Planning out your garden or allotment beds to plant certain varieties or types of plants near one another offers many natural benefits. This is known as companion planting and can help to thwart pests, attract helpful pollinators and may even improve the flavour of your veg come harvest time. In this guide, we discuss what to plant with onions to benefit other plants and the onions themselves, as well as the advantages of onion crop rotation.
What grows well with onions?
There is a vast range of companion plants for onions that are worthwhile in planning for your growing space. This can help to provide benefits for various other plants in your growing space as a result of their proximity to onions. Additionally, there are also many plants that can benefit onions when planted near onion sets.Plants That Benefit From Onions
Onions can be very effective as a companion plant to other crops because the strong smell helps to deter pests. The smell of onions can protect against insect pests such as aphids as well as larger visitors to your patch like rabbits.Plants that can be helped along by proximity to onions include:
- Brassicas - Onions help to deter cabbage worms, loopers and maggots. Options of brassica plants include broccoli, kale, cauliflower, turnips, and Brussels sprouts, as well as traditional cabbage.
- Carrots - Onions have a repellent effect on carrot fly which can affect carrot seeds after growth.
- Beetroot - As a natural deterrent of aphids, sugar beet-flea beetles, rabbits and deer, onions can help to keep your beetroot plants protected.
- Strawberries - A notoriously vulnerable crop, strawberry plants can fare better when planted near onions to repel aphids.
- Tomatoes - Another favourite of many insect pests, tomato plants can be protected by nearby onions.
Plants That Benefit Onion Growth
It’s also the case that other crops can have benefits for onions if planted in close proximity, bringing advantages in growing conditions, flavour and pest-repelling ability. These onion plant companions include:- Chamomile - As well as being good to grow for a cup of tea, this herb plant can help to improve the flavour of onions when grown close by.
- Summer savory - Sowing some of these classic herb seeds helps to sweeten your onions and encourage their growth.
- Leeks - Despite being a part of the same family, leek plants are great at confusing onion flies, helping to protect your crop. They also have similar requirements in terms of growing conditions.
- Swiss chard - With large leaves, chard plants can provide shade over the surrounding soil, helping to keep it moist. This encourages beneficial growing conditions for your onions. Planting onions with swiss chard makes for a mutually beneficial relationship as onions help to protect the swiss chard from pests.
You should also consider other plant combinations that aren’t directly beneficial to each other but can be helpful in other ways. For instance, lettuce plants provide few benefits to onions and vice versa, except that the two plants have differing root depths. This means that lettuce won’t compete with your onions for nutrients, so they can be planted closer together in order to maximise your use of space in the garden.
Can You Plant Onions Next to Potatoes?
Though there is a wide range of onion plant companions that work excellently as mentioned above, onions and potatoes are not an effective combination.
Both require different growing conditions, as onions require neutral or slightly alkaline soil, while potatoes need slightly acidic soil. They can also negatively affect each other by competing for nutrients, as both are heavy feeders and attract different pests, which could cause pest problems to increase. Planting potatoes after onions for crop rotation, however, can work if the soil’s pH is lowered with organic matter such as pine needles, leaf mould or sulphur.
Can you plant onions in the same place every year?
When plants of the same family are planted in the same spot year after year, the soil can become deprived of the nutrients that the family uses the most. This can then affect the quality and quantity of harvested crops in the long run.
The risk of plant-specific, soil-borne diseases can also increase when onions are planted in the same place. For this reason, it’s recommended not to plant onions, shallots or garlic in the same bed every year. It also helps to reduce the build-up of pests that attack the onion family, as their numbers will decline during times when onion plants aren’t present.
The Benefits of Onion Crop Rotation
To combat the above-mentioned problems, it is best to practise onion crop rotation. This process involves rotating different families of plants in order to balance out the soil deprivation. This way, when you add new nutrients using garden compost or fertiliser, for instance, you bring it back up to a higher, more balanced level rather than making the soil too rich in certain nutrients.
A sample rotation could look like this for examples of what follows onions in crop rotation:
- Year one: Onions
- Year two: Brassicas
- Year three: Potatoes
Instead of missing out on onions for a couple of years while your other crops are growing, you can set up three beds and create a cycle where each crop moves to the next bed for the following year.
Shop Quality Onion Sets at D.T. Brown
To grow healthy onions that are full of flavour, you can find many onion sets in a range of cultivars at D.T. Brown. These are disease and virus-free and chosen for their quality, so you can grow our onion sets with confidence. With over 100 years of experience in providing gardeners with exceptional vegetable plants and vegetable seeds, you can rely on our bulbs to grow vigorously in your garden.For further advice on onion cultivation, you can find our guides on how to grow onion sets and how to grow onions from seed to find in-depth guidance on each stage of growing.
If you’d like to know more about our range of fruit plants, flower plants, or anything else from our extensive range of gardening supplies, contact us today and a member of our team will be happy to help you.
