By Sarah Wilson
Choosing the right companion plants for onions is easy to do and means you will be able to grow more of them and they will be better quality too. Certain combinations of plants grown together can even provide a healthier growing environment. Stick with a few tried-and-tested combinations and you'll boost your onion crop in no time.
Onions punch above their weight when it comes to companion planting. As they are a natural pest deterrent and keep aphids and other problem bugs at bay there’s a long list of other crops keen to mix with them.
They also make great planting companions due to their ability to improve the flavor of other plants near them. Find out which other vegetables, herbs and flowers make good companion plants for onions and help to attract beneficial insects and produce the best harvest too.
Not all plants make good companions though as some varieties (like spring onions and chives surprisingly, even though they're members of the same family) do not get on if they’re planted together.
So if you're learning how to grow onions you’ll want to make sure you know the best companion plants for them so you can plan some combinations that really work.
Why should you use companion plants for onions?
It’s a tried and tested formula: plant your onion crop next to different herbs, flowers or vegetables that are known to benefit them as they grow and reap the rewards with a bumper harvest of healthy veg for the pot. Onions are great companion plants for helping their neighbours avoid pests and keeping fungal infections away.
Interplanting onions with the right companions reduces the chances of your veg being attacked by pests like onion maggots. Try different combinations and arrangements of companion planting for onions and choose a layout that complements the look of your raised garden bed ideas too. It’s also important to plant crops that don’t compete for nutrients.
The best companion plants for onions help create a balanced ecosystem in your garden too that encourages lush growth and boosts the flavor of your produce. Introducing companion plants for onions is a natural way of combating pests and diseases and at the same time helps to encourage beneficial insect diversity to enhance the garden plot.
Find out what onions prefer to be planted next to and give your crop a headstart for your best growing season ever.
Best herb companion plants for onions
Certain herbs can be a brilliant option for companion planting for onions. Their scent can attract pollinators as well as deter pests that can destroy your onion crop. Try adding one or more of these to your kitchen garden ideas.
Along with its antibacterial and antifungal properties, chamomile also improves the flavor of onions when planted close by and its daisy-like flowers are pretty to look at too. This makes it a great choice when it comes to choosing companion plants for onions.
Chamomile is often recommended as a companion plant in the vegetable garden as its sweet fragrance welcomes beneficial pollinators as well as keeping pests away.
2. Summer savory
Plant some savory around your onions and it can encourage their growth as well as helping to make them sweeter tasting. Savory loves well-drained soil and plenty of sun just like onions so they make natural partners.
Savory looks a bit like thyme and has a similar peppery taste. There is also a winter variety, which has a much stronger taste.
If you want to learn how to create a herb garden savory makes an unusual choice to add to the mix.
If you're also learning how to grow mint, then you might like to know that its aromatic leaves help to confuse and deter onion fly, so it’s a great one to grow alongside your onion crop.
Remember to plant it in pots to dot around near your onions though instead of in the ground as it's rampant if you don't restrain it.
Best flower companion plants for onions
There are some flowers that will work well alongside your onion crops. Not only can they help to improve your onions, they will add a pretty display in your potager garden, too.
Marigolds are great companion plants for onions. Grow them in between your vegetables as they're known for repelling aphids due to their strong scent, which works as a natural deterrent.
These strongly scented flowers are useful for attracting beneficial insects that can pollinate your veg plot too, as well as feeding on the various pests that may be causing problems with your fresh produce.
Find out how to grow marigolds and you'll soon be giving your onions a helping hand. The good news is that once established there’s very little else you need to do with marigolds as they're a low-maintenance summer planting choice.
Planting onions in amongst your rose plants can be a simple way to deter pests from attacking your roses. The strong scent from the onions can be used as a method for how to get rid of aphids as it helps to mask the scent from the roses. This creates some confusion for pests and therefore offers an element of protection for your precious blooms.
Best vegetable companion plants for onions
Looking for other vegetables to grow alongside your onions? These options will grow well alongside your onion crop, and can offer many benefits, too.
Plants in the whole cabbage family, which includes broccoli, kale, cauliflower, turnips, kohlrabi and brussels sprouts, make great companion plants for onions as they like the same soil conditions and sunny position in the garden.
The cabbages benefit because onions are good at repelling cabbage worms, weevils and cabbage maggots. The scent of onions also helps to deter rabbits on the loose in the veg patch looking for leafy greens to munch through.
If you're learning how to grow carrots, planting onions and spring onions alongside them is a classic combination that is tried and tested. The smell of onions deters carrot root fly while the smell of the carrots helps to deter onion fly, so both crops benefit from the pairing.
There's more tips on the best companion plants for carrots in our dedicated guide.
While the rest of the onion family are out of bounds, leeks make good companion plants for onions due to their similar nutrient needs. Leeks are also effective at confusing onion flies.
Check out more tips on how to grow leeks and give your veg patch a head start.
Beets benefit greatly from companion planting for onions and vice versa. Onions can be a natural deterrent for garden pests like aphids and beet flea beetles, as well as deterring rabbits which love to eat them.
Companion planting beetroot with onions also helps to protect the onions from thrip. This is a small black winged insect which sucks plant sap and can be a serious pest to onions when present in large numbers. Find out more about how to grow beetroot if you want a successful crop.
Sometimes companion planting is about how best to utilize space too, especially if you're on the lookout for small vegetable garden ideas. Lettuce and onion crops can be planted happily next to one another without competing for resources, allowing you to make the most of planting space in your vegetable garden.
Upright onions utilize underground space to grow, with their roots reaching down into the earth, so planting shallow rooted lettuce between the rows works well and also cuts down on the amount of weeding needed as their broad leaves cover the soil and act as a weed suppressant. It's a win-win.
Onions could soon be your new best friend if you're learning how to grow tomatoes. Due to their strong scent, onions help to deter aphids and Japanese beetles, which helps prevent your tomato plants being destroyed.
There's more tips on our top companion plants for tomatoes in our dedicated guide, too.
What not to plant with onions
Although onions are happy to grow alongside lots of other crops, there are a few that they don't get along with.
Some varieties of vegetables will compete for space, light, water, and soil nutrients. Or in some cases, they will attract insects that are detrimental. This means they're not great companion plants for onions.
So, when choosing companion plants for onions, stay clear of the following:
- Other plants in the onion family such as garlic and shallots are common targets of onion maggots as well. Avoid planting them near onions so onion maggots can’t spread easily from plant to plant if they're crowded closely together. There's tips on the best methods for how to grow garlic in our guide.
- Chives are also close relatives of the onion family and for the same reasons other members of their family aren’t good neighbors, and onions fall into this category.
- Most varieties of peas and beans are harmful when planted close to onions. Beans are considered allelopathic plants, which means they produce biochemicals that can hinder the growth of other plants. Beans and peas do not mix well with members of the onion family including onions, leeks, chives and garlic.
- Sage has some strong dislikes when it comes to companion plants and that includes onions too. Onions prefer moist soil, which won't work for sage as it likes a drier growing medium.
- Learning how to grow asparagus? Avoid growing it with onions. Grown together in the same bed can lead to stunted growth as they like different conditions. This means that for one to thrive, the other will not.
Sarah Wilson has been a lifestyle journalist for many years, writing about gardens since 2015. She's written for Gardeningetc.com, Livingetc, Homes & Gardens, as well as Country Homes & Interiors and Modern Gardens magazines.
Her own (small urban) garden is a work in progress - so many ideas, not enough space to cram them in. Hero plants include her ever growing collection of ornamental grasses, black bamboo and ferns, and the perennials like salvias and penstemons that come back reliably year after year. All very restrained though when in fact she'd love to pack her garden with gaudy dahlias and giant cannas, so these are top of her wish list for what to grow next.
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