The Advantages of Raised-Bed Gardens
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The following is an excerpt from Mortgage Free! Innovative Strategies for Debt-free Home Ownership, Second Edition by Rob Roy. It has been adapted for the Web.
French intensive or “biodynamic” gardening involves the use of several “raised beds” of about four feet in width—the maximum width allowing the gardener to reach the center from either side—and virtually any length, although eight to twelve feet is common. We once built a raised bed thirty-two feet long with occasional “crosswalks” to facilitate moving around the garden. Ideally the beds should have at least twelve inches of good soil to turn each year, although that varies somewhat with the crop. Beds can be either permanently framed with stone or wood, or shaped with a rake and a spade each season. We like the “permanent” beds, but we’ve also seen many excellent gardens of mounds reshaped each year at the time of turning. The advantages of raised beds are:
- Less land is needed. Intensive planting is possible because no space between rows is required, yielding much more produce per square foot of garden.
- Seeds or seedlings are spaced so that the young plants form a living “green mulch” over the bed, discouraging weeds and helping to retard moisture loss through evaporation.
- Gardening is three-dimensional: leafy vegetables are alternated with root vegetables so that both the surface and the subsurface spaces are productive.
- Each bed can be tuned to the proper pH factor (acidity vs. alkalinity) for the particular vegetables to be grown in that bed. Lettuce likes sweet soil, for example, while strawberries prefer acidic soil. Certain special mineral requirements can also be economically satisfied by concentrating them where needed.
- Much less watering is required because of the lack of runoff and reduction of evaporation. This advantage is greater with the permanently bordered raised beds, as opposed to the mounded method. In combination with drip-irrigation watering methods, the advantage is compounded.
- Much better use is made of mulch and compost with intensive gardening. Good soil is built up faster.
- No rotary tillage is needed. The beds are easily maintained with a spade, rake, and small hand tools. The raised beds are easier to work on because they are ten to twelve inches above the permanent walkways.
- Pest control is simplified because the growing area is contained and compact.
- Raised beds are aesthetically superior. They stay neat and tidy with the permanent walkways. Very little weeding is required.
- In combination with a built-on protective cover and the use of rigid foam insulation around the inside edge of the bed, growing seasons can be greatly extended. Jaki and I use a plastic sheet over a light bamboo frame to extend the season or to grow vegetables that require more heat, such as peppers.
Image courtesy Relocalize.net.
May 8th, 2009 at 9:45 am
I’d add a couple things. 11) by establishing distinct and permanent paths, the growing areas are never walked on and therefore the soil never compacted. Plants grow significantly better (faster, healthier, more productively) when their roots don’t have to contend with compacted soil). See this article–it’s targeted towards corn farmers, but the concepts carry over to vegetable gardens. Note, in particular figure 4 a little ways down the page on the right-hand side. For home gardeners, drought isn’t usually an issue since we don’t rely only on rainfall to water the garden. So the dashed line situation (showing some possible advantages from mildly compacted soils) doesn’t much apply. Our situation is basically confined to the solid line, which shows consistent reductions in yield as soil is further compacted.
12) related to point 10, a raised bed warms faster in the Spring (even without covers), and so can be planted sooner and seeds will germinate more robustly.
13) when you establish your raised bed, especially the permanent boxed in kind, you can combine the bed with “lasagna” style sheet mulching to suppress the grass and weeds that are underneath and fill with clean materials above. That means that not only can you adjust the mineral proportions (point 4 above), but your infill can be pretty nearly weed free (for example if you use finished compost rather than topsoil). So you have less weeding to contend with, and any weeds that do arise will be from seed rather than roots and therefore easy to pluck out and be done with. Naturally, new weed seeds will blow in on the wind each season, so you’ll never totally avoid weeds, but you do get a leg up on them.
May 10th, 2009 at 1:48 pm
I just read another article on the subject of raised beds. Gene Logsdon doesn’t think they are so great after all..
http://organictobe.org/index.php/2009/04/29/down-with-raised-beds/