kill needed soil bacteria. This chemical incompatibility ultimately hinders the growth of legumes! It’s a good idea to consider crop rotations that do not allow beans to follow onions without soil amendments. 

Other Allium family members

While some may recommend planting onions with other members of the allium family, I want to add caution to this pairing, especially when you live in an area that has high prevalence of diseases that affect onions plants. 

Additional Companion Planting Tips

Successful companion planting doesn’t have to be hard especially when you understand why you are doing it, but I do understand that as a beginner it can be quite confusing! That is why we created the Companion Planting series on our Podcast: Garden Things with Friends! 

In this series, instead of simply learning lists of crops you can plant together, you’ll get a better understanding of why certain plants work well together and others do not in this gardening technique. You’ll also learn about other factors that can affect companion planting, such as soil quality and garden layout. You can check out each of the videos in this three part series below:

Ep. 11 – What is Companion Planting + FREE Printable Companion Planting Chart

Ep. 12 – 12 Best Herbs for Companion Planting in the Vegetable Garden

Ep 13 – 10 Best Flowers for Companion Planting with Your Vegetables

Don’t be afraid to experiment with companion planting in your garden. It’s a fascinating way to enhance plant growth and overall garden health. Remember, research is key! By studying which plants complement each other, you can create a harmonious garden ecosystem. With the right information and a bit of trial and error, you’ll discover the perfect companions for your onion plants and all the main crops in your garden. Happy planting!

Companion plants for onions

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