Companion Planting

What is Companion Planting?

Companion planting is the practice of planting two or more types of plants close together for some kind of benefit, such as the control of pests, increased health and vigour, resistance to disease, or higher yields. These are termed “good companions”.

Companion planting is also concerned with plants are detrimental to each other and must therefore be grown apart. These are termed “bad companions”.

How Does Companion Planting Work?

There are several means by which companion planting works:

Pests Repellent Properties

Some plants exude chemicals from their roots, leaves or flowers that suppress or repel pests and protect neighbouring plants.

Nitrogen Fixing

Plants of the Legume family, such as peas, beans, clover, lucerne, tagasaste (tree lucerne) and acacias (wattle trees) have root nodules which create a home for Rhizobium bacteria, and these bacteria can take nitrogen from the air and “fix” it into a form that the plant can use. This is a symbiotic relationship, as both the plant and the bacteria are benefited by this teamwork. The nitrogen that is fixed by legumes also benefits neighbouring plants

Pest Decoys (Trap Cropping)

A plant that is more attractive to pests can be planted nearby as a decoy. This creates a diversion to draw pests away from the main plants you are trying to protect.

Camouflage

Many pests identify their food sources through scent or the physical outline (shape) of the plant. Pests can be confused by planting companion plants which release scents which masks that of their neighbouring plants. Companion plants can also be interplanted amongst the crop plant to mask their shape, making them harder to locate, so that pests miss them altogether.

Stacking

In the permaculture principle of stacking, taller growing plants that need more sun can create supportive cover for lower growing understorey plants that need more shade, and these in turn can create a sheltered ground level for more delicate ground cover plants, which results in all the plants receiving the conditions that they need to grow optimally. The net effect is that more plants are growing in a given space, resulting in higher yields per area.

Nurse Cropping

A nurse crop generally is a crop of trees or shrubs whose height or dense-canopy protects more vulnerable plants during their development from frost, sun or wind.

Habitat for Beneficial Insects

Beneficial insects include pollinators such as bees, predators of pests such as ladybirds, lacewings, hover flies, praying mantids, spiders and predatory mites (OK, the last two are arthropods, not insects!) and parasites of pest such as wasps. Beneficial insects need companion plants which provide nectar as a food source, or a habitat for them to live in. As a simple example, in a corn field, which contains nothing but corn, you have an ideal place for pests that eat corn to live and feed, but nothing to support the “good bugs” that eat these pests, there is nowhere for these beneficial insects to live!

Biodiversity

Having a mix and variety of plants together creates a more resilient ecosystem if pests or adverse weather conditions weaken or wipe out a particular variety, or type, of plant. This provides a form of security that ensures that the whole ecosystem does not collapse because one type of plant is attacked or fails.

See the Companion Planting Table listing all the good and bad companion plants here

 
 
 

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7 Responses to Companion Planting

  1. Perry says:

    What would be a good resource for matching plants together?

    • Perry says:

      never mind found it right in front of my eyes.

      • Blackthorn says:

        No worries, the companion planting table on this site shows you which plants work well with each other and which ones don’t. Enjoy!

  2. Perry says:

    One more question. When planting companion plants, say for example tomatoes, parsley, and garlic, what should the spacing be on these.

    • Blackthorn says:

      Hi Perry,

      If you want to do it by measurement, just use the same spacing as you normally use for the plants. If the spacing for garlic is to plant them 10cm apart, then plant them this far from each other. If the spacing is 70cm for tomato plants, then each plant would stretch out 35cm in every direction to make a 70 cm circle. If you plant the gardlic about 10cm from where this imaginary 70 cm circles edge is, that’s fine. That’s the ‘by the book’ approach if you’re using planting tables or the instructions on the seed packets or seedling labels.

      In reality. you just use common sense to estimate how big plants get (assuming you already have grown these plants before and know how they grow), and plant them accordingly, ensuring they won’t shade each other out. Smaller plants can fit in the gaps between bigger ones (as long as they get enough light of course!) and it all comes together in a harmonious mix. I must point out, gardening gets easier with practise as you get to know the plants really well and understand their requirements and exactly how they behave.

      For example, Tomato plants need good air space between them to avoid fungal diseases, so spacing is important, while parsley can be packed quite densely as you see in garden parsley patches, with no trouble at all. Garlic has long thin leaves which don’t shade out plants and can be situated close to other plants without any issues.

      Regards

      • perry says:

        Thank you!

        I’m starting a small 4 x 4 sq ft garden to start out and I’m very interested in your ideas, as well as permaculture, as a whole. I plan on placing tomatoes in that box, with some companion plants to help out. Plus it will all be shaded by my giant stand of Southern Pecan trees!

  3. David says:

    Hi Blackthorn, for an easy to use companion planting database check out http://www.plantingpals.com I don’t think it’s as expansive as your table but it fills in some missing plants. Thanks!

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