Onions are an excellent addition to any garden, offering a multitude of benefits that extend beyond their culinary uses. When planted alongside other crops, onions form valuable relationships, enhancing the flavor of nearby vegetables while repelling pests that might otherwise damage your harvest. With their ease of cultivation and monetary value, it’s no surprise that many gardeners consider onions a prime choice for their plots.
Not only do onions prove simple to grow, but they also serve as a valuable cash crop, making them an attractive option for those looking to maximize the yield from their land. As if these benefits weren’t enough, onions are a staple ingredient in countless recipes, ensuring that you’ll never struggle to find uses for your bounty.
If you’re interested in getting the most out of your onion crop by embracing companion planting, it’s essential to understand which vegetables pair well with onions and which might detract from their growth. By carefully selecting what to plant alongside your onions, you can create a thriving garden ecosystem that rewards your efforts.
Best Companion Plants for Onions
Onions thrive in full sun, with no tolerance for shading from other plants. Their ideal soil environment features a pH between 6 and 7, and it’s essential that the soil drains well – wet conditions can lead to rot. A temperature range of 55°F to 75°F is also crucial for optimal growth. With these requirements met, onions can flourish.In terms of companion planting, some excellent options include
Carrots
The humble onion has an unexpected benefit when it comes to its fellow vegetable, the carrot. Specifically, onions can help deter the pesky carrot fly from targeting your prized carrot crop. By planting onions around the perimeter of your carrot patch or alternating rows of carrots with onions, you can create a natural barrier that keeps these unwanted pests at bay. The pungent aroma of onions is apparently unappealing to the carrot fly, making them an effective companion plant in this context.
Beets
When it comes to gardening, one effective way to repel pests is by incorporating onions into your planting strategy. Specifically, pairing onions with pest-prone plants like beets (Beta vulgaris) can be a winning combination. Beets are susceptible to aphids and sugar beet beetles, which are deterred by the sulfur-like aroma emitted by onions.
If you’re struggling to keep rabbits, hares, and deer from munching on your beet leaves, planting plenty of onions around them can be an effective solution. I find it helpful to position the beets towards the center of the planting area, surrounded by rows of various onion varieties. Just ensure that you have sufficient access to tend to the beets as needed.
Swiss Chard
When incorporating Swiss chard (Beta vulgaris subsp. vulgaris) into your garden, consider its unique ability to provide a moderate amount of shade that can help maintain soil moisture. As an added benefit, this shade won’t hinder sunlight from reaching onions, as the chard’s growth is relatively contained. Onions, with their shallow root systems, thrive in moist but not waterlogged soil conditions. The companion planting effect of Swiss chard helps achieve this ideal environment.
To reap these benefits, plant the chard among onion rows, leaving a 12-inch buffer between the two at its base. Alternatively, you could position the chard behind the onions if your garden faces the afternoon sun, allowing for optimal sunlight penetration while still providing some shade.
Leeks
When planning your garden, it’s generally recommended to diversify by not grouping plants from the same family together. This is because similar plants can attract similar pests and diseases. However, there are some exceptions to this rule. For instance, leeks (Allium ampeloprasum) and onions have a lot in common. They share similar soil, temperature, and nutrient requirements, making it easy to grow them together.
In fact, leeks can even provide a natural defense for your onions by confusing onion flies that might be looking for a meal. One strategy is to plant alternate rows of leeks and onions, or to intersperse rows of onions with rows of leeks. This way, you can enjoy the benefits of growing these two plants together without sacrificing their individual health.
Summer Savory
While some companion plantings provide protection for crops, others work to enhance their quality and yield. One example is summer savory (Satureja hortensis), which has a unique ability to sweeten onions and promote larger bulbs. As summer savory can grow quite tall – up to two feet – it’s essential to consider the impact of shade on your onion crop.
To optimize results, plant onions in a spot that receives direct sunlight and ensure both plants receive adequate moisture without waterlogging the soil.
Brassicas
Companion planting with onions has numerous benefits for the Brassica family, which includes cabbage, cauliflower, broccoli, kale, kohlrabi, and mustard plants. In fact, all of these vegetables thrive when planted alongside onions. One notable exception is turnips, which should be avoided as they can absorb the flavor of the onions. The association between Brassicas and onions also extends to pest control, as the strong scent of onions repels many pests that target these plants.
This natural deterrent can significantly reduce the need for pesticides, making it a valuable strategy for gardeners seeking to minimize their environmental impact.
Lettuce
When it comes to planting lettuce (Lactuca sativa) and onions, timing is everything. Unlike onions which require a bit more time to mature, lettuce grows swiftly, making it ideal to sow its seeds when the onions are still in their early stages of growth. By allowing the lettuce to flourish first, you’ll be able to harvest it before devoting space and attention to the onion bulbs as they develop.
An added benefit of this approach is that onions can help deter pests that target lettuce, such as slugs, snails, and aphids, effectively reducing the need for pesticides or other chemicals in your garden.
Strawberries
While it may seem unusual to pair onions and strawberries, this unique combination can actually benefit your strawberry plants. Onions won’t overpower the sweet flavor of strawberries, but they will help deter pests that commonly target them. To take advantage of this synergy, plant rows of strawberries alongside the onion patch, leaving about 12 inches of space between each row.
Chamomile
Not only does chamomile (Matricaria recutita and Anthemis nobilis) boast impressive benefits for herbal remedies and teas, but its unique characteristics also make it an excellent companion plant. When grown alongside onions, chamomile has been known to enhance the flavor of its pungent counterpart. Moreover, when planted together in the onion garden, chamomile’s robust growth is often facilitated by the favorable conditions.
Furthermore, during periods of high humidity, chamomile’s natural antifungal properties can prove particularly effective in preventing onions from contracting fungal diseases, thereby contributing to a healthier and more resilient crop.
Peppers (Hot and Sweet)
When it comes to maintaining a healthy pepper crop, onions play an unlikely yet crucial role in keeping those pesky pests at bay. Aphids and cutworms are notorious fans of young pepper plants, but they’re not too keen on onions either. By strategically planting peppers within 12 to 18 inches of onion rows, you can create a natural barrier that keeps these unwanted visitors from getting too close.
Melons
When it comes to growing melons, it’s interesting to note that certain pests are naturally repelled by the presence of onions. Specifically, melon aphids and spider mites are two common pests that are deterred by the strong scent and flavor of onions. As a result, planting onions alongside your melons can be an effective way to minimize infestations. Just be mindful of how you lay out your crop, as melon vines can quickly overpower onions if they’re planted too close together.
In fact, some melon varieties like honeydew, watermelon, and cantaloupe are particularly well-suited for co-planting with onions, so feel free to give it a try!
Radish
Radishes are often overlooked in gardening, but they have a unique ability to thrive in a variety of settings and can even benefit from being planted alongside other vegetables like onions. One effective way to incorporate radishes into your garden is by planting them among rows of onions or even between individual onion bulbs.
While there isn’t a significant advantage to either the onions or radishes themselves, this companion planting combination works well because radishes mature quickly and will be harvested before you even consider collecting the onions. In fact, you may be able to squeeze in two separate plantings of radishes without compromising the growth of your onion crop. Just be mindful not to disrupt the onion bulbs as you’re harvesting the radishes.
Parsnips
Parsnips (Pastinaca sativa) thrive when companion-planted with onions, much like carrots. This harmonious coexistence is due to the onions’ pungent scent, which deters pests that target parsnips and carrots alike. In my experience, having rows of onions flanked by rows of carrots on one side and parsnips on the other has proven to be a successful arrangement.
Dill
When cultivating Anethum graveolens, or Dill, alongside Allium cepa, commonly known as Onions, you’ll find that they coexist harmoniously. In fact, the presence of Dill can enhance the flavor profile of Onions, making it a valuable addition to your culinary repertoire, much like Onions themselves.
Borage
Borago officinalis, commonly known as borage, is a valuable addition to any garden, not only because of its edible flowers and leaves but also due to its ability to attract beneficial insects. One of the most significant benefits of growing borage is its capacity to draw in predatory wasps that target pests like onion destroyers, making it an excellent companion plant for crops.
This underutilized herb also demonstrates a natural resistance to cabbage worms and tomato worms, providing additional protection to other plants in your garden.
Marigolds
Marigolds (Tagetes spp.) have earned recognition for their ability to effectively deter aphids, making them an excellent choice for planting alongside onions. To further utilize their benefits, consider interspersing marigolds throughout the onion rows, or positioning them at the perimeter of your garden as a natural barrier against these pesky pests.
Mint
Mint’s potent aroma can be particularly effective in deterring onion flies, causing them to become disoriented due to its strong scent. It’s essential to consider mint’s invasive nature when planting it, as it has a tendency to spread quickly and dominate any surrounding area. To keep mint in check, I recommend potting it up and removing the containers at the end of the growing season.
Additionally, mint can be used to advantageously support neighboring tomato plants by placing its containers strategically between them. Just be mindful that mint’s roots shouldn’t escape through the container’s drainage holes and spread into the surrounding soil.
4 Plants to Avoid Putting With Onions
While onions can be a great addition to many gardens, they’re not the best companion for every plant. In fact, some plants don’t tolerate onion’s presence at all. If you’re looking to create a harmonious garden ecosystem, it’s essential to know which plants onions clash with. Here are four examples of plants that onions don’t play well with.
Legumes
It’s generally not recommended to combine onions and beans in the same garden bed. The chemicals released by onions can be detrimental to the growth of beans and other legumes, potentially stunting their development or even causing them to perish. This issue affects a range of legumes, including peas, lentils, alfalfa, clover, chickpeas, soybeans, and lupins. Legumes are known for their ability to enrich soil with nitrogen, making them valuable additions to any garden.
However, onions require a significant amount of nitrogen themselves, which can create a conflict when planting them alongside legumes. A more harmonious approach is to plant onions after legumes have had a chance to fix the soil with nitrogen.
Sage
When cultivating both sage and onions, it’s essential to recognize that each plant has distinct requirements. Sage, in particular, demands specific conditions that may not be suitable for onion growth. Conversely, optimal growing conditions for onions might not align with those needed by sage. To ensure a harmonious coexistence, it’s crucial to maintain a healthy distance between the two plants, allowing each to thrive under its preferred environment.
Asparagus
When growing onions and asparagus together, it’s essential to recognize that they compete for the same nutrients. Unless you’re constantly monitoring their growth, one crop will inevitably suffer at the expense of the other. Asparagus, in particular, requires a significant amount of time to establish itself and produce year after year. If you harvest onions too close to the asparagus, you risk disrupting its natural growth cycle.
This is especially important to consider when planning your garden layout and harvesting schedule.
Other Alliums (Except Leek)
When it comes to growing garlic, shallots, and onions, it’s crucial to maintain a clear distinction between these closely related plants. The reason lies in the pesky onion maggots that can wreak havoc on your entire crop. These unwanted visitors are notorious for migrating from onions to garlic and shallots, causing significant losses if left unchecked. To ensure a healthy harvest, make sure to keep these two crops well-separated from each other.
