Modern gardening techniques in many countries typically involve filling garden beds with only one type of plant (monoculture). This is seen more with edible plants, however some people plant monocultures of ornamental plants too. Monocultures make it easy for pests to find their favourite foods, make it easy for diseases to spread and also cause depletion of soil nutrients, which in turn weakens plants and makes them more susceptible to pest and disease attacks. Companion planting is the practice of planting different plants together (polyculture). It is a great, natural and cost effective way to prevent the depletion of nutrients from your soil, which helps your plants cope with and repel pest and disease attacks. It has other benefits too though.
There are certain types of plants that are particularly good companions for certain plants or plants from certain plant families, but there are other general companion planting principles that you can use in your garden to:
- repel pests
- hide plants
- repel weeds
You can also use companion plants to attract insects, birds and other fauna that help to control your pests by eating them or killing them in other ways. Insects that aid your garden in this way are called beneficial insects.
One of the best ways to attract beneficial insects is to plant a range of flowering plants. In particular, it's a good idea to choose plants so that you can have a year round display of flowers, or as close to a year round display as possible (in very cold climates, you might struggle to find hardy plants that will flower in winter but luckily, pest insects aren't generally active when it's that cold either). That way, you can attract beneficial insects all year, not just when your favourite plants are flowering. If you're interested in attracting specific beneficial insects, this companion planting book has a chapter dedicated to specific plants that attract specific beneficial insects. You can attract birds to your garden by companion planting spiky bushes that provide shelter for small birds and choosing plants that produce lots of seeds and/or nectar. Choosing plants that are native to your local area, will help you to encourage native birds. They're also a good choice because they should be well suited to your local conditions. Birds will also appreciate a bird bath or pond that contains a reliable source of water for them.
Beneficial insects and birds will never completely eradicate pest insects. This is a good thing because otherwise, there wouldn't be enough food for them so they would stop coming to your garden and then pests would move in again and become a problem once more. This means that gardeners need a way to protect their plants from the remaining insect pests. One good way to do this is to companion plant with aromatic plants. Such plants can repel pests, keeping them away from your garden beds. They also mask the scent of the plants that you wish to protect, hiding them from insect pests that use their sense of smell to find their food. This is a powerful way to protect your plants from insect pests.
Using companion plants as a border is an effective way of preventing weeds from creeping into your garden beds. Lucerne and barley are two particularly effective plants that can be used to create weed borders around your garden beds. Some plants also produce special chemicals that can inhibit the growth of other plants. Sunflowers for example, produce chemicals that inhibit the growth of most grass weeds. By choosing such plants as companions in your garden beds, you can drastically reduce the amount of time you spend weeding. If you'd like to know more about using companion plants control weed problems this companion planting book contains chapters on companion plants that can be used to inhibit weeds. It also contains lists of plants that can be used to repel pests or mask the scents of a variety of plants.
The most important thing to remember when practicing companion planting is that all garden beds, whether they are for ornamentals or edibles, should contain a variety of plants, especially plants from different plant families. This will drastically improve soil health by preventing nutrient deficiencies and also by preventing the spread of soil borne diseases. There are a variety of other ways that companion plants can help you in your garden. Find out more by reading this comprehensive guide to companion planting.
Examples of Effective Companion Plants
Rosemary is one of my favourite companion plants to use in any area of the garden. Being perennial it is best placed either in a border or in the centre of a bed. Prostrate rosemary is fantastic hanging over the walls of raised garden beds.
Being aromatic, it deters a wide range of pests, but is still pleasant to the human nose. It's also great in the kitchen. Cuttings of rosemary can also be spread around the garden and they're particularly useful for deterring snails from tender young seedlings.
Rosemary is also good at disguising the smells of commonly attacked plants so that pests find it more difficult to find their favourite meals.
Rosemary is particularly good as a companion to carrots as it is a good deterrent for carrot fly. It should not however, be planted near potatoes. If you want to plant potatoes in a bed with rosemary in it, put a barrier plant in between the two.
Chamomile has both antifungal and antibacterial properties. As a companion plant, it can thus protect nearby plants from infection. It is also a beneficial companion plant in any area of the garden because you can make a 'tea' using the leaves and/or flowers that can be sprayed on plants that are susceptible to both fungal and bacterial diseases in order to prevent infections. This tea can also help treat such infections.
In addition to these properties, chamomile flowers attract pollinators and beneficial insects - they also make a lovely calming, antiseptic (drinkable) tea. Chamomile also makes a lovely ground cover that can be used instead of grass - particularly between garden beds.