Raised beds for garden plantings can be warranted

Sunday, June 2, 2002

Raised beds are all the rage in gardening these days, but don't revamp your ground just yet. Raised beds are a lot of work, so before you grab your shovel, stop to consider whether they really are necessary or beneficial.

First realize that we are talking about two things: raised and beds. You cannot have "raised" without beds, but you can have beds without their being raised.

Bed-planting, raised or flat, has much to commend it. Yields are higher because plants can be clustered closer together. The leafy blanket over the soil that results from close planting also shades out weeds and shields the soil from pelting rain and wide swings in temperature.

Raised beds, on the other hand, do have some problems. Mostly, they dry out too quickly. And the higher and narrower they are, the more quickly they dry out. The usual way to make raised beds is by thoroughly churning the soil, but all this digging also destroys valuable humus, disrupts natural air and water channels, and awakens buried weed seeds.

Deep-digging to make a raised bed is justified only where the soil is a very sticky clay, where even weeds cannot thrive. In this case, pile a half-foot depth of sawdust or peat moss on the soil, sprinkle on some fertilizer and lime, then thoroughly mix everything into the top foot of soil. Form permanent beds with paths, and never again set foot on the beds.

Other justifications for raised beds are where the soil is waterlogged or nonexistent (a rocky ledge, for example), or where you want to make a new garden quickly. In these cases, though, no digging is necessary. Begin by mowing any grass or weeds closely. Then lay down a few sheets of newspaper to suppress regrowth and arrange some 6-inch-wide planks on edge for the ends and sides of each bed. Fill the beds with a mix of topsoil, compost, mushroom soil, leafmold, peatmoss, and-or sand, so the resulting soil is rich in organic matter and fertility, and drains well. Fertilizer and lime also might be needed.

Make the beds 3 to 4 feet wide, which is narrow enough so weeding, picking, and harvesting can be done from the paths. Grassed paths are soft and pretty, but must be edged diligently along beds that are not raised. Alternatively, you can cover paths with wood chips, flagstones, bricks, carpet or anything else that will suppress weeds.

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