Are there any bad companion plants for onions? Turns out there are. While companion planting is an old-age technique of planting two or more plants together to maximize their potential, there are some combos you’d want to stay away from.

Bad Companion Plants for Onions

If you want to grow the most delicious onions in your vegetable garden this summer, there are some plants you shouldn’t consider as onion companions, and here we bring them all.

Bad Onion Companion Plants List – Covering All the Aspects

Companion planting is the art of planting compatible plants together and has been used by gardeners for centuries to maximize their growth potential, help plants withstand pests and diseases, and increase their overall health.

By planting onions with other plants, you can help to create a symbiotic relationship that will benefit both the onions and their companion plants.

Just as there are certain plants that are ideal companions for onions, there are also certain plants that should be avoided when companion planting with onions.

Each of these plants has specific drawbacks that make them poor companions for onions.

1. Peas

Onion cause damage to the pea plant

Growing Season Summer
Distinguish Characteristics 
  • Vining Plant
  • Small green veined leaves
  • Green pods
Specific Needs
  • Acid and alkaline, clay soils
  • Full sun
Common Pests 
  • Aphids, leaf miners
  • Mosaic virus, grey mold, pea wilt

Pisum sativum or more commonly known as a pea is a plant grown for its beautiful and flavorful seeds and seedpods. They are incredibly easy growers and are a valuable food source for cuisines across the globe.

The pea fruit is packed with vitamins, minerals, and other healthy micronutrients!

But if you’d want your onion and peas to grow happily, they should each be placed in the corner of their own.

It’s not so much that peas are bad for onions, but it’s the other way around. If you plant onion next to peas, it may cause damage to the pea plant.

Peas are susceptible to the same pests that onions will attract, and you’ll be left with no pods in the season you grow them together.

On the other hand, peas fill the soil with nitrogen, which in large quantities, can stunt the growth of your onion plants.

2. Beans

Onions are poor companion plants to beans

Growing season Spring to early Summer
Distinguish characteristics 
  • Tall and low growing
  • Green pods
  • Fleshy leaves
Specific needs
  • moist but well-drained soil
  • Warm soil temperatures
Common pests 
  • Slugs
  • Snails 
  • Beetles, mites, and aphids

Pole beans are annual garden plants that are grown for their edible bean pods. The entire plant is often used, with leaves being edible too.

Bush Beans are very similar to previously mentioned beans, except these grow on bushier and somewhat shorter plants. This bushy variety often stays below two feet tall, making it a desirable companion plant option for many garden cultures.

But you shouldn’t plant them together with your onions.

Onions are poor companion plants to beans as much as beans are to them! Onion plants inhibit the growth of all bean plants because onions release a substance that reduces the beneficial bacteria population essential for bean nutrition and healthy root growth.

In such a state, bean plants cannot release enough nitrogen into the soil, which will affect the whole bunch of plants you grow in their vicinity, including onions.

3. Asparagus

Asparagus poor companion planting option for Onions

Growing Season Early Spring
Distinguish Characteristics 
  • Tall and low growing
  • Green pods
  • Fleshy leaves
Specific Needs
  • moist but well-drained soil
  • Warm soil temperatures
Common Pests 
  • Slugs
  • Snails 
  • Beetles, mites, and aphids

Asparagus is a widely known plant, appreciated for its juicy and delicious young shoots known as spears. It is a long-lived perennial plant that has highly ornamental tall and feathery foliage.

It’s widely grown as a vegetable, and it is one of the first vegetables that are crop ready every year, producing the majority of the growth in the early spring!

Only young Asparagus spears are eaten. If not picked on time, they will turn woody and won’t be as nutritious.

Alliums are a very poor companion planting option for asparagus. Leeks, garlic, and onion can stunt asparagus growth, and you should plant the two varieties as far as possible from each other!

In turn, asparagus can invite a whole range of beetles into the garden, which may feed on your onions.

Along with pests, Asparagus is prone to fungi, wilt, and rust, along with plenty of viruses, which can poorly influence the growth of your onions.

4. Sage

Onions aren’t good companion plants for sage

Growing Season Spring And Summer
Distinguish Characteristics 
  • Tall perennials
  • White and silvery green foliage
  • Pleasant smell
Specific Needs
  • well-drained soil
  • Full sun
Common Pests 
  • Slugs, Beetles
  • Root rot, wilt

Sage is grown for its beautiful silver and white foliage. It is a fast-growing perennial adding light and adorable contrast to the landscape, and grows perfectly well with almost anything except onions, and you’ll soon find out why.

Sage is growing in bushy clumps, and the foliage is dashingly aromatic when scratched or bruised. The leaves are wooly on the underside and glabrous at the top. Sage thrives in moderately fertile and poor soils and full sun.

If you grow onions next to sage, you may want to rethink your strategy!

Onions aren’t good companion plants for sage, as they will require a lot more water than the sage plant and can cause overwatering problems and stunted growth in sage plants.

If grown in well-drained soil, sage will rarely have pest issues, but combined with the moist environment of an onion, it will attract slugs, bugs, root rot, and wilt, which will all affect and damage your onion crops in turn.

5. Other Alliums

not plant different allium species together

Growing Season Spring to Summer
Distinguish Characteristics 
  • Bulby plants
  • Edible roots and top shoots
  • Flavorful plants
Specific Needs
  • moist but well-drained soil
  • Full sun
Common Pests 
  • Slugs, Snails, onion rot maggot, thrips
  • Onion rot, rust, mildew

Alliums are considered a staple food in kitchens across the globe. Alliums are a broad family that includes plants like onions, garlic, shallot, and leeks!

Onions have been cultivated for at least 5000 years and provide an awesome fragrance and flavor to any meal.

Generally, alliums are easy to grow from either seed or propagated from bulbs. They perform best in moist and well-drained soils under full sun, with an ideal pH of between 6.0 and 7.0.

Onions and alliums are, in general, considered a very good neighboring family to most plants.

However, you shouldn’t plant different allium species with other alliums, such as garlic, and different onion plants can attract onion maggots to each other and decimate their population.

Not to mention the many onion diseases they can spread amongst each other!

6. Parsley

Parsley is a nutrient-hungry plant

Growing Season Spring To Fall
Distinguish Characteristics 
  • Bushy biennial 
  • Nice smell
  • Fine leaves
Specific Needs
  • Moist and fertile area
  • Full sun
Common Pests 
  • Slugs, Beetles, Weevils
  • Root rot, stem rot, leaf spots

Parsley is a bushy perennial with a dense rosette of aromatic leaves which we all love. Native to the Mediterranean, the parsley plant will bloom in the second year of growth by sending up stalks of small yellow flowers up their stems.

Usually, parsley leaves become more coarse in their second year of growth, but they do lose much of their original strong flavor in this period. In general, parsley leaves are full of vitamins and minerals and are best used in soups and other healthy meals. 

Parsley plants grow up to 12 inches tall. They perform best in fertile and moist areas under full sun. Be careful where you grow them, though, as they can be toxic to animals and cause your onions not to grow as expected!

Parsley is a nutrient-hungry plant and will fight for nutrients with allium plants. If you have onions planted on the same patch of land as parsley, this will set the two for disaster. On top of that, parsley can attract diseases and pests such as leaf spots, stem rot, weevils, and flea beetles, which definitely won’t be shy about jumping onto your onion plants.


Companion planting is an age-old practice of planting two or more plants together to maximize their growth potential. Don’t forget to do your research when it comes to companion planting with onions, and make sure to avoid the worst companion plants for onions!

  • Of the worst companion plants for your onions, we have to mention peas, beans, asparagus, and other alliums. While sage isn’t exactly a poor companion, the soil choices you make for the onions definitely won’t cater to your sage plants.
  • Onion plants grow swimmingly well with leafy greens such as cabbage, leeks, beets, and lettuce.
  • If you’d like to add to the growth of your onions, definitely go with some beautiful garden herbs, such as summer savory! Plant onions next to this one and see them flourish.

Companion planting is a great way to maximize the potential of your crops. By planting compatible plants together, you can help to create an environment that is beneficial for both the onion and its partner plant!

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