Do your summer vegetables need a lift?
Raised beds are an excellent way to amp up your harvests.
Few of us have naturally occurring vegetable quality soil. It can be tough to create the rich, loamy stuff in the ground. Instead, start fresh, by building up.
An elevated growing space makes it easier to improve your soil’s fertility and tilth, and to water, weed and harvest crops.
With a few modifications, raised beds protect against rabbits and rodents. You won’t step on productive soil or waste it between rows. You can garden more intensively. And you’ll quickly find that raised beds are easy on the back.
A traditional, stripped-down version is a rectangular wood frame with four posts.
The wood is typically redwood or cedar, although you can get creative with materials. For instance, stone beds are beautiful. But they’re pricey and their thick sides require more space.
Also beware of old, pressure-treated timbers or railroad ties that might leach nasty chemicals.
Given a standard board length of 8 feet, 4 x 8-foot beds are a common size. That width is great for larger, perennial crops, such as asparagus, blueberries and raspberries.
But I think it’s too wide for seasonal edibles, including tomatoes, beans and peppers. You’ll be tempted to plant three rows. But the middle row will be nearly impossible to reach once the veggies gain size. Beds that are 3 x 8, with two rows each, are easier to manage.
As for height: the boards should be at least 1 foot tall and 1 to 2 inches thick. A single, foot-wide board for each side is the simplest approach.
However, to save money, you can stack several narrower boards.
Just be sure the boards are straight and flush, so that soil and water don’t leak out between them.
Use sturdy 4 x 4-inch posts. Cut them 1 foot taller than the height of the bed, to allow for 1 foot to be buried in the ground. If you build a 1-foot tall bed, you’ll need four 2-foot lengths, or one 8-foot post.
Use long wood screws, rather than nails, to connect the boards and attach the posts. Angle brackets at each corner will provide extra stability.
Build your frame upside down on a flat space, such as a driveway or patio, with the posts in the air.
Prepping the Space
Summer vegetables need at least six to eight hours of direct sunlight a day, while winter vegetables need at least four to six hours.
Mark where the raised bed will go, then excavate a foot of soil. Set the frame in place and level it.
The wood should rest on the finished soil level, rather than be buried, which will hasten deterioration.
Line the cavity with quarter-inch or half-inch aviary wire or chicken wire to thwart gophers, moles and other tunneling varmints. Bend the wire up against the interior sides of the frame, then secure the edges with a staple gun.
Also break up any dirt clods in the excavated soil.
The finer the texture, the more easily your edibles can gain a toe-hold in the bed.
The beauty of a raised bed is that you have total control. The soil should be deep, fertile, hold moisture and drain well. It should smell fresh and sift easily through your fingers.
How much? A 3 x 8 bed, 1 foot tall and filled to the brim, requires 24 cubic feet of material. But your soil won’t go all the way to the top. Eighteen to 20 cubic feet is sufficient.
If your garden soil is free of weeds and reasonably loose and fertile, go ahead and “harvest” some.
But at least two-thirds of what goes into your raised bed should be high-quality soil builder, compost and/or topsoil.
Specialty products, like chicken manure and kelp, should be one-third or less. Do not use potting soil. It’s expensive and settles significantly.
If you’re planning to grow your edibles organically, start with the soil. Kellogg’s sells a soil-enriching compost that’s certified organic. E.B. Stone offers an organic flower and vegetable planting mix as well.
Home-made compost, loaded with beneficial microorganisms, is fabulous. But not many of us have 20 cubic feet of the good stuff on hand. Yet even if you only have a bucketful, use it.
Start filling your foot-deep pit with 4 to 6 inches of the excavated soil. Add an equal amount of new material. Mix it thoroughly with a rake or by hand. Try not to tangle with the aviary wire below.
Add another 4 to 6 inches of excavated soil. Mix it in. Add the new material and mix it in.
Continue layering and mixing until you’ve filled the bed to within a few inches of the top.
Run your fingers through it one last time, and you’re ready to plant.
This article was first published in the Summer 2012 issue of Central Coast Farm & Ranch.
Copyright, Joan S. Bolton. All rights reserved. Reproduction of text or photos in any form is prohibited without written permission.