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Onions growing alongside carrots in a raised bed—an example of companion planting to help deter pests and improve crop health.
What to Plant with Onions for Better Growth, Fewer Pests, and Healthier Bulbs
Onions are powerful companion plants that help repel pests and support healthier garden growth. But they also perform best when paired with the right neighbors. Here’s what to plant with onions to improve bulb size, reduce weeds, and make the most of your garden space.
Key Takeaways
- Companion planting with onions helps repel pests like carrot flies, aphids, and cabbage worms thanks to their strong scent.
- Onions grow well with crops like carrots, beets, cabbage, lettuce, and strawberries, improving plant health and reducing pest pressure.
- Many onion companions also help suppress weeds, improve soil structure, and make efficient use of garden space.
I’ve been using onions in my garden for years and have found they’re some of the most reliable companion plants for a wide range of vegetables, herbs, and flowers.
Why Companion Planting Works for Onions
Onions and other alliums release a strong, sulfur-like scent that helps deter pests like carrot flies, cabbage loopers, and Japanese beetles. Planting onions around the edges of garden beds may also discourage larger pests, such as deer and rabbits.
While onions are known for protecting nearby plants, they also grow best with the right companions. The best onion companion plants help suppress weeds, improve soil structure, and support the development of larger, healthier bulbs.
How Companion Planting Helps Prevent Onion Pests
Companion planting works by disrupting pest behavior and attracting beneficial insects. Strong-smelling plants like onions can mask the scent of nearby crops, making it harder for pests to locate them, while flowers and herbs bring in predators that help keep pest populations in check.
Companion Plants for Onions
Onions love sun, rich soil, and regular watering, so any companion plant you choose to grow with them should have similar care needs. Most gardeners keep onions in veggie beds, but they can also benefit ornamental plants. If you want to enjoy all the benefits that companion planting with onions brings, here are some of the best companion plants to grow with onions and why these plant pairings work!
Some of the best companion plants for onions include the following:
Brassicas
Cabbage loopers are the biggest nemesis for the Brassica plants in my garden, but they’ve been much less problematic since I’ve started interplanting Brassicas with onions.
I’ve tried this with kale, Brussels sprouts, cauliflower, collard greens, and broccoli, and definitely see fewer loopers on my veggies. I still use row covers with brassicas, though, and I’ll sometimes spot-treat plants with BT thuricide if a few cabbage loopers sneak in.
Nightshades
I’ve lost more than a few bell peppers to deer over the years, but I haven’t lost any since I began growing bell peppers with onions. Onions can also help repel a variety of pests from other nightshade plants, including tomatoes, eggplants, and tomatillos.
Plus, if you grow these plants together, you’ll conveniently have most of the ingredients you need for homemade salsa.
Savory
Summer and winter savory don’t just pair well with onions in the kitchen. These herbs also grow well with onions in the garden and can actually enhance the growth and flavor of neighboring onion plants.
On top of that, savory and onions both repel the pests that are attracted to each other!
Roses
Growing onions with roses can seem a little odd at first, but onions and other alliums do wonders for keeping Japanese beetles and other rose pests in check.
If you want to try this hack, plant onions in a ring around your roses or grow them along the borders of your rose beds. Just keep in mind that you may not want to harvest onions for eating if you apply fungicides and other chemical treatments to your rose plants.
Strawberries
Strawberries are one of the most popular fruiting plants for home growing, but they are prone to pests. Keeping onions near your strawberry plants should reduce pest activity and help you harvest blemish-free berries.
In return, sprawling strawberries will serve as a living mulch, keeping weeds from encroaching on your onions.
More Plants That Grow Well with Onions
Beets
Beets can be plagued by deer, rabbits, and flea beetles, but growing beets and onions together should help protect beet greens from these garden marauders. Not to mention, beets and onions have similar care needs, and growing them together will simplify garden care.
Dill
Dill and onions are both essential ingredients for homemade pickles, and growing these plants together reduces the ingredients you’ll need to buy for home canning.
If you allow dill plants to flower, they’ll also attract beneficial insects to your garden that feed on onion pests!
Chamomile
Chamomile is often grown as an ornamental or as an herb for homemade teas. But this daisy-like flower makes an exceptional companion plant for many veggies and can enhance the flavor and growth of onions planted nearby.
Chamomile flowers are also highly attractive to beneficial bugs like hoverflies that feed on insect pests.
Carrots and Parsnips
Similar to beets, carrots and parsnips are root veggies that have similar growing requirements to onions. But that’s not the only reason to keep these plants together.
The strong scent of onions helps repel carrot flies that feed on carrot roots, while harvesting carrots aerates the soil and can make it easier for onion bulbs to fill out—just as long as you don’t disturb your onions when harvesting! Want to learn more? See our companion plants for carrots guide.
Marigolds
Although onions are relatively hardy crops, they can sometimes be targeted by pests like nematodes. Luckily for home gardeners, marigolds help to naturally reduce nematode pests and can protect onion crops from significant damage.
For best results, plant marigolds in your garden at least 2 months before growing onions, or grow marigolds in the fall and till them into the soil before planting onion sets in spring.
Looking to plan your full garden layout? Browse our Companion Planting Chart to see the best plant pairings at a glance.
What Not to Grow with Onions
Onions grow well with many plants, but there are a few exceptions. Avoid planting onions near the following crops to prevent reduced growth or competition for nutrients.
| Plant | Why Avoid? |
|---|---|
| Beans and Peas (Legumes) | Onions can interfere with nitrogen-fixing bacteria in legumes, which may reduce growth for both plants. |
| Sage | Sage prefers drier soil conditions and can stunt onion growth when planted too closely. |
| Asparagus | Both onions and asparagus are heavy feeders and may compete for nutrients. Harvesting onions can also disturb asparagus crowns. |
FAQ
What should you not plant near onions?
Onions don’t grow well with beans and peas, nor do they grow well with some Mediterranean herbs like sage, which prefer dry soil.
What is a good companion plant for onions?
Onions are great companion plants for many crops, including strawberries, roses, brassicas, and carrots.
What do onions repel?
Thanks to their strong, sulfur-like scent, onions help repel pests such as deer, rabbits, Japanese beetles, flea beetles, carrot flies, and cabbage loopers.
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