What is companion planting?
Companion planting is growing different crops together, choosing plants that benefit or complement each other. These may be planted at the same time or grown in mostly separate seasons, just overlapping at some point. You can even extend the concept to plants that are not grown together at any point in their life cycle, but follow one another in the garden bed.
This post is about why you should consider companion planting, along with some examples of good combinations. Similarly to the Planting Seeds: Inside or Outside post, it's to give you an understanding of it so that I can mention it in the individual plant posts with a brief reason and then move on.
What are the benefits of companion planting?
Efficient use of space
Plants with big roots, like tomatoes, need to be planted quite far apart for optimal growth, as the roots can spread quite far. Plants with smaller roots, like basil, can be planted in gaps between the bigger crops to use that space. The amount of smaller plants you can fit in is going to vary, but even 1 smaller rooted plant in between can save space and allow you to grow more.
Provide shade
Planting bigger plants next to others can provide them with shade. Some plants like the shade or want to be shaded during the hottest part of the day in summer, such as lettuce and spinach, which will often bolt in the heat, going to seed and slowing the production of leaves. The leaves of some species will go bitter when they bolt too, so unless you are trying to grow them to save seeds, bolting is something you'll want to try and avoid if you can.
Provide growing support
Tall, strong stemmed plants like corn or sunflower can provide a growing support for climbing plants like beans or squashes, whereas the alternative is to grow them up cane supports. There's an ancient method called the Three Sisters, used by Native American tribes, where the squash plants on the ground shade the soil and provide weed suppression, and the corn grows tall, providing a climbing support for the beans. Support can also be offered by protecting from wind, or even somewhere for the plant to lean so that its weight can be supported and it doesn't snap.
Attracting beneficial insects
Nearby flowers can attract pollinators. Fruits are formed from flowers that have been pollinated, and while some are wind pollinated, others need insects to do this for them, or are more reliably pollinated by insects rather than the wind. You can hand pollinate, but it can be hard and time consuming to do so.
Protection from pests
Scent is one way that insects can find plants, so hiding crops by masking the scent of other crops can make them harder for pests to find, or strong smelling plants used to deter the pests.
Some insects will eat common pests, like aphids. You can attract these predatory insects to your plants, or the area they are in, and hopefully they will reduce your pest problem.
There are some crops that pests prefer. You can plant some sacrificial crops, called 'trap crops' that should attract pests as they are a preferred plant over the one you are trying to protect. It's a bonus if you can compliment that with attracting predators. You may also be able to harvest something from the trap crop at the end of the season, or get some nice flowers from it during the growing season.
Improve flavour
Some crops improve the flavour of other crops when planted nearby. This is supposedly the case for improving the flavour of tomatoes by planting basil next to them.
Provide nutrients
Planting legumes, which can add nitrogen to the soil, next to a plant that's a heavy nitrogen feeder can provide it with additional nutrients during the growing season, leading to better growth.
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| A beautiful nasturtium flower |
Marigolds and tomatoes. Marigolds can help deter whiteflies and aphids, while also attracting pollinators.
Marigolds and beans. Marigolds can deter pests, attract insect predators for the pests, and attract pollinators.
Borage and strawberries. Borage attracts pollinators and insect predators for pests, and is also said to improve the growth and taste of strawberries. While it isn't native, borage is naturalised to the UK and not deemed invasive. And you can cut the head off before seeding if you want to be extra safe.
Lavender and carrots/leeks. The strong scent can repel or 'confuse' pests, as well as attracting pollinators to the area (which aren't useful for the carrots or leeks unless you are allowing them to go to seed, but can benefit the garden in general). Lavender is perennial, meaning it lives for more than two years, so its placement in your garden will be permanent or semi-permanent, unless you grow it in pots and move it around the garden or transplant it.
Nasturtiums can be a companion to many plants, including those in the brassica and nightshade families. They can repel pests, draw others away from plants, and attract pollinators.
There are a lot more pairs that you can grow together, and I will recommend some in the individual plant posts, along with the benefit that they can provide.
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| A Marigold flower in the garden amongst the crops. |
Plants to avoid growing together
While there are many plants that do well when grown together, there are plants you want to avoid growing too close to each other. This is sort of a different topic, but I think it fits within this well enough to put them together, and it makes sense to mention those to avoid growing together at the same time as I'm recommending plants to grow together.
Alliums and legumes. Plants in the onion family can stunt the growth of legumes if grown too close.
Brassicas and strawberries/tomatoes. They compete for nutrients and moisture, and strawberry growth can be inhibited.
And many more.
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