Georgia Gardener Newsletter Design Tip: November 1, 2007
|Gardening with Raised Beds
Roses make excellent raised bed plants
I've been working in the same garden for more than 20 years during which time I have focused a great deal of time and
effort to fixing (or creating) the topsoil that was damaged or removed during the construction of my home. Needless to say,
I now have great respect for topsoil and the time it took Mother Nature to create it.
While I'm still willing and able to work on mending the soil in my natural woodland areas, I'm rather impatient and am
looking for a quick fix when it comes to having good soil for other "more manicured" areas of my landscape. I could solve
the problem intially by having several truckloads of good soil brought to my garden, but I would then spend days using
the tiller to incorporate it into the compacted dry clay only to have the clay return after a season or two.....OR....
I could simply build raised beds and for the most part, be done with it. Raised beds also allow me the luxury of
experimenting with plants that can be tricky to grow.
Below are some factors to keep in mind when deciding on whether to use raised beds or not.
Purpose of Raised Beds
Other than convenience, raised beds can open up a whole new world of gardening:
While you can achieve these goals down at the soil level, it's usually much easier in a raised bed.
- Growing plants that don't like the native soil
- Improving drainage
- Controlling the soil quality
- Controlling weeds
- Reducing the need to till and amend
Building Raised Beds
When deciding where and how to build raised beds, you should keep in mind these things:
It should be easily reached from both sides to eliminate the need to walk in the bed.
- No more than 4 feet wide
- A minimum of 3 feet apart
- A minimum of 3-4 feet from a permanent structure
- Any manageable length
*Root crops such as carrots and potatoes may require deeper soil.
- Six inches minimum for flowers and vegetables*
- Twelve inches minimum for trees and shrubs
- Easy access to water, tools, etc.
- Proper sun exposure
- Visibility: do you want it visible to display ornamentals, etc.
There are a wide variety of materials designed specifically for raised beds (and retaining walls) that have both
functional and aesthetic qualities. If your raised bed is going to be in a high traffic area, you may want to consider
using these products. On the other hand, if your raised bed is going to be in a less visible area or be used to grow
edibles, you may want to consider using other products:
*Note: I personally do not use treated wood around fruits, vegetables or herbs.
- Wood: treated* or untreated
- Stone: collected or purchased
- Brick mortared together
- Cinder block: mortered or unmortared
- Decorative material such as Allan Block
Soil for Raised Beds
There are ready-made soil products that you can buy and there are mixes that you can create yourself. Below is a list of
the most commonly used materials for raised beds and their relative costs. I've also included my own recipe that
I like to use in my raised beds.
Note: If you intend to plant herbs, cacti or other plants that require especially sharp drainage, I would add a healthy dose of
coarse sand to your soil mix, perhaps as much as 1/3 of the total volume.
- CLM (Complete Landscape Mix): $$$$
- Bagged Potting Mix: $$$$
- Amended Native Soil: $
- Bulk Screened Topsoil/Planting Mix: $$$
- Special Recipe: $$
Equal Parts: Nature's Helper + Black Kow/Mushroom Compost + Inexpensive Topsoil
In a perfect world with unlimited funds, I would purchase CLM for all my raised beds. I've often joked that you could
put dead plants into that soil and they would grow. However, I've successfully grown many plants using my recipe above.
When determining how much soil you will need for your raised bed, you will need to perform a bit of math:
1. Determine the area (square footage). If your bed is square or rectangular, it's simply length x width.
For example, if your bed is 4 feet wide and 15 feet long, the area would be 4 x 15 = 60 square feet. Any other shape, will
require more involved calculations or you could simply "square" the bed off and estimate the length and width.
2. Determine the volume by multiplying the area x depth. Using the calculations above, if the 60 square foot bed is
going to be six inches (half a foot) deep, then the volume is 60 x 0.5 = 30 cubic feet.
If you're buying bagged products, they should be labeled in cubic feet. Bulk products are often sold by the cubic yard.
A cubic yard is 3 feet x 3 feet x 3 feet = 27 cubic feet. Therefore, the bed above would require one cubic yard plus
3 cubic feet of soil.
Plants for Raised Beds
Raised beds can contain annual plantings such as ornamentals or vegetables, permanent plantings such as trees and shrubs or
a combination of both. I especially like to use raised beds for plants that are fussy about their drainage and suffer
greatly when growing in clay or compacted soil such as herbs or plants native to drier climates. Remember to group plants
within a raised bed that prefer similar growing conditions in terms of sun exposure, moisture requirements and soil.
Installing the Raised Bed
Once you have selected your building materials, calculated how much soil you will need and have chosen a site, you are
ready to begin. It is advisable to take a shovel and break up the ground beneath the raised bed. This will help to
improve the drainage even further. If the area has existing weeds, you might want to consider spraying them with Roundup
and waiting several days before breaking the ground or covering the area with a thick layer of newspaper after you have
broken up the soil.
Once the bed is built and the soil installed, place the plants (still in their containers) in the desired location to make sure
that the spacing and location are to your liking. You are then ready to plant. Remember to stay out of the bed as best as
possible or you will compact the soil. If you are planting seeds, make sure to use string to keep the rows straight and markers
to mark their location.
After planting, water everything thoroughly and cover with mulch. You may want to consider installing a soaker hose beneath
Note: Current watering restrictions still allow for the irrigation of food plots. Newly installed ornamental plantings will
be subject to the current restriction guidelines. Contact your
water company or county for more information.
Maintaining Raised Beds
Depending upon what type of plants you're growing in your raised beds, you are still going to have some maintenance items
- Change Annuals or Vegetables Each Season:
-Summer Annuals/Vegetables: Install After April 15 (watch the weather)
-Winter Annuals/Cool Season Vegetables: Install After September 15 (watch the weather)
- Amend the Soil when Changing Annuals/Vegetables
- Fertilize Annuals and Vegetables Regularly
- Fertilize Permanent Plantings in the Spring
- Maintain 2-3 inches of Mulch
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