Down in the Garden: How Companion Planting Works

Polyculture is the practice of planting combinations of plants for stronger, healthier growth and greater yields in productive agriculture.

When we think of companion planting, often it is considered as simply a form of controlling pests by adding plants to our gardens that certain insects don’t like.

This is a part of the equation.

Companion planting however, not only controls pests, it will inhibit the growth of unwanted weeds and improve the fertility of the soil.

Let’s look at the various benefits of companion planting for pest control, soil health and thriving plants in your garden.


These are a few pests you might encounter in your garden and some of the plants that can either confuse or repel them along with tips for attracting their predators.

Bugs in General

A border of chamomile, a hedge of feverfew or plantings of millet will deter most insect pests.

We cannot forget pyrethrum as it is a very strong pest deterrent.

Another clever way to combat insect invasions is to try planting more native shrubs as these will attract native birds that will in turn eat the bugs.


Pest control plants are tansy, pennyroyal and spearmint.


Marigolds, chives, garlic, onion, wormwood, coriander, rhubarb and elder repel these.

Cabbage Moth

Tomato and peppermint confuse and repel cabbage moths.

Other moths can be deterred with rosemary and santolina.


Mustard, marigolds and lavender send nematodes on their way.

Stink Bugs

Artichoke and radish are very disliked by these bugs.

Slugs and Snails

Rosemary, wormwood and mullein all deters them while mulches of these and oak leaf mulch are also effective.

Birds eat snails and slugs so plant bird attracting plants like buddleia, banksia and grevillea will bring them into your garden for some extra protein.


Alyssum, chamomile, pennyroyal, thyme and basil will control thrips.

Sunflowers, dill, coriander, tansy, yarrow, alfalfa also attract thrip predators.


Feverfew, garlic, marigolds, nasturtiums and basil can control whitefly.


Inviting what may seem like pests into the garden can sound strange but in fact there are many beneficial bugs that can help you grow a great garden.

Lay down the green carpet welcome by planting lots of flowers to attract pollinators to help fertilise your plants.

Consider letting some herbs and greens go to flower as well as planting specific flowers such as dahlias, forget-me-nots, sunflowers, roses or daisies.

There are also flowers that naturally attract insects that are predators of destructive garden pests. Ladybirds are going to take care of the mites, scale, whiteflies and aphids for you and they really enjoy dill and coriander.

Lacewings will make a meal out of aphids and they also enjoy tansy, angelica and dandelions.


To fix nitrogen to the soil for plants that require it, try planting sweet pea, alfalfa, nettle, soybean and clover as companions.

For soil low in magnesium plant in peppermint and parsley and let those dandelions roam free.

If your root crops are not much chop, try planting in garlic, sorrel, calendula, nettle amongst them as these all add phosphorus which could be your problem.

To ensure tasty fruits and vegetables, you need potassium in your soil to improve the uptake of nitrogen so get in some evening primrose, sunflowers, watercress, tansy and borage.

Control weeds by planting comfrey.

This acts as a living thick mulch and can be slashed down and added to your compost for a rich boost in nutrients.

Create well-planted boarders to stop grasses invading your garden beds and use these areas to add pest deterring plants such as pyrethrum and daisies.

Living mulches are simply plants that grow to cover the soil to trap in the nutrients and deter weeds so consider comfrey and other herbs that have the qualities your particular garden requires.


There are many great companions in the plant world – I have set out some in the adjacent box.

If I had to share with you my favourite companion plants, I could not go past marjoram for its ability to boost the flavour of nearly all surrounding crops while providing nutritional assistance to the environment it finds itself in and this is turn produces very healthy plants.

My other favourite is comfrey for its ability to become a living mulch that deters pests and weeds, provides temperate regulation and water retention and it also creates an amazing liquid fertiliser.


Some plants do better in the company of friends.

These botanical mates offer nurturing through their ability to share nutrients with others; by attracting insect predators, usually through aroma or taste, and by adding something to their neighbours in the way of additional flavours or boosting their growth rate.

Here are a few combinations for you to try that should improve your garden.

Artichoke, Jerusalem (Helianthus tuberosus): they love being with tansy and corn and will deter insects from your citrus trees if used as their underplanting.

Asparagus (Asparagus officinalis): brilliant bedfellows are tomatoes and asparagus as they naturally stimulate healthy, strong growth in each other.

Parsley, capsicum and lettuce all do well with asparagus too.

Bay Tree (Laurus nobilis): one of the great pest and disease deterrents for all other plants and should be found at least once in every garden.

Beans, Broad (Vicia faba): lettuce, corn, violets, potatoes are all good neighbours.

Beans, Runner (Phaseolus coccineus): This type of bean loves growing alongside carrots and cauliflowers and does well with spinach, radish and corn.

Broccoli (Brassica oleracea): this vegetable loves growing with rosemary, leeks, celery and sage.

Celery (Apium graveolens): leeks, tomatoes and especially bush bean varieties work very well together with celery in the garden.

Citrus (Citrus spp.): sweet pea grown alongside citrus of all types will help fix the nitrogen in the soil and to deter woodborers plant catnip and lavender beneath your citrus.

Cucumber (Cucumis sativus): To encourage stronger growth, try planting peas and beans and you will find that lettuce makes a healthy garden bed companion as well. The dreaded cucumber beetle can be deterred with radish that has been allowed to go to seed.

Lettuce (Lactuca sativa): To improve the flavour of your lettuce, try planting between rows with beetroot or strawberries.

Mulberry (Morus alba): To ensure a bumper crop of mulberries, plant grapes and chokos nearby – you can grow either through the branches as well.

Olive (Olea europaea): Rosemary, lavender and tansy all make a good underplanting for this tree as they repeal many pests that are attracted to it. Wattle is a brilliant native companion and almond and walnut also help create a beneficial growing environment.

Onion (Allium cepa): Onions do well with lettuce, cabbages and carrots and you will find that chamomile is also happy growing aside onions.

Passionfruit (Passiflora spp.): Lemongrass and lemon balm are both good pest deflectors and marjoram is an extremely beneficial nutrient provider.

Pumpkin (Cucurbita spp.): They grow well around citrus, beans and corn while dill and oregano are good pest controllers.

Rose (Rosa spp.): There is belief that growing alliums such as chives, onions and garlic with roses will improve the perfume of the rose. Chamomile helps prevent the development of black spot and parsley will deter pests.

Strawberry (Fragaria x ananassa): Borage improves the sweetness of strawberries while marigolds deter pests.

Sunflowers (Helianthus annuus): These big beautiful blossoms will lure aphids away from the rest of your garden without much harm to themselves and are massive pollinator attractors as well.

There are also some plants that do not make good bedfellows.

Some emit substances that harm certain neighbouring plants, many attract plant predators that are unwanted, while others deplete available resources that more fragile plants can’t compete with.

Tomato, for instance, do not do well with fennel, potatoes or kohlrabi and strawberries find it difficult to grow around collards.

Don’t ever plant Gladiolus in with your vegetables as they are nutrient thieves and your crops will be stunted in growth.

Sunflowers and potatoes or beans will starve each other out.

Alliums are your onions, garlics, leeks and chives and they do not make good neighbours with beans, peas or asparagus.

Beetroot and amaranth don’t seem to mix with each other, potatoes and artichokes are not friends at all and all of the brassica family (such as: broccoli, Asian greens, cabbages, cauliflower) should never be grown near the nightshade family (such as: tomatoes, potatoes, eggplant, capsicum) or strawberries and rue.


Herbal Tea Workshop: Includes plants and tuition on growing and making your own herbal teas. Coachwood Nursery Somersby. 4pm to 6pm 28th November. $49 Bookings: 0491147448

Christmas Twilight Shopping from 5pm Thursday 5th November Burbank House and Garden, 443 The Entrance Road, Erina Heights.

Garlic Plait and Wreath Workshop: Create these beautiful festive gifts for the foodie in your life. Bumble Hill Shed Shop, Kulnura. 11am, 5th December. Bookings: 04256834459

Cheralyn Darcey is a gardening author, community garden coordinator and along with Pete Little, hosts ‘The Gardening Gang’ 8 – 9am every Saturday on Coast FM.

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