Raised Beds

An Introduction

Raised beds allow for gardening above the level of the surrounding soil; in areas of poorly-drained clay or infertile sandy soils, it is possible to create deep beds filled with fertile, well-drained soil. Elevated above the surrounding ground, they are easier to work without strain; since they aren't walked on, soil compaction is prevented, which in turn allows for significantly more intensive planting than would otherwise be the case. Raised beds can be quite attractive, and make effective gardening available also to wheelchair gardeners.

Mounding the surface is only one way of raised bed gardening, and the easiest. However, other, walled forms of raised beds, also have better drainage than ordinary garden soil, and it may be easier as well as better to build a few, and work the soil under and in the beds intensively. Bricks, concrete blocks, untreated railway sleepers (railroad ties), large logs, all make good and attractive raised bed material.

Soil/Compost/Peat mix in raised bed

Untreated railway sleepers may be used 'as is,' though of course they'll break down quicker than if treated. Such a raised bed is illustrated, i.e. a simple frame constructed from rough-sawn 6x6" hemlock timbers, set on a stony and very heavy clay soil. The soil from inside the frame was removed in small amounts, and mixed by hand with peat moss and compost, to create a very fine, loose, crumbly mixture; rocks were manually removed.

While this takes a significant amount of time and effort, this kind of investment is made only once. The end result, a very well-drained, rich soil that is easily worked and very intensively planted, is still a pleasure to use.

Alternatively, make walls out of concrete panels. Mix 1 part Portland cement with 3 parts pebbles and 3 parts sand; Oil the forms so the panels pop out. Chicken wire can be used for reinforcement.

Cinderblocks also work well, but need to be mortared in place. Hay bales will work, but are even shorter-lived than wood.

About wood preservatives

Keep pressure-treated wood or creosote-preserved stuff away from your veggies. Arsenic-based compounds that have been pressure-forced into treated lumber have been shown repeatedly to leach out into soil in potentially toxic amounts - so why bother when safe alternatives exist?

Organic Gardening magazine published a wood preservative recipe safe for vegetable garden borders:

Mix 1 gallon mineral spirits with two cups of boiled linseed oil and 2 or 3 ounces of melted paraffin. Paint it onto your lumber, in several layers, and let dry a couple of days.

Note that mineral spirits may not be available locally. Do not use paint thinners instead - these solvents can be quite toxic, and should not be substituted.

Mineral oil (used as a laxative and/or skin cleaner, and also known as liquid paraffin) can be used instead, with good effect, and go up on the linseed oil concentration. Linseed oil itself is also quite safe (raw linseed oil may be fed to livestock), but helps protect against sun, water, wind and salt, as well as fungal attack.