By Jan Cashman
With the increased interest in gardening, especially vegetable gardening, we are also seeing an increased interest in growing in raised beds. Our seminars on raised bed gardening always draw crowds. Local climate and soils make raised beds a great way to garden here.
Why a raised bed?
The soil in a raised bed garden warms up quicker in the spring, important in our short growing season. A hooped cold frame, simple to construct over your raised beds, adds even more heat and increases your growing season. It is easy to amend your soil by mixing in organic matter before filling the beds. Because raised beds sit above ground, drainage is improved.
Raised beds save space; you can plant your plants closer together in a raised bed garden. There is no need for paths through your raised bed because you do the work from its sides.
As we get older, bending down to work in a garden gets harder. Raising the garden makes it easier to plant, weed, and harvest your crops. Children love to work in a raised bed garden—12” is just the right height for them. Building a raised bed up to 24” makes a perfect height for the wheelchair bound.
Most vegetables and flowers need full sun, so pick a sunny site for your raised bed garden. Four feet is the most common width, to allow you to reach the middle from both sides. Height is commonly 12-24”, depending on the dimensions of the lumber you use. Length is up to you and the space you have.
You can build your raised bed over existing grass, but it would be better to kill the grass underneath the bed and loosen up the soil. If your soil is heavy clay, you may want to place gravel underneath the beds for better drainage. Raised beds do not need a bottom.
Long lasting cedar or redwood or pressure treated timbers are commonly used for constructing the sides and ends of raised bed boxes. The corners of wooden boxes will need to be reinforced with rebar, 4 x 4s, corner braces and lag screws to keep them from caving out. Materials such as keystone blocks, bricks, or stones make attractive alternatives to wood. You might even have some recyclable materials on hand you can use to construct your raised bed. Prebuilt raised beds are available that are light, attractive, and require no assembly.
A good, readily accessible soil mix to use in your raised beds is ½ compost and ½ topsoil. For even more organic matter, use 1/3 compost, 1/3 topsoil, and 1/3 peat moss. Perlite, vermiculite, or gypsum can be added to lighten your soil mix.
What to plant in your raised bed garden:
Tomatoes and peppers love the warm soils of a raised bed garden. Carrots, onions, lettuce, spinach, beans, in other words, most vegetables, can be grown in a raised bed. Sweet corn will grow fine in a raised bed, but takes up a lot of room, as do pumpkins and squash. Vegetable crops, especially tomatoes, potatoes, and peppers, should be rotated into a different raised bed every 3 to 4 years.
Try growing herbs in your raised bed. The compact plants of basil, sage, parsely, rosemary, thyme, or any herb will grow well in the warm soil. Plant marigolds with your vegetables to detract pests. Or, forget the vegetables and plant the whole thing in beautiful annual or perennial flowers.
Raspberries are often planted in a raised bed to contain their suckers. The well-drained soil of raised beds makes them a great place to grow delicious strawberries. It is hard to keep weeds out of a strawberry patch; planting them in a raised bed will make the weeds easier to control, and picking the berries will be easier, too. Plant inexpensive, bare root strawberries in your raised bed in April or May, spaced as close together as one foot. Choose hardy varieties of strawberries such as Cycone, a Junebearing variety recommended for high altitudes, or Ogallala and Quinalt, tried and true everbearing varieties for our climate which bear lots of sweet fruit in early summer and again in August.
Start planning and building now so you can plant your new raised bed garden in May and enjoy the fruits and vegetables of your labor all summer.