By JASON GRAVES
Horticulture Extension Agent, Central Kansas District
With more and more people interested in growing their own vegetables it is common to find that many gardeners in cities have only a little backyard space to utilize and thus a raised bed is called for. Growing in raised beds gets the attention of gardeners not only for space saving reasons, there are actually many other advantages to this type of gardening.
Advantages
Raised bed gardens offer several advantages over conventional gardening plots. Soil raised above ground level warms up more quickly in the spring, which allows for earlier planting dates. The beds are filled with high-quality soil mixtures which improves drainage and increases yield. Raised beds are smaller than traditional gardens making them easier to maintain and denser plantings help reduce weed infestations.
Getting started
Getting started with raised bed gardening isn’t difficult. There are many styles of raised beds that can be easily created. Wood is most commonly used, but cinder blocks, landscape timbers, rock, bricks and many other materials can work just fine.
Treated lumber used to contain arsenic and chromium which was considered unsafe in food gardens, but now most lumber is treated with the wood preservative ACQ (Alkaline Copper Quaternary) which is generally considered safe to use for raised bed gardening. If you are uncertain about the safety of treated lumber, place a heavy plastic liner between the treated lumber and the soil used for growing plants to prevent direct contact of plant roots with the treated lumber. Another option is to use a naturally rot resistant wood such as cedar.
Raised bed don’t even have to have a frame at all. You can build unframed (mounded) raised beds by tilling the existing garden soil 6 to 9 inches deep. Then add 2 to 3 inches of organic matter to the raised bed row and till it into the soil. This will have the effect of raising that area above the surrounding soil. Add soil and organic matter as needed to create mounded beds that are 8 to 12 inches above the surrounding soil and 3 to 4 feet wide. Walkways between unframed raised beds should be wide enough to accommodate a wheelbarrow. Spread a layer of mulch such as bark or straw over the walkways to reduce weed growth and mud problems.
Another option that is becoming more popular are galvanized steel raised bed gardening kits. These are easy to put together and strong and make an excellent choice for home gardeners. They come in many different shapes and sizes.
Dimensions of raised beds can vary according to the site. Common dimensions include 4×4, 4×8, or 4×10 sized beds. The 4-foot width or a little narrower is preferred because it allows for an easy reach into the bed from either side to tend the plants. This keeps soil compaction from occurring because the garden soil is not walked on.
The depth of a raised bed is important. Regardless of the material used to build the bed there needs to be enough soil depth to accommodate the type of plants to be grown. For most vegetables a soil depth of 12 inches is generally sufficient but 15 to 18 inches is even better. If bending or stooping is a problem for the gardener, a deeper bed can be built that allows for gardening in the standing position.
Raised beds can be made wheelchair accessible by making the walls about 2 feet tall and limiting the width of the bed to about 3 feet.
Soil Mix
The biggest advantage of raised bed gardening is the opportunity to mix and amend your own soil. Most often a 50/50 mix of good quality topsoil and organic matter such as peat moss, compost, or composted manure creates a wonderful growing media that drains well and is easy to work in. Another popular raised bed mix includes 1/3 top soil, 1/3 compost, and 1/3 drainage increasing material such as perlite, vermiculite, bark, or coarse sand.
Location
As with any garden site, the bed should be located in full sun for best production. The best location also provides wind protection. Summer winds can take their toll on vegetable crops. A tree, shrub screen or border will work if it is on the south or southwest side to protect the garden. If possible, raised beds should be also located where there is easy access to a water source. Raised beds can tend to dry out more quickly than traditional gardens and should be monitored for moisture needs regularly. A drip system is an efficient and easy way to provide irrigation to raised beds.
If you haven’t tried raised bed gardening, now is a great time to get started. This gardening method provides great success and is a flexible way to plant, grow, and harvest your own homegrown produce. Check out the Raised Bed Gardening publication below for more information.
Raised Bed Gardening (pdf)
Vegetable Garden Planting Guide
Another publication that gardeners may also want to refer to is the Vegetable Garden Planting Guide. This guide has all the basic information for planting garden crops in Kansas.
Vegetable Garden Planting Guide (pdf)
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Jason Graves' Central Kansas Lawn & Garden blog is republished on Salina Post with permission. For more lawn and garden information, visit the Central Kansas District Extension website.