So, call me the sceptical permaculturist if you want, but after my rant about mulch, today I'm going to go after companion planting. Not against the principle itself, which is great, but more on the subject of the over-optimistic and simplistic way with which the concept is sometimes approached. At times, I have myself enthusiastically and at length described the benefits of companion planting and how if you plant this plant with that plant you'll not only have an awesome trouble-free garden but you'll also save the world, and you won't even need a revolution! Hurray!
But then when you get down to it, all these pesky questions come up. How close does the borage need to be to the tomatoes in order to improve their growth and flavor? How far apart can you plant patches of calendula and still get their pest-repelling properties? How much marigolds do you need to make any difference to the nematodes? Basically, once you know what plants go together, the question becomes how do you plant them?
One thing I found really interesting while skimming through one of the myriad organic gardening books in a bookstore was that the effect of companion plants varies greatly depending on the circumstances. In "Jardiner Durablement", Jean-Michel Groult gives the example of sage, a companion to cabbage (it repels cabbage butterflies, supposedly). It grows best in a hot, well drained soil, but will give off almost no volatile chemical compounds in these circumstances, whereas it will do so more readily in moist soil, though it might not grow as well. This was really interesting to me, and it makes a lot of sense. The quality of the soil, air and soil humidity, soil pH, nutrient content and so on will all affect a plant's growth and therefore its quality as a companion.
You can start reading up on this subject and just never get to the end of it. But ultimately, I think the best advice is that of Jon Jeavons in "How To Grow More Vegetables": it's up to each gardener to try out combinations of plants and find out which ones work well in the specific context of each garden. He advises to start with combinations of few plants (only 2 or 3), in order to be able to really figure out what's going on.
I think this kind of experimentation is really very valuable, because you can't really rely on lists of companion planting combinations without testing them (and generally the planting details to make these combinations work are not mentioned). And then again sometimes you'll find that some unusual combinations will work in your particular context. In a broadcast bed we threw some peppergrass seeds and some alfalfa (among other things). The peppergrass started growing in patches where the seeds had fallen, and later the alfalfa started growing through the peppergrass. What I think happened here was that since we gave little care and little watering to this bed, the alfalfa seeds only sprouted successfully under the protective cover of the peppergrass, and the patches of bare ground where no peppergrass seed had fallen remained barren of alfalfa also. Who would have thought? Of course, to replicate this kind of thing with other plants you would really need to know the plants' growing habits well. This is the kind of thing you can only figure out by trying combinations of plants in the garden.
Has anyone out there done any interesting experiments? What combinations of plants have you found to work well in your garden?
4 comments:
In my opinion this is a little like discussing vitamins vs healthy eating. In other words, you can just eat a balanced diet with a variety of foods and not worry about anything else, or you can look at all the vitamins your food contains and worry about getting enough of each one.
It's not that you shouldn't consider you might be missing something in your diet if you get sick, but most people don't need to worry about the vitamins.
It's a little the same with companion planting vs general biodiversity.
If you're a farmer you probably specialize in a small number of crops, maybe even only one. When you grow large monocultures, you end up having very specific problems. If you do the same thing in your garden, you can have similar problems. This is why if you grow annuals, you should plan sensible rotations (and perhaps companion planting), and if you grow perennials you should think about companion planting and in general maintaining as much overall biodiversity as possible.
I tend to look more carefully towards companion planting for two reasons. First to plan rotations, specifically to know what plants are enemies and can't be grown near one another. The other is to address specific problems in my garden.
In my case I sometimes have problems with a lack of nitrogen, so I tend to use a lot of nitrogen fixing plants as companion plants. Over time however the nitrogen levels in my garden are increasing, so this is less of a concern.
As other problems come up, I'll certainly look further into this. This is how the Internet is great!
The image of the vitamins vs. a healthy diet is a great one! It's true that you don't need to worry about understanding exactly all of the plant interactions in the garden, but I guess that even with a healthy diet you might want to know how your body processes food.
I'm with you - companion planting is so confusing! My first year gardening I found coriander worked great to keep the aphids off my salad levaes - the second year, aphids ate the coriander. Go figure.
One thing I have found REALLY works though is growing petunias under asparagus. The first year my asparagus plants were absolutely overrun with asparagus beetles. I planted some petunias there in late summer - too late to save them really - but the next year... not a single asparagus beetle. I do it every year now and have not seen another beetle on my plants since!
Love the blog!
I'm really interested to find out more about companion planting too and have been experimenting over the last couple of years. Best so far is chamomile grown with brassicas to keep whitefly away - definitely looks to be keeping populations down - and I get chamomile tea out of it too! I've posted a photo up on my blog here: http://oakhousepermaculture.blogspot.com/2010/05/first-year-in-review.html
And yeah, I agree with Nome - really nice blog you've got going here!
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