What is companion planting?
Companion planting is the concept of growing different plant species together so that the plants benefit from each other. Companion planting increases biodiversity in the garden and can assist with pest control, pollination, and nutrient uptake thereby increasing crop productivity. Companion planting can help to foster a balanced ecosystem in your garden. Planting a mixture of different herbs and flowers in the vegetable garden, will help to attract a variety of insects, birds, bacteria, fungi, and earthworms which can all benefit a healthy organic garden.
However, plants have their likes and dislikes and grow strongly or not depending on the company they keep. This is known as ‘allelopathy’ which refers to a negative or positive effect on one type of plant, by a chemical produced by another type of plant. As such, it’s important to make sure plants are compatible before planting them next to one another. You also need to avoid choosing plants that have competing root systems and ensure that there is enough room for plants to grow.
Benefits of companion planting
There are several benefits to companion planting. A companion plant may repel pests, attract beneficial insects, benefit the growth of another plant, improve the soil, and increase harvest yield. By improving soil quality through companion planting, you can also reduce the risk of diseases caused through nutrient imbalances, help with moisture retention, and reduce weed growth.
Herbs make great companion plants. Not only are they good for our health, but they are an organic gardener’s greatest ally in deterring insect pests, attracting pollinators, conditioning the soil, aiding composting, and enhancing the flavour of some vegetables.
Companion plants that deter pests
Certain plants have a strong scent or secrete chemicals that can help deter garden pests. The following herbs can help to deter pests in the garden and in the home:
Tansy (Tanacetum vulgare) is an aromatic herb that has been used for centuries as an insect repellent. Tansy is said to be good to plant for cabbages, roses, berries, and fruit trees. It concentrates potassium in the soil and so can benefit the growth of nearby plants. It can also be used to activate compost heaps or made into a liquid fertiliser. Dried tansy can be used in the food cupboard to deter ants and in the clothes cupboard to drive out moths or prevent them from settling. Fresh leaves can be used in chicken coop nests for the control of ectoparasites or an extract of the leaves can be sprayed on the chooks.
Feverfew (Tanacetum parthenium) has a strong-smelling and bitter-tasting foliage that repels insects that come into contact with it. The white daisy-like flowers attract butterflies and bees. Feverfew can be used to make an insecticidal tea spray for the control of sap-sucking insects such as aphids, scale insects, spider mites, thrips, and whitefly. Make sure to spray in the evening when there are no bees around.
Chives (Allium schoenoprasum) are an excellent companion plant. Not only do the flowers attract pollinators and other beneficial insects, chives also help repel some unwanted insects in your garden. This is due to their strong onion-like scent that insects like carrot flies and aphids don’t like. Grow chives near roses (to prevent black spot and repel aphids), carrots (making them larger and sweeter) beet, and apple trees (preventing black spot). Chives should not be grown near legumes.
Companion plants that attract pollinators
Companion plants that attract pollinators such as bees, butterflies, and other beneficial insects help with plant pollination, increased yields, and an overall healthier ecosystem. Planting spring-flowering plants such as borage, strawberries, and lavender around the base of fruit trees will encourage more bees to the area which will help increase cross-pollination, and result in an increased fruit yield. However, make sure that your pollinator-friendly plants bloom at the same time as your fruit and veggie plants for this to work successfully. Some of the more popular herbs that can be planted in your garden to attract pollinators include:
Bergamot / Bee Balm (Monarda didyma) is a perennial growing to around 100 cm that bears beautiful pink-red flowers in summer that are very attractive to bees and other insects. It is also thought to be a good companion to tomato plants.
Lemon Balm (Melissa officinalis) is a perennial herb widely cultivated for its fragrant lemon-scented leaves. The growing plant is said to repel flies and ants, and bees are attracted to its small white flowers, so it makes a great companion plant for the vegetable garden.
Borage (Borago officinalis) is a well-known companion plant, with bright blue edible flowers which attract bees. Borage plants accumulates calcium, silica, and potassium and as such it is also a useful addition to a compost heap or can be used for mulching. It is said that strawberries grown near borage produce bigger and better tasting fruit.
Companion plants that attract predator insects
Predator insects such as ladybirds and hoverflies, are beneficial in the garden as they capture and eat aphids and other small pests directly. However, these beneficial predatory insects do not live on aphids alone and need other natural sources of food such as nectar and shelter to complete their life cycle. The flowers in the Apiaceae family (also known as the umbellifers) are inflorescences that contain hundreds of tiny flowers which have exposed nectar sources which are perfect for these beneficial insects. Planting the following umbelliferous plants will help attract predator insects to your garden:
Coriander (Coriandrum sativum) that is allowed to flower will attract predator insects and bees. Dill, chervil, and coriander grown with carrots and cabbage will protect them from predation. This annual grows best in autumn and spring.
Yarrow (Achillea millefolium) is a low-growing perennial with feathery leaves and heads of white-pink flowers. The flowers attract parasitic wasps and hover flies, which are beneficial predators.
Fennel (Foeniculum vulgare), with its large heads of yellow flowers in summer, attracts a variety of beneficial insects including ladybugs, parasitoid wasps, bees, and hoverflies. Aphids are said to find fennel exceptionally offensive and are strongly repelled by it.
