Backyard Permaculture: Stacking Functions vs. Companion Planting July 14, 2013 17:07
When people first encounter Permaculture, they often get the impression that it refers to off-grid homestead sites of 40 acres or more. While many Permaculture design consultants do work with such sites (think eco-villages), it doesn't mean that Permaculture principles aren't useful on much smaller scales. In fact, due to the micro-scale of many urban lots and the sun/shade constraints posed by ever-taller urban developments, urban gardeners stand to benefit from applying permaculture thinking probably more than their rural counterparts. In fact, many backyard gardeners are already utilizing permaculture principles to their advantage, without even knowing it! If you plant flowers to attract pollinators, you're doing permaculture! If you grow runner beans on poles or trellises instead of wasting valuable ground space, you're doing permaculture! If you're growing a grape vine on an arbor to provide shade to your patio, you're doing permaculture!
Whether you're conscious of it or not, if you choose to place elements in your garden where they can provide more than just a single crop, you're applying the permaculture principle of stacking functions. By placing mutually beneficial species together, you'll get more out of your garden and with less work because nature will be working for you. And when I talk about the output of certain garden plants, I don't just mean the amount of edible fruit they produce. More broadly, output refers to all the services a garden plant may provide--like attracting pollinators and other beneficial insects, habitat for wildlife, privacy, shade, erosion control, enjoyment (of looks or scents), nutritional support for adjacent plants (nitrogen fixation), fibers, building materials, medicines, mulch materials, etc. Seasoned gardeners will surely be familiar with the concept of companion planting, in which certain plant pairs are deemed to be friendly (or not). For example, carrots supposedly love tomatoes, but do they really have a romantic attraction to tomatoes or do they simply prefer the cooler temperatures and more consistent moisture levels provided by the shade of the much larger tomato plant? Radishes, it is said, are particularly succulent when grown with lettuces. But, it isn't because of some magical connection between the two; the fact is that growing succulent radishes requires a consistently moist soil and the best way to keep soil moist is to keep it covered, for example with a "living mulch" of leafy lettuce plants.
In addition to stacking functions of moisture control, shade, and possible pest deterrence, alternating rows of low-growing leafy plants with root crops that have more open, upright leaves (like carrots, onions, or garlic) can save space in a small urban garden by using the same area to grow an above-ground and below-ground crop. Where companion planting is based on observation rather than folklore, I would say that it approximates a very simplified version of stacking functions but it overlooks a lot of valuable services that can be provided by plants. (Not that you shouldn't continue to plant marigolds around your tomatoes if that's been working for you!) At the gardening workshop this Thursday, we'll explore this valuable permaculture tool and talk about ways we can stack functions in our own backyard gardens. In particular, we'll look at the example of the Three Sisters--corn, squash and beans--which have been grown together for centuries by East Coast Aboriginal peoples. In brief, all three grow better (and with less work by the gardener) when combined than when grown separately. Corn and squash are both nitrogen heavy feeders, which the beans are able to help provide by fixing atmospheric nitrogen. The corn returns the favor by acting as a pole for the beans to climb; the squash serves both the corn and the beans by covering the ground with its broad leaves, thereby suppressing weeds and controlling evaporation.
What do you do if you don't have room to grow a stand of corn? What if you don't like beans? Come to the workshop Thursday to find out how you can apply the concept of stacking functions to your own plantings, even if all you're working with is a few planters on a balcony!