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Good and Bad Onion Companion Plants

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Good and Bad Onion Companion Plants

When it comes to companion planting, it’s important to know which plants you can grow alongside onions and which ones should be avoided.

In this article, we’ll discuss some of the best and worst companion plants for onions, so you can maximize your onion harvest.

Good Companion Plants for Onions

Here is a list of the best plants to grow with onions in the vegetable garden.

  • Broccoli
  • Kale
  • Tomatoes
  • Brussels sprouts
  • Peppers
  • Chamomile
  • Summer savory
  • Pak choi
  • Carrots
  • Beets
  • Eggplant
  • Cucumbers
  • Lettuce
  • Amaranth
  • Thyme
  • Cabbage
  • Cauliflower
  • Strawberries
  • Swiss chard
  • Marigolds
  • Celery
  • Dill
  • Mint

Moreover, green onions (scallions) thrive next to many of these plants too.

What Not to Plant with Onions

Below are some of the worst plants to grow with onions. These may inhibit their growth and development and harbor pests, among other things.

  • Peas
  • Beans
  • Sage
  • Asparagus
  • Alfalfa
  • Clover
  • Wheat
  • Squash
  • Garlic
  • Shallots
  • Leeks

Wheat, clover, and alfalfa are bad companions because they may harbor onion thrips [1]. Squash, beans, garlic, shallots, peas, and leeks may also encourage bad insects.

How to Grow Onions

You can grow onions from seeds, sets, or scraps. When it comes to onion sets, these small bulbs are ideal for planting. Larger bulbs are more prone to bolting (flowering) earlier than smaller bulbs.

If using sets, plant them at a depth of 1 to 2 inches and a spacing of 2 to 6 inches. Additionally, separate rows 12 and 18 inches apart.

To grow from seed, start the seeds about 8 to 10 weeks before you plan to transplant them outside. As a general guideline, place seedling transplants 4 and 5 inches apart in rows of 12 to 18 inches wide.

Furthermore, onions thrive best in nutrient-rich soil and full sun. To provide space for bulb growth, thin out any plants that are becoming too thick in the planter.

You may use the young plants from the thinning as spring onions in the kitchen.

Care and Maintenance

Plants will begin developing bulbs in the summer when the temperature warms up.

When the leaves turn brown and droop over, onions are ready for harvesting. However, allow the onions to dry out in the garden for a few days before storing them.

Keep them in a cool, dry place until you’re ready to use them when the outer skin is dry and papery.


Long-day onions need at least 14 hours of direct sunlight each day to thrive well. On the other hand, short-day onions require at least 10 hours of sun per day [2].


In order to properly grow these plants, you need the right soil. The soil must be fertile, well-drained, loose, light, and loamy.

Additionally, incorporate a substantial amount of organic matter. The ideal soil pH range for onions is 6.0 to 7.0.


The plants require adequate water to sustain their growth. To avoid bulb rot, water once a week. However, don’t overwater them or leave them to sit in waterlogged soil.


Onions are heavy feeders. Therefore, in order to develop large bulbs, treat the plants every few weeks with a high-nitrogen fertilizer such as Nitrogreen.

This will support leaf growth. However, when the bulbs begin to push the earth away, stop feeding them.

Pests and Diseases 

Below are just a few of the pests and diseases that affect onion plants.


Neck rot, bulb rot, and leaf rot are common. To prevent rot, ensure that the soil is well-drained and aerated.


Onion thrips may cause damage to leaves and give them a white or silvery appearance. Soapy water and neem oil are great natural treatments for thrips.

Onion Root Maggots

At the base of the plant, onion flies lay their eggs. The maggots from these eggs then crawl deep into plant stems, where they feed on the roots and finally destroy the onion plants below the soil.

Rotate your plants every year to keep them free of pests. Diatomaceous earth also works.


The amount of time it will take for onions to develop varies. However, they may be harvested at any stage. Even seedlings that have been pulled from a row can be utilized as green onions.

When roughly half of the top leaves have fallen off and the skins of the bulbs have a papery texture, the bulbs are completely grown. You may achieve longer-lasting storage by allowing bulbs to stay in the ground until at least half of their green tips have fallen.

Allow the bulbs to dry out in the ground for a few days before removing them from the ground. Digging up the onion bulbs rather than plucking them out is a preferable strategy. Also, only a little digging is necessary to remove the residual roots.

Allow the bulbs to dry out in a warm, dry environment with sufficient air circulation while they finish curing. Don’t remove the leaves. You may use your fresh onions whenever you choose.

Where to Buy Seeds

Quality seeds are essential when you’re ready to start your plants from seed. Several local farm stores sell vegetable seeds of all kinds.

Additionally, you may purchase organic seeds of the highest quality from reliable internet retailers.


Onions are fairly easy to cultivate. However, knowing which vegetables, herbs, fruits, or flowers grow well with them is important.

Companion planting is a common practice for promoting garden well-being. You can naturally repel various pests, attract helpful insects, and boost plant growth by placing certain crops next to each other.

Use the list above to know exactly what to plant near onions as well as what not to plant next to them.

Sasha Brown

Sasha Brown is a blogger and lover of all things natural.

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