Monday, July 16, 2012

Tidal Beds

Low Tide

Back in March, I briefly referenced sunken garden beds, and just the other day I railed against the false wisdom of raised beds. The more I think about it, the more it seems like the garden wisdom takes a while to play out, and favors an oscillation, an ebb and flow, rather than zealous favoring of one level or another.

If you read the raised bed rant, you may have figured out that many of the problems stem from inflexibility: the unchanging, unyielding perimeter with a static elevation. Horizontal extent of a garden bed may be constrained by your available space, but still the bed (or at least the weeded portion thereof) should be able to grow over the summer, and perhaps retreat during winter.

Rising Tide
You can play around with elevation a lot more, though. Some plants like to be in mounds to begin with. You've heard of a 'hill of beans," right? My cukes start out in ringed hills worthy of Celtic chieftans. Then of course there are the potatoes and other plants that benefit from having more and more soil piled up around them as the season progresses. Meanwhile, blueberries and mints like the low wet ground, sopping up whatever water runs from the hills. Within a given bed, highs and lows occur across space and through time.

This attitude is especially well suited to my local soil, which is a fairly sandy loam borne of glacial retreat. It's easy to work. I dig out lawn and sculpt to the levels I want. Or give the bed a tilt. Banking a bed high to the north and low to the south creates a small advantage to crops in northern climes, bringing the ground a bit closer to perpendicular to the lines of photons coming from the sun, fooling seeds and starts into thinking they're a few weeks closer to summer. The same aspect that makes Washington's Columbia wines more famous than Oregon's--a southerly slope to the river--can be replicated on a small scale in my yard with just a shovel and garden rake.

The plants themselves add to the effect, and so planning is important. Put the raspberries and pole beans to the north, and work your way down to the ground-huggers at the south. A big plant at the south snags the photons, relegating anything north to a dank dark pit. Fine if you want ginseng and miners lettuce, but not so good for your garden variety plants. Knowing how early and how fast things grow matters, too; you can plant greens that rise early or late in the shadow of a mid-summer monster, since the don't much care for solstitial high noons anyway. Knowing when and how quickly each plant will grow and fade allows a gardener to overlap to a degree, getting more out of every inch of garden space.

Any one variety of plant ebbs and flows, and likes to be high and drained or low and sodden. Your whole bed may start small and grow over summer, flooding south, toward that that photosynthetic sunbilical, only to retreat again. I use this knowledge to be a little lazier, dispensing first with those heavy, labor intensive (and pestiferous, don't forget) walls. I may be still digging bigger well after the solstice if some plant or transplant could use the ground; no need to cram a Summer's worth of work in March. Go with the flow.

And don't fight the flow. Why would you want boards or bricks or railroad ties blocking your garden's roots? A single-level bed works fine for a monoculture, but not much more. Roto-tilling a big bed for a few tiny starts and seeds invites a flood of weeds. A rectangle of introduced 'soil' intensively cultivated, watered, and fertilized year after year is great, if your aim is to create pest habitat.

Summer's tide pulls high only once a year. Long northern days feed photons aplenty to the plants that ride this one big wave. Growth crests, and drops off when the clouds show up or the days just get too short. It's a good ride, and sooner than you'd like you slide into Winter, where there's time to reflect and maybe even think ahead.

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