Companion Planting : What REALLY Happens When Basil meets Tomato

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It was love at first sight - just like the books explained - the ones that tell you how parsnips hate celery, and celery like cabbages. He was tall, green and handsome, the perfect basil plant, and she was a blushing tomato, a country girl at heart.

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He swept her off her feet (well, shook her to the roots anyway) and they produced prolifically all season, and were buried in the same compost heap that winter. (Yes, I know that's not romantic but we do need a bit of realism here).

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Actually, if I had my way myths like 'basil loves tomato' would be composted too. 'Tomatoes love basil' is one of the great companion planting fallacies. Tomatoes grown here with basil don't do any better or any worse than those grown without it: but if you condemn poor old basil to live his life next to tomatoes he'll probably get black spot.

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There are a lot of companion planting myths around - like growing marigolds to repel nematodes. Marigolds can repel nematodes - they'll repel them away from the marigold roots, and right into the arms of the poor flowers or vegies you're trying to protect. Not that it matters much - the main pest species of nematodes in Australia don't care one way or another about marigolds (most of them can't stand mustard though - but that's another story).

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So many companion planting hints have been passed on from book to book, all based on European observations - whereas Australia has quite different pests and predators, and garden relationships - and the 'companion planting' that works overseas may not work here at all.

In fact it's often hard to tell whether companion planting works or not. Most people who practice companion planting are exceptional, caring gardeners. When their loving touch gets rid of pests, produces blooms that stun the neighbours or cabbages as large as watermelons, they praise companion planting.

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They should be singing their own praises instead.

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To know whether one plant really grows better or worse with another you need to have at least two similar plots - say one with tomatoes without basil, one with both tomatoes and basil, and maybe another with basil all on his lonesome. Take lots of notes: measure how long the seed takes to germinate, how fast the seedlings grow, when they fruit, how much and how often. Then compare each plot's performance - and do it all over again next year as well.

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Having said all that, I now have to praise companion planting. It's because of companion planting that I don't have to use pesticides any more (except to test one sometimes), rarely weed and hardly ever fertilise.

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This year, for example, I planted pansies with my onions. Onions are slow growing and are easily overcome by weeds - but the faster growing, spreading pansies kept the weeds down and insulated the soil around the onion bulbs. We got bigger onions - and for much less work. (The pansies were pretty too.)

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I've harvested the onions today, in fact, and weighed them - and in one square metre so thick with pansies that you'd never know there were onions there at all I gathered 23 kiloes of the fattest, sweetest, most delicious onions you have ever tasted. (I admit a bit of bias here - all gardeners are fanatic about their produce).

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The pansies are still flowering. I suspect the onions helped protect them from aphids and fungal problems - but I'll test that next year.

This to me is the essence of companion planting - designing a system where the plants do the work. You don't need long lists of what loves what, either - in most cases, you can simply work it out yourself.

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Fertilising with Companion Planting

Many plants 'fix' nitrogen from the air - or, more correctly, the bacteria associated with their roots do. You can use these plants as home grown fertiliser to feed your garden.

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We grow masses of perennial climbing sweet peas - those lovely pink and white ones that come up every year and flower through most of summer. In autumn I pull down their debris and use it to feed nearby trees or vegies. Try growing peas, beans, lupins, broad beans and other 'nitrogen' fixers, and using the old plants to fertilise others next door. If you can bear to slash them down as soon as they flower they'll be much richer in nutrients before they've put most of their effort into next year's seeds - the beans or peas etc.

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I also use the trimmings from our wattle trees as fertilizer/mulch. It's nitrogen rich, breaks down quickly into stunning black soil (worms adore it) - and a light prune keeps the wattles healthier and in better shape too.

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Other 'nitrogen fixers' include casuarinas, honey locusts, sweet peas, soy beans, clover, peanuts, kennedias, broom (use sterile varieties that don't spread), woad and tree lucerne. The latter makes a lovely street tree by the way - evergreen, heat, drought and frost tolerant, with masses of honey scented white flowers all spring. Tree lucerne can be kept severely pruned - and the prunings make some of the best mulch I know.

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Weeding with Companion Planting

Many plants suppress the growth of other plants, or inhibit the germination of their seeds. This makes sense when you think about it. A plant wants to make sure its own progeny survives - and will do its best to wipe out the competition. (Even barracking parents at children's sports are far less ruthless than their plant equivalents).

Every spring I let some of my radishes, as well as cabbages and other brassicas, go to seed. The flowering vegies suppress the growth of everything around them. Then I water the garden, pull them out and have a relatively weed free garden, already dug over by the deep roots ready for planting - and the old radishes and cabbages can rot down to become mulch later in the year.

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I use a thick barrier of marigolds to suppress any couch grass that thinks it's going to invade the garden beds, and a thick hedge of comfrey to keep out kikuyu. The comfrey dies down each winter, about the same time the kikuyu stops growing. I slash the comfrey too three or four times each summer for home grown (and wonderfully rich) mulch. Don't ever dig around comfrey - it spreads.

You need to be wary of some growth suppressors though. Sunflowers suppress the growth of most plants around them - wonderful for clearing up a weedy patch, but not so good if you want other plants clustered around their legs. I sometimes grow climbing beans up our sunflowers. The plants are never as tall or as prolific as those grown elsewhere, but they produce beans up to two weeks earlier - good for an early crop - and the sunflowers seem to do better with the beans.

 

Attracting Predators with Companion Planting

Predators - from birds to dragonflies to tiny wasps (not the great ugly European wasps but Australia's enormous range of smaller good guys) - can control all your pests for you. When we first came here we had every pest on the Southern Tablelands. Now we don't have any major pest problems at all. We've still got a few pests - but they're kept in check by an enormous number of predators.

 

As I write I can see a tiny warbler picking off mites from the kiwi fruit leaves and a blue wren gobbling aphids on the roses. I know there are hoverfly in the grevillea and their larvae must be eating something... and the yellow robins and pollistes wasps cleaned all our pear and cherry slug up too before I could even take a photo of them (one year I'll get the camera out in time - but at the moment our photo library just has some not very good shots of where the pests were before the predators started guzzling).

 

Many garden predators are blossom feeders, and it's their larvae that like to eat pests. Birds also adore blossom - either to eat directly (even nectar feeders may eat pests when they're nesting - or if there are a lot of pests about - birds are great opportunists- you should se the honeyeaters dart about after flying ants round here) but also birds feed on the insects that are attracted to blossom- and then they move ont your veg nearby and clean up the insects there too.

 

Every garden needs blossom all year round. The best for attracting birds and other predators are probably those with tubular flowers (my favourite is pineapple sage - sweet smelling leaves with briliant red flowers and clouds of tiny birds), or any of the prolific native flowerers like grevilleas - especially the grevilleas that flower most of the year, like 'Robyn Gordon'. After all, most predators are natives too. A word of warning about grevilleas - many people are allergic to them, especially the hybrids of G. banksii. Before buying a grevillea stroke a bit of it on the soft skin under your arm pit. If you come up in a rash avoid handling that particular grevillea.

 

Confusing Pests with Companion Planting

Pests recognise their food supply either by its shape or by its scent. Most of our gardens are like a supermarket for pests - they can wander up and down the neat, straight, weedless rows saying 'I'll have a bit of this and a whole lot of that.'

Confuse them. Don't plant straight rows of anything - mix up your plants so you don't have great blocks of any one shape or scent - plant flowers among the vegies and vegies among the flowers for a productive (and beautiful) pest deceiving garden.

After all, this is what companion planting is about - letting your garden do the work for you , while you sit back and enjoy the flowers and bounty.