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TROPO's Organic Info Library

Good companions

A collection of ideas and information compiled by Graeme Eggins

For centuries companion planting has been a popular technique to combat pests and diseases in fruit and vegetables in Europe. In Australia. the upsurge of public demand for organically grown crops and corresponding move away from using chemical pesticides and fungicides is seeing a renewed grower interest in studying the compatibility of plants.

In a field trial at the Gatton Research Station, two Queensland Department of primary industry horticulturists reportedly proved the effectiveness of using dill to control cabbage moth in broccoli.

A row of dill was planted to every 15 rows of broccoli in an experimental block, which was also treated with the bacterial insecticide Dipel. The cabbage moth lay was a third of that in a block of broccoli treated conventionally.

This trial followed successful companion planting trials using thyme and rosemary run by the Victorian Department of Agriculture

Until very recently, companion planting appeared to have attracted little scientific research,.possibly because it covers so many aspects. A plant may prove an excellent companion to another because it excretes a substance from its roots or leaves, attracts or repels specific insects by its smell, breaks up the soil, draws up trace elements from deep underground or offers shade or shelter.

A glance over the shelves at libraries and bookshops will show that there is no shortage of advice and guidance for home gardeners. New books come out every year listing what plants grow best with what others and what combinations to avoid.

However, much of the printed information is based on experiences in temperate gardens, specially in Britain, and thus has only limited application to sub-tropical areas such as the Richmond/Tweed. (How many local growers want to know that foxgloves are great with apple trees?)

Even the published American research has been largely confined to the cooler States of the Union. Also, very little information is known about trials of companion planting on a commercial scale. However, as recent reports indicate, all this is changing. both here and overseas.

A number of North Coast growers are experimenting with both herbs or other plants to see if`they can find new beneficial relationships.

Editor's note: This article originally mentioned Equisetum (commonly known as horsetail) as a possible companion plant, but Equisetum is a declared noxious weed in NSW and other states of Australia. Don't plant it, and do report it to NSW Agriculture if you find it anywhere in the Tweed Richmond area. It could cause significant environmental and economic problems, is toxic to stock, etc. For more info please see the comment at the end of this article.

Lemon grass, which originated in South East Asia, is increasingly grown as an inter-row crop in orchards. Not only can it he harvested and sold as a herb (fresh or dried) but it makes an excellent Mulch.

Lemon grass is also grown in closely planted rows to form a living barrier against intrusive ground covers such as kikuyu.

Another popular herb, comfrey, is grown as a living mulch around or close by many vegetable gardens. The hairy comfrey leaves contain valuable trace elements and minerals which have been brought up to the surface by its deep-delving roots.

Comfrey leaves left to soak in fresh water for a fortnight or so make an good fertilizer Fresh, it is recommended as an excellent addition to the diet of cattle and is reputed to help strengthen the legs of horses. specially those bred for racing. Comfrey can also act as a very effective fire barrier if planted around the foundations of buildings or the verges of gardens.

Marigolds are deservedly popular and successlul companion plants and the Tagetes variety grow very well in the sub-tropics. In fact, if positioned too closely to other plants, they can almost overwhelm them. They are also likely to self-seed wildly, which is not necessarily a bad thing, depending on the situation.

The herbs tansy, basil. garlic, pyrethrum and southernwood have all been tried in North Coast orchards in an attempt to keep fruit fly at bay. However, while possibly helpful, they do not prevent fruit fly damage.

An occasional clump of horseradish in a shady part of the orchard has been found to help combat fungus problems.

Virtually all the common herbs are considered beneficial to North Coast orchards and gardens. They help attract bees and other beneficial insects while sprays made from the likes of.chives, garlic. hyssop, chamomile, horsetail and elder can be used to combat fungus, mildews and some pests.

Incidentally, elders grow like wildfire on most Northern Rivers properties and should never be planted where they cannot be controlled. Also take care not to drop any prunings - they will take root almost before your eyes!

Another plant which has proved particularly suited to cultivation in the Australian sub-tropics although no one boasts of it - is hemp (also known as marijuana) which can be used as an effective companion plant for vegetables including potatoes. However, don't expect the police to believe that!

To quote the·Encyclopedia of Gardening, published in England in 1824 by J.C. Loudon: "If in a patch of ground where cabbages are to be planted some hemp seeds be sown all around the edge in the spring, the strong smell which that plant gives in vapour, will prevent the butterfly from infesting the cabbages. The Russian peasantry, in those provinces where hemp is cultivated, have their cabbages within those fields by which they are free of caterpillars."

Seriously, some experimenters suggest planting winter-flowering herbs to attract predators of pests early. They are then in position ready to deal with pests that hatch out or migrate in spring. Garlic, pennyroyal and tansy are all suitable companions to orchard crops.

Not all organic gardeners believe in companion planting. Queensland author Jeff Hedges wrote in Harvesting the Suburbs published in 1985 that he had reservations:

"Certainty, sometimes a certain crop doesn't do very well ... but that's my fault for not "tuning in" properly, not the fault of the plants next door! If I plant some crop in a particular spot and it doesn't do well, it means that I didn't select the appropriate crop for that particular place at that particular time."

Local TAFE organics lecturer Dave Forrest has suggested that although companion planting can be used with effect in a home garden, farmers found many find difficulty extending it to broadacre use.

Of course, not all good growing companions are plants. Small animals and birds are proven colleagues for organic growers.

For example, a local Permaculture teacher suggests basing a guinea pig at the base of every fruit tree - it needs to have a weatherproof hutch.

These rodents, Whose territorial limit only extends about 4m from the tree, will keep the grass shorn short. They also attract pythons who in turn will hopefully - eat rats if they can't catch the little guinea pigs.

While guinea pigs may not be practical except in the small home orchard, poultry such as geese and chickens have proved useful in larger establishments: Of all chickens bantams are the best attackers of insects and don't scratch up the soil as much as larger breeds. They also provide good eating and nice, if small, eggs.

Ducks and geese have been used for centuries in orchards, usually being let in for limited periods, normally in autumn and spring. They were also once widely used in the southern states of the USA to weed cotton and similar large crops. Today a number of orchardists in the Richmond Tweed area are using geese as sustainable mowers.

If you have any experience with successful companions, specially with subtropical crops, and you are willing to share your knowledge please drop a note to TROPO at P.O.Box 5076, East Lismore 2480.

Readers' Comments

Regarding Equisetum species made reference to in the good companions article. All Equisetum species are declared W1 noxious weeds in NSW and other states. They must not be planted, sold and if found notified to the authorities for immediate control. Equisetum is a weed of horticulture, crops and pasture situations. It also has the potential to be an environmental weed in riparian and bushland situations. The weed is extremely hard to kill due to its extensive underground root system. It is toxic to horses, cattle and sheep. NSW Agriculture would encourage TROPO to promote an alternative non weedy species rather than Equisetum. Any one that has Equisetum should report it to myself or to the Far North Coast Weeds Council.

Contributed by Rod Ensbey, Regional Weed Control Coordinator NSW Agriculture Grafton rod.ensbey@agric.nsw.gov.au on August 6, 2001.

If you have some relevant experience, please send us your comments to be added to this page.

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