In our house, onions, garlic, and chives somehow make their way into almost every one of our dishes. While these aromatics are hard for us to resist in the kitchen, we noticed that garden pests generally avoid them. This led us to our search for the best companion pairings for alliums. Here’s what I found.
The best companion plants for alliums (onions, garlic, leeks, and chives) are brassicas, nightshade, strawberries, fruit trees, and carrots. While these companions bring some benefits to the alliums, such as improved soil health, alliums offer more benefits for their companions including pest and disease resistance.
So, while these are some of the companions for alliums, what benefits do they bring exactly, and what are some other friends (and foes) to alliums? Let’s take a closer look.
Companion Planting Pro Tips (Before You Start)
Companion planting is selecting specific plants to place together for benefits such as increasing pollination or controlling pests. Sometimes these benefits are one-sided, while others are mutual.
A famous example is The Three Sisters—planting corn, beans, and squash together. The corn provides a trellis for the beans to climb, the squash provides a ground cover, and the beans fix nitrogen in the soil. Plus, all of them provide food!
Here’s how to get the most from companion planting:
- Find your USDA hardiness zone
- Select plants that do well in your zone
- Choose the plants that fit each niche or layer in the graphic above (canopy, understory, herb layer, etc.)
- Plant support species first to establish a microclimate and build the soil. For example, before planting fruit trees, grow nitrogen-fixing trees, shrubs, and flowers. Plant one nitrogen fixer for each productive plant (such as fruit trees or berry bushes).
Now, let’s take a look at the best companion plants, their benefits, and other tips to place them in your garden.
1. Brassicas
Brassicas are a huge friend and companion to the allium family. Pretty much any brassica will work when interplanted with alliums, including:
- Broccoli
- Cabbage
- Cauliflower
- Kale
- Brussels Sprouts
- Kohlrabi
- Bok Choy
- Mustard
- Rutabaga
Alliums and brassicas are one of the best pairings largely because brassicas are highly vulnerable to pests and disease.
For example, compared to growing rows of solely cabbage (aka monoculture), when onions and cabbage are interplanted, the onions repel many cabbage pests.
Here’s one study that found great results of this pairing.
Significantly fewer Bemisia tabaci (whitefly), Hellula undalis (cabbage moth) and Brevicoryne brassicae (cabbage aphid) infested the intercropped plants than the sole crop.
Canadian Center of Science and Education (CCSE)
And this isn’t true for just cabbages. Since all brassicas are closely related, the same if not better results can be had with the other brassicas.
Other companions for brassicas include celery, legumes, and clover. However, legumes (including clover) shouldn’t be planted near alliums as they compete.
Also, avoid planting brassicas with nightshade. However, you can use a “neutral” plant (such as lettuce) as a barrier in-between competing plants.
You can also check out brassica’s companion plants.
2. Nightshade
Nightshade plants benefit alliums by breaking up clay soil, shading the soil, and retaining water. The fruiting varieties of nightshade also attract pollinators for the alliums when they begin to flower.
Plants in the nightshade family include:
- Potatoes
- Tomatoes
- Peppers
- Eggplant
As with brassicas, alliums benefit nightshade plants greatly by increasing their pest and disease resistance, especially against Verticillium wilt.
The results showed that companion cropping with potato onion could alleviate the incidence and severity of tomato Verticillium wilt. The further studies revealed that the root exudates from tomato companied with potato onion significantly inhibited the mycelia growth and spore germination of V. dahliae.
Department of Horticulture, Northeast Agricultural University
Other good companions for nightshade plants include carrots, basil, and oregano.
Keep in mind that even though nightshades go exceptionally well with alliums, nightshades often cause trouble for other plants, such as fruit trees. The problems usually occur from encouraging pests and diseases (such as Verticillium wilt) for these plants.
Overall, avoid planting nightshades with most fruit trees, legumes, walnut, brassicas, corn, fennel, and dill.
3. Strawberries
Strawberries are one of the best companion plants with alliums because, as with nightshade, alliums help prevent and limit pests and diseases like Verticillium wilt.
A study performed in 2019 found that intercropping garlic with strawberries reduced pests, without affecting yield.
Our results showed that intercropping garlic and strawberry did not reduce both crops yield, therefore, improving land equivalent ratio and gross income to farmers.
Departamento de Agronomia, Universidade Estadual de Londrina (UEL), 86060070, Londrina, PR, Brasil.
So, even though yields of garlic and strawberries weren’t increased by intercropping, the pest resistance proved a good investment to the crop density and income. This helps correct the belief that interplanting negatively affects yields.
Strawberries also provide alliums with benefits such as increased pollination from their flowers, along with providing a ground cover. As a result, more of the allium’s flowers can be successfully fertilized and the plant’s soil has greatly reduced evaporation from the living ground cover.
Also, consider planting strawberry plants with borage.
For example, a recent study showed that borage interplanted with strawberries saw an increase in strawberry production, with 35% more fruits and 32% more yield by weight.
Other companions for strawberry plants include asparagus, sage, and thyme. Avoid planting strawberries with mint, cabbage, and melons.
4. Fruit Trees
Fruit trees assist alliums by attracting more pollinators, shading the soil, holding groundwater, breaking up compact soil, and providing mulch (from their branches and leaves). Alliums also grow great in the partial shade of fruit trees. As a result, these two are one of the best companion plant pairings out there.
Like most of the plants on this list, alliums benefit fruit trees by increased pest and disease including repelling mice, rats, deer, and other critters.
It’s believed that the sulfur from alliums helps prevent some fruit tree diseases to some extent. For example, a common companion plant pairing is interplanting chives near apple trees to prevent scab (source).
Also, if fungal or bacterial diseases do take hold, garlic cloves can be mixed into organic sprays along with neem oil and applied as a treatment in some cases.
Wildflowers are another companion for fruit trees and alliums.
5. Carrots
Carrots are biennial root vegetables, but are commonly grown as annuals, and grow in zones 3-10. They help other plants like alliums by breaking up compact soils and repelling some pests such as onion flies.
Keep in mind that carrots need rich, loose, and well-draining soil. It’s fairly common for carrot growers to accidentally get baby carrots because the ground is too hard or compact for the root to grow (this happened to us).
However, the ground will loosen naturally over time as the roots of plants penetrate it. Roots are also great at slowing and holding groundwater.
Pro-tip: You can cut the carrot tops off and replant them. They’ll quickly regrow new carrot roots!
Along with alliums, plant carrots with tomatoes, lettuce, and legumes. Avoid planting carrots near radish, parsnip, and dill.
6. Rosemary
Rosemary is natively from the Mediterranean, making it a good drought-tolerant plant. It attracts pollinators and repels pests such as slugs and snails through its high-resin flowers and leaves (source).
Since rosemary can grow into a fairly tall bush, it’s best to plant it a few feet away from your alliums. As long as you plant it within 25 feet of your alliums, you’ll get most, if not all of its benefits.
You can also take cuttings of your rosemary plant, bundle them, tie them with twine, and hang them upside down to dry them out and store them for later.
Lavender and sage also share similar pest resistance to rosemary, especially with slugs and snails, but avoid interplanting sage with alliums.
7. Lettuce
Lettuce is also native to the Mediterranean and is hardy, growing in zones 2-11. However, since lettuce is especially vulnerable to pests such as aphids, interplanting with alliums is highly beneficial.
To further combat aphids, you can plant companion flowers nearby such as nasturtiums, sunflowers, dill, calendula, and cosmos.
Other companions for lettuce include legumes, beets, radish, and carrots. Additionally, interplanting lettuce with broccoli improves both plants’ yields (source).
Avoid planting lettuce with parsley, celery, and cabbage.
8. Cucumbers
Cucumbers are highly susceptible to many pests including aphids, whiteflies, and cucumber beetles. Fortunately, these pests are repelled by the strong scent of alliums.
While cucumbers can grow horizontally along the ground, they do well when grown vertically. You can use a trellis, frame, or even a tree.
For example, in our garden, I grew cucumbers up a trellis on the west side of our tomatoes to provide the tomatoes with much-needed shade from the hot afternoon sun (it’s difficult to see, but here’s an image of when they were starting to grow).
When grown on a trellis, cucumbers benefit alliums by creating partial shade, attracting pollinators, and deterring some pests with their spiky leaves and fruit.
Other companions for cucumbers include corn, dill, legumes, and marigolds. Because of their large, shading leaves and vining aspect, cucumbers are also a great companion to use in Three Sisters gardens.
9. Chamomile
Chamomile is a great companion plant for alliums because it’s easy to grow, fixes nitrogen in the soil, attracts beneficial insects, and grows well in partial shade.
There are two main types of chamomile: German (Maricaria recutita) and Roman (Anthemis nobilis). Both are beneficial to have as companion plants.
First, chamomile helps fix the nitrogen in the soil by promoting beneficial bacteria to store nitrates in the soil (similar to comfrey). Their flowers also attract beneficial insects such as hoverflies, ladybugs, beneficial wasps, and honey bees.
If you’re not already aware, many of these bugs are helpful since they are predatory to common pests. For example, ladybugs are a natural predator of aphids and will help keep their populations down.
Chamomile also grows well with mint and basil. You can also make chamomile tea with its flowers. The more common variety to use for this is Matricaria chamomilla.
10. Dill
Dill is part of the parsley and celery family and is native to the Mediterranean—making it a drought-tolerant herb.
One of the most well-known companion qualities of dill is its ability to attract pollinators and beneficial insects such as ladybugs (which feed on spider mites and aphids). So if your garden commonly gets aphids, plant lots of dill!
You can also use dill in your garden to repel pests including cabbage loopers (source).
Plant dill with brassicas, lettuce, onions, corn, cucumbers, and fennel. However, avoid planting dill with carrots, caraway, and nightshade.
Other herbs that also work well with alliums include marjoram, mint, and parsley.
To see more companion herbs, check out my other post: The 10 Best Companion Herbs.
What Not To Plant With Alliums
While alliums benefit almost every plant, there are a few that they compete with. Avoid planting alliums with legumes, asparagus, sage, and other alliums. Generally, keep onions with onions, garlic with garlic, and so on.
