Onion (Allium cepa) is a perennial plant member of the Amaryllidaceae family. Though they’re perennials, they are treated as annuals in the garden. When you harvest the onion bulb to eat, it won’t grow back.
Evidence suggests that onions were grown as early as 5000 BC. They originated somewhere in Asia, but the exact location is unknown. They’ve been grown in Asia and Europe for centuries and were brought to North America by Europeans.
Though onions do a good job of repelling insects, a few insects will still feed on them. There are also a variety of diseases that can impact onions. You can use onion companion plants to alleviate some of these issues.
Here we’ve compiled all of the information about onion companion planting. We’ll explain the benefits and things to consider when choosing companion plants. We’ve also compiled a list of the best and worst plants to grow alongside onions.
Benefits Of Companion Gardening With Onion
Companion gardening has a variety of benefits for onions. Onion companion plants can improve growth and onion flavor. They can also decrease pests and plant diseases.
Onions are able to naturally repel many insect pests due to their smell. However, there are still a few insect pests that feed on onions. They include bulb mites, leafminers, onion maggots, and thrips. You can use companion plants to reduce onion insect pests.
Onions can also suffer from a variety of bacterial and fungal diseases. While proper care is the best way to reduce onion diseases, companion plants can also help.
Using onion companion planting will reduce the need for applying insecticides and fungicides.
Since onions don’t use much space above ground, you can use companion plants to maximize your garden’s productivity. There are several plants that won’t impact the growth of onions but allow you to grow more in your garden. This will ensure you maximize your growing space.
Things To Consider When Companion Planting With Onion
When choosing companion plants, it’s not just about finding plants that deter pests or improve the soil. For a plant to be considered a good companion to onions, it needs to grow well with onions. That means it needs to grow well with the same soil type, pH, sunlight, and amount of water.
Both plants need to grow well under the same growing conditions. To get the full benefits from a companion plant, it should grow just as well as your onions.
Keep reading to learn which plants make great companion plants for onions and which plants should be avoided.
The Best Onion Companion Plants
Companion plants can improve the growth and taste of onions. They can also decrease pests and diseases.
Beets
Beets make great companion plants for onions because they repel thrips. Make sure you space them out correctly so they both have space to grow.
Brassicas (Broccoli, Cabbage, Cauliflower, Kale)
Brassica plants don’t provide a benefit to onions, but they don’t cause any harm either. Planting them together will allow you to grow more at once in a smaller space. Onions will help repel Brassica pests like insects and rabbits.
Chamomile
Chamomile is one of the best onion companion plants. It has natural antibacterial and antimicrobial properties. It will help reduce fungi and bacteria that can harm onions.
Chamomile also attracts pollinators and onion insect pest predators. By increasing predators, you’ll increase the number of insect pests in your garden.
This plant can also improve the flavor of your onions.
Carrot
Carrots will help deter onion flies. Onion flies are the adults of onion maggots. Planting carrots around your onions will reduce the chances of onion maggots ruining your onions.
Dill
Dill will help reduce onion insect pests. They help reduce pests by increasing insect pest predators.
Lettuce
Lettuce is another onion companion plant that doesn’t provide a direct benefit to onions. It will simply allow you to grow more vegetables in a smaller space. Onions help lettuce by repelling lettuce insect pests.
Strawberries
Strawberries also share space with onions well to maximize gardening space. Plus, onions will help repel aphids that feed on strawberries.
Summer Savory
When summer savory grows near onions, it helps make them sweeter. Some people have also noticed summer savory seems to improve the growth of onions.
Tomatoes
Feel free to plant tomatoes with your onions. They grow well in the same conditions and won’t compete with each other. Onions will also help deter aphids and Japanese beetles which feed on tomatoes.
The Worst Onion Companion Plants
Some plants can actually harm onions by stealing nutrients and impacting growth. These are the plants you should never grow near your onions.
Asparagus
Asparagus and onions will compete for the same nutrients when grown together. This will prevent either plant from maximizing its growth. They also compete for space in the soil.
Beans and Peas
Beans and peas rely on symbiotic bacteria in their roots to grow well. The bacteria also allows them to increase nitrogen in the soil.
Onions inhibit the growth of the symbiotic bacteria. Therefore, beans and peas won’t grow very well when planted with onions.
Sage
Sage and onions have different preferences when it comes to growing conditions. That makes it very difficult to grow together. It’s almost impossible to grow them together without one or the other struggling.
Here’s a table you can use to help you design your onion companion plant garden.
| Beneficial Onion Companion Plants | Benefit | Detrimental Onion Companion Plants | Detriment |
| Beets | Repels thrips | Asparagus | Compete for nutrients and space |
| Brassicas | Neutral plant, onions repel Brassica insect pests | Beans and peas | Stunted by onions, onions kill legume’s beneficial bacteria |
| Chamomile | Reduces fungi and bacteria, increases insect pest predators, increases pollinators, improves flavor | Sage | Decreased plant growth |
| Carrots | Repels onion flies | ||
| Dill | Increases onion insect pest predators | ||
| Lettuce | Neutral plant, onions repel lettuce insect pests | ||
| Strawberries | Neutral plant, onions repel strawberry insect pests | ||
| Summer Savory | Improves growth, improves flavor | ||
| Tomatoes | Neutral plant, onions repel tomato insect pests |
