Companion Planting Onions

The garden is a battleground and your crops are your troops. Some of them work well together while others are enemies. Among your most useful enlisted soldiers are your onions.

Onion plants have the ability to improve the flavor of their companion plants and also provide defense by deterring pests like aphids, Japanese beetles, and rabbits.

Let’s look at which “troops” work best with your onions on the front lines of your garden patch.

What To Plant Next To Onions

  • Brassicas– Broccoli, kale, cauliflower, turnips, kohlrabi, and Brussels sprouts are all brassica vegetables that will benefit by being planted next to onions. Onion plants play marksman with most of the pests that give brassica crops trouble.
  • Lettuce, Swiss Chard, Arugula – Onions have relatively shallow root systems, so the ground soil close to the surface needs to be moist. The large leaves of these greens can preserve the moisture of the ground so that onions can thrive. Also, onion plants are notorious for being weak competitors to weeds. Since you’ll need to be picking plants out from around the top growth of onion plants it might as well be plenty of leafy greens that you can take back to the kitchen with you.
  • Chamomile -The antibacterial and antifungal properties of this plant are nice, but that’s not why you’re planting them next to your onions. Chamomile can improve the flavor of onions when planted in close proximity.
  • Summer Savory – If you have summer savory growing next to your onions, you might get sweeter onions. Your onions will also grow stronger and faster, as the savory encourages their growth.
  • Carrots – The natural aromas of the onion provide a sort of smokescreen for carrots giving off odor that masks the carrots from carrot flies.
  • Leeks – Plants from the same family don’t always make good companions in the garden, but there are some exceptions, such as leeks growing with onions. They have similar environmental needs, both requiring similar nutrients, and leeks will confuse the senses of onion flies.
  • Beets – Beets will appreciate having onions nearby since they provide a natural deterrent for garden pests like aphids and sugar-beet fly beetles. The deterrent protection extends to larger mammal pests like rabbits and deer.
  • Strawberries – Strawberries are among the most vulnerable crops in the garden to pests. Aphids love them and so do diseases. The sweet smell of ripe strawberries doesn’t help the soft bellied fruits situation any. The pungent odor of onions planted nearby can help keep strawberries safe.
  • Tomatoes – Tomatoes have similar problems to strawberries in that they’re vulnerable and their ripe smell advertises their presence. The strong smell of onions will help mask that juicy tomato smell.
  • Marigolds – Like onions, marigolds have a strong aroma. The difference is that onions do not attract pollinators the way marigolds do. Plus marigolds will attract beneficial insects that will lend their pest-devouring ways to other plants in the garden. Hoverflies and Lacewings that come for the nectar and pollen might stay for the aphids.

What Not To Plant Next To Onions

  • Other Onions, Garlic, Shallots – This might sound backward, but much of it has to do with issues that the plants have in common such as onion maggots. When onions are spaced close to other onions and their kinfolk such as garlic and shallots, the onion maggots will have no trouble traveling from one plant to another.
  • Peas, Pole beans, Bush beans – Onions are traditionally believed to be antagonists to beans and peas. They either stunt or negatively affect their growth. This is due to the fact that onions have been found to kill off the beneficial nitrogen-fixing bacteria present on the root nodes of beans and peas. Onions have potent antibacterial properties, and these properties don’t discriminate between “bad” bacteria that could harm the onions’ growth and the good bacteria that provide nitrogen to the soil courtesy of legumes. Not only that, it’s believed that some onion exudates, which are substances excreted by plant roots, can be absorbed by pea and bean plants which might give you bitter, onion-tasting legumes.
  • Asparagus – It’s been found that onions will stunt the growth of asparagus. As far as I can find there’s no concrete proof of this but it might be a good idea still to keep them at respectable distances apart in the garden.

Planting Tomatoes and Onions Together

Tomatoes practically paint a bullseye on themselves in the garden. Between the sweet, juicy aroma of the tomatoes and their bright red coloring, they’re practically begging for unwanted attention.

Planting onions with your tomatoes will lend some of the onions’ strong smell to confusing or deterring would-be predators, such as aphids.

Companion planting straddles a crossroads between science and folklore. The only way to be sure what does well with your onions is to experiment!

Please comment below with your own thoughts on companion planting onions.

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