Companion Planting

vegetable garden planning companion planting

A monoculture is susceptible to disease and pests.

Companion planting is a system of planting a number of different plants together, so that they benefit by from their close association.  Sometimes in agriculture we may see monoculture, an areas where there is a single crop or plant species.  Whether its a plantation, a field or a garden bed or even a row this makes it easier for disease to spread and pests to invade.

In nature its much more common to see a diversity of plants intermingled and growing together.  The plants thrive more from their association with other plants in a number of possible ways.  Companion planting grows a variety of plants together for some mutual benefit.

Unfortunately there is a lot of myth and misunderstanding about companion planting. Companion planting is often portrayed like a Hollywood romance, an instant attraction followed by happily ever after. A helpful rule to remember is that companion planting will help solve a problem ONLY if that problem exists.  The problems that need solving are dependent upon the local conditions, and so the effectiveness of companion planting will vary as much as the relevant local conditions vary.  The problems of Europe may be no-existent in the US., the pests of North America may be absent from Australia. The soil conditions of one neighbourhood may be completely different to those of the next village. The conditions of shade, competition and previous use may be completely different in one back yard to that next door.

Occasionally plants that benefit each other in one situation may have the opposite effect in another.

Companion Planting and Nutrition

vegetable garden planning companion planting

Companion Planting involves a diversity of plants in one bed

One way that some plants can support others is by providing some nutritional element that is needed.  Most commonly nitrogen fixing plants provide support for root crops and heavy feeders.  Deep rooted plants can absorb a variety of nutrients from deep down in the soil, and make them available to other plants when leaves die back or are added to compost.

Companion Planting and Pests

If a disease or pest is present in the local environment, whether that is country, region or garden bed companion planting may help.  Pests find their target plants in a number of ways the action of the companion plants needs is related to this process.

Pests and diseases in the soil will be affected by plants that releasing a chemical into the soil that kills or repel that pest.  Feeding insects may identify their host plants by scent, in which case a plant that produces a masking odour would be a good solution.  Other insects identify their food by sight, so disguising their shape with plants of a totally different silhouette will confuse the miniature munchers.

Attracting predators that eat your garden pests is another way that companion planting can benefit your veggie patch.  Alternatively luring pest away from your vegetables to an alternative planted as a “trap crop” can be a solution.  I have heard of weeds being used in orchards and vineyards for this purpose.

Companion Planting for other reasons

Other reasons for companion plating are to attract pollinators, create a micro-climate, or even just the convenience of having plants with similar water and nutritional requirements together.  Sometimes plating some crops together can even improve the flavour of crops on your plate.

Allopathy or Competition Between Plants

Some plants actually inhibit the growth of other plants by competing for the same resources, or by creating an incompatible environment such as a growth inhibitor or making the soil too rich for a particular plant.  Inhibiting the invasion of your vegetable plot by weeds and grass is advantageous, but inhibiting the growth of one vegetable by another is something you will want to avoid.

Companion Planting in Practice

Overall multiple plants grown together in the same garden bed can improve yields and crop quality.  Best results are obtained by developing your understanding of companion planting in your plot as your gardening experience grows.  Experimentation and record keeping will build knowledge, and that is one of the roles of this website.

How I assembled the soil for my raised beds

raised vegetable garden beds

Weeds and leaves heaped in the garden bed form the first layer

When it comes to actually filling the raised garden beds, sometimes the ideal gives way to other pressures.    Ideally I would build the raised bed frame then fill it with varied layers of nitrogen rich and carbon rich.  Sprinkle on activators such as blood and bone and add trace elements through rock dusts.  I would let it sit for several months and encourage the chooks to turn it mixing it more and adding a little extra chicken manure.

Because of the circumstances of my move I found myself building garden bed when we were already half way through spring.  I needed to build some beds fast, and get some veggies in if I was to have anything growing this summer.  I also had little spare cash after the expense of moving, so buying material in was mostly out of the question.

Adding layers of nitrogen and carbon materials

raised vegetable garden beds

The bed is half full before I line the walls with plastic.

I gathered what I had available, used straw, grass clipping, weeds, dried leaves, some rich top soil which also contained lots of tree bark (not ideal), kitchen scraps.  I layered and mixed it as well as possible, watering it as I went.  I did buy a coir block and added that to one of the beds.  It did take me some time to gather all this, I started collecting and layering the material before I had even built the frames, and the first bed got a considerable amount of rain during the process.

When a raised vegetable garden bed is made out of treated or unknown timber it is important to line it with plastic.  Otherwise the poison used to treat the timber will leach into the soil and be pick up by your vegetables.  But this can be a fiddly business, especially if there is any wind about.  I find it useful to have some material already in the bed to hold the plastic in place as I line the walls of the bed.

Adding a plastic lining for the walls.

raised vegetable garden beds

Plastic prevents chemicals used to treat timber from leaching into the soil.

Initially, whilst still constructing the walls I had heaped material in the centre. When I was ready to line the frame I spread it out and added straw, until it was about half way up the walls.  I pushed the straw back just far enough to line the walls with plastic, where possible I wrapped the plastic around the top piece of wood or anchored it behind a post.  In this way I was able to hold the plastic in place with one hand and push the straw back onto it with the other.  After that I added a layer of nitrogen rich grass clippings.

One handy trick if you wish to plant into a bed that is not ready is to make a hole, fill it with compost and plant your seedlings into that.  Similarly a layer of compost on the top to plant your seeds into works well.  It takes several weeks for the seeds to germinate and the roots to grow beyond the compost, by which stage the soil components have broken down further.  But I hadn’t been here long enough to have any compost.

Purchased vegetable garden soil as the top layer is my compromise.

There was only one option left if I was going to get anything growing this season.  I had to buy in some top soil.  Now I know that purchased “soil” is inferior quality, but vegetable soil is generally better than the top soil that they sell, which is usually full of household garbage.   One cubic meter of soil doesn’t go very far in raised garden beds, but if its only 20cm deep it should cover 5 square meters.

raised vegetable garden beds

Tuck the plastic in so that it doesn't become a home for slugs and snails. It looks much better too.

I bought some “vegetable garden soil” which turned out to be a mixture of cow manure, sand, composted bark and who knows what else.  The cow manure should help things along a bit.  As I moved it I discovered not only does it contain lumps of bark, but lots of stones as well.  I filled the top of the beds with this purchased soil.

The final touch was to hide the plastic that was showing at the top edges, not only is it unattractive, it will harbour slugs and snails which would come out at night and eat my precious seedlings.  My raised beds were complete.

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