For many home gardeners, raised garden beds may seem like a lifesaver. To a casual observer, they look like they provide all the benefits of a typical backyard garden but with much less hassle. The truth, however, is a little more complicated.
Common problems with raised beds include irrigation, construction costs, soil quality, limited plant options, and increased manual labor compared to in-ground beds. Each of these issues is easily overcome but should be factored into considerations of raised-bed gardening.
Gardeners who use raised ground beds often face the same challenges as gardeners who use traditional in-ground methods.
Growers who use supported raised beds and containerized raised beds, however, face a different set of challenges.
Problem: Keeping Your Raised Beds Irrigated
By far, the most common problem with raised beds is their tendency to dry out quickly.
Raised beds absorb heat from all sides, which increases the amount of water lost through evaporation. Traditional in-ground gardens, on the other hand, only absorb heat from above. During the hottest days of summer, in-ground gardens will lose water to evaporation, but not at the same rate as raised beds.
Furthermore, in-ground gardens can retain larger quantities of water because the water is not limited to a defined space. Raised beds, particularly containerized raised beds, drain quickly. In the height of summer, raised beds that were watered in the morning may be completely dry by evening.
Depending on the size of your garden and your plants’ needs, it will take much more water to keep your raised garden irrigated than it would take to irrigate an in-ground garden (source).
What You Can Do
First, when planning your raised bed garden, think about the irrigation needs of your plants. Group them according to how much water they need to help you avoid over or underwatering your plants.
Plan to water at least once a day, especially during hot, dry periods. Water slowly and thoroughly to give your plants’ roots as much water as possible. If you can, avoid watering during the heat of the day to prevent excessive evaporation loss.
Many drip irrigation systems and soaker hoses work well in raised bed gardens. Drip irrigation systems (link to Amazon) are particularly effective at delivering water to your plants slowly, giving the roots plenty of opportunities to take the water in before it evaporates.
You can also add mulch and organic matter to help your soil retain moisture. Mulch has the added benefits of moderating the soil’s temperature and reducing the weed population (source).
Problem: Construction Costs and Quality
A major disadvantage of raised bed gardens is the up-front cost of getting started.
If you do not already have the materials, you will have to buy them. A quick internet search shows a variety of raised beds available from retailers in prices that range from as low as $50 to as high as $500 per bed. These costs will rise quickly if you add decorative stone or other similar elements.
Many gardeners choose to forgo prefabricated raised bed kits and build their own, but this can be costly as well. Raised beds need lumber that is two inches thick; one-inch boards are not hardy enough.
Furthermore, there is the issue of quality. Untreated lumber is cheaper than lumber that has been treated with a preservative, but it will degrade quickly. Within just a few years, you will need to start over with new raised beds.
However, this raises yet another concern. Whatever chemicals are on the wood will make their way into the soil. If you intend to follow USDA Organic guidelines, treated wood is a non-starter.
Likewise, while telephone poles and railroad ties have been popular raised bed materials, you may wish to avoid them. Telephone poles and railroad ties leach toxic creosote into the soil, which finds its way into many edible plants (source).
One idea that has become popularized by social media is using discarded tires as child-sized raised beds. This is not a safe idea, especially if you want to grow vegetables. Tires leach all kinds of harmful chemicals into the soil, making it unsuitable for use in a garden.
Be cautious about using recycled or reclaimed wood as well. While this may seem economical and eco-friendly, if you do not know what has been used to treat that wood in the past, don’t use it in your garden without a protective barrier (source).
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What You Can Do
Before you invest any time or effort, go into raised bed gardening knowing that it is precisely that–an investment. Raised beds will always cost more than in-ground gardens, but they can certainly be worth the investment.
If your budget is low, and you are not bothered by the aesthetics, consider building your raised beds out of pallets, upcycled cattle troughs, non-flimsy kiddie pools, or halved plastic barrels. These will not look as attractive as some of the pricier options, but if you drill drainage holes in the bottom, these containers can work well.
If you want to buy or build one using untreated lumber, understand from the beginning that you will need to replace your raised beds every four to six years (source).
Treated lumber can last quite a bit longer, and not all treated lumber is harmful! Two of the most common lumber preservatives are ammoniacal copper zinc arsenate (ACZA) and ammoniacal copper quat (ACQ). Both of these compounds are safe to use in raised vegetable gardens.
Reputable manufacturers and retailers will be able to tell you what preservatives have been used on the lumber. If you want more information, consult a local Extension agent or horticulturist who can tell you more about what is available in your area.
Many gardeners who are still leery of treated lumber use plastic sheeting as a barrier between the soil and the wood. If you choose to do this, make sure the plastic does not prevent water drainage.
If you choose to forgo wood altogether in favor of bricks, stones, or cement blocks, your financial investment will be much higher. However, that investment also buys you more time, as brick, stone, and block are more durable than wood.
Problem: Soil Costs and Quality
In addition to buying construction materials, raised bed gardeners must also buy soil, often in huge quantities.
A raised bed that is 32 cubic feet (4’x8’x1’), a pretty common size, requires nearly that much soil as well. Put another way, that’s approximately 192 gallons of soil.
High-quality garden soil for a raised bed that size will become expensive quickly, which makes bulk topsoil a more appealing option. Bulk topsoil is significantly cheaper but is often much lower quality.
Bulk topsoil is usually sourced from poor-quality sites, which means there is a decent chance that, without soil amendments and conditioners, it can’t sustain a healthy garden. Sometimes, bulk topsoil is not even real soil, but rather a combination of sand and bark compost.
Mulch is an additional expense, and so is compost if you do not already have some. It is not unusual for gardeners to spend around $200, possibly more, on soil, mulch, and compost during their first raised bed season.
What You Can Do
Again, expect the start-up costs to be high. With proper care and maintenance, the investment will be worth the return.
If bulk topsoil is the best choice for your budget, do a little research before you buy. Ask a local expert for recommendations and only buy from reputable sources. Add compost and other organic material to improve the quality over time.
You can also avoid low-grade bulk topsoil without paying top dollar. Often, mid-grade garden soil with some added compost works well for raised bed gardens.
Another option is to make your own planting mix out of peat, vermiculite, bark, sand, and other materials. The materials you will need vary by what you intend to plant, and you should plan to include some soil as well. The Alabama Cooperative Extension Services offers several potting mix recipes that may work for your raised beds.
Problem: Limited Vegetable Options
Depending on the size and depth of your raised beds, you will find that not all veggies are well-suited to raised bed gardening.
Vining plants, like pumpkins, squash, and melons, need plenty of space and take over a raised bed very quickly. Corn is also not well adapted to raised planters because the containers are too shallow to allow for adequate anchoring in the soil (source).
You may have success with cucumbers and tomatoes if you add cages or trellises to allow them to grow upward. However, this may not work well in raised containers.
Furthermore, because there are limited vegetable options, there is a higher risk of soil-borne disease due to lack of crop rotation.
What You Can Do
Plan your raised bed vegetables strategically. Plant small cold-season vegetables, like lettuce or radishes in between larger warm-season vegetables like tomatoes and peppers. By the time the tomatoes and peppers need the space, the lettuce and radishes will be finished for the year.
You can also maximize your space by planting seedlings equidistant (equal distance) from each other rather than creating rows. Other experts recommend circular or block patterns to make the most of your available space.
There is another benefit to using a planting pattern in your raised beds. Equidistant spacing cuts down on the high density of leaf coverage that sometimes occurs in small gardens, thereby cutting down on the pests that thrive in high-density foliage.
If you have concerns about crop rotation, try alternating vegetables with herbs and flowers. Many gardeners use raised beds exclusively to plant herbs, and a huge variety of flowers thrive in raised beds, as well.
Problem: Manual Labor
Because of their supportive structures, tillers, hoes, shovels, and other large tools are difficult or impossible to use with raised beds. This is, of course, particularly true for containerized raised beds.
This means that all tilling, planting, weeding, and mulching must be done with hand tools and elbow grease. Hand labor may not be a deal-breaker, but it is important to keep that in mind before you construct a raised bed.
What You Can Do
When you choose a planter design, make sure that you can reach all parts of the interior from the outside. Then, choose a location for your planters that allows for access on all sides (i.e., not flush against a wall).
If you use a wheelchair, walker, or another assistive device, plan to space your beds about 36 inches away from walls or other planters to allow plenty of space to move and work comfortably (source).
Strategic planting can help here, as well. If your raised planters are fairly large, plant perennials near the center and annuals around the borders. This provides easier access to the plants that will need the most work.
Why You May Still Want To Try Raised Beds
Despite these issues, Raised beds offer plenty of advantages, including the following:
- Improved accessibility for growers who use wheelchairs or have other mobility barriers.
- Greater control over soil quality. This is especially welcome news for growers whose soil drains poorly, has a history of soil-borne disease, or is otherwise not suitable for most plants.
- Improved weed control. Weeds are much easier to manage or eliminate completely when there are significant barriers between the garden and lawn.
- Efficient use of available space. Raised beds are especially popular with gardeners who have small yards or no yard at all.
- Earlier planting dates. Soil in raised beds warms up more quickly in the spring, giving gardeners a jump start on the growing season (source).
Raised beds vary in size, shape, and depth, but generally fall into one of three categories:
- Raised ground beds. These look like mounds of soil and compost right on the ground that rise about eight inches high. They do not require wood or any other materials besides soil.
- Supported raised beds. These are similar to raised ground beds in that they also rest directly on the ground, but the mounds are supported by wood, bricks, stone, or another material. The supports allow gardeners to make the beds larger and deeper than a raised mound.
- Containerized raised beds. These are large planters, usually made of wood, that may rest on the ground but are commonly built with legs that raise them to the desired height (source).
Raised bed gardening can be extremely rewarding, especially for gardeners with limited space, limited mobility, or poor soil quality. But it is not without its drawbacks: increased irrigation, high start-up costs, restricted planting options, and extensive manual labor.
Before you begin, research different planter options to find the kit or materials that will best suit your budget and your intended crops. The initial expense and effort are steep, but the long-term gains are worth it.