Raised bed gardens are a great way to make gardening more accessible and easier to manage. They are available in many forms, and with the right preparation you can guarantee a successful growing season. There are a few issues to consider, but with a little planning ahead of time the benefits vastly outweigh any cons that come with raised bed gardens.
What is a Raised Bed Garden?
Raised Bed Gardens are a style of gardening that became popular in France and England in the 18th century, and have regained popularity in the last 50 years with modern home gardens. The idea is to plant flowers and vegetables above the ground in a well-thought-out soil mixture, rather than tilling and amending the ground below. This can be achieved by mounding the soil up into 12” high rows, by building a 12” – 24” tall frame and filling it with soil, or by planting in a large planter, made up of a 12” – 24” deep container that stands on four legs and comes up waist-high. All three of these styles offer their own benefits – choosing between the styles is up to an individual’s space constraints and personal preferences.
The planters on legs work perfectly on decks, balconies, and surfaces that don’t offer any drainage. The built-up frames work well in situations where pests can be an issue, the ground is difficult to dig in, or bending over a garden could cause discomfort. Mounding soil into smaller raised rows for a garden is very cost-efficient as no structures need to be built, and they still offer many of the same benefits of the other two styles.
Why Use A Raised Bed Garden?
The number one benefit of raising a garden bed above ground is the complete control a gardener has over the quality of the soil they are working with. This is one of the easiest ways to guarantee that your soil is made of a careful balance between topsoil, compost, and organic matter. Since you are not walking on the soil, raised beds also offer the added benefit of soil that isn’t compacted and remains fluffy and loose for adequate drainage.
Other benefits include:
- A better sense of control over the size and scope of the garden, which can help beginners feel less intimidated
- It makes it easier to grow edible foods in small spaces
- The soil warms up sooner in the spring, helping create a longer planting season
- Growing is easier on gardeners with stiff joints or other health issues that make bending, kneeling, or digging more difficult
- It’s easier to prevent pests with walls, fences, covers, and chicken wire around the planters
- Better control over nutrients can help ensure better yields and larger, longer-lasting blooms
- By changing the material used to build your structure, water retention can either be increased or decreased depending on what you need for your local environment
- An attractive raised bed or raised planter can work to complement your landscaping by adding a sense of structure, similar to what hardscaping or retaining walls do for garden design
What’s the Best Material To Use For A Raised Bed Garden?
For mounded raised beds, the best material to use is good quality soil, a fence to keep out deer and rabbits, and perhaps a few structures and trellises for climbing vegetables. They’re wonderfully low-impact regarding set-up time and cost!
Make sure that the ground you’re using is already level, it receives lots of light, and that it is easy to prevent weeds or grass from growing up into the mounds. Don’t build a mounded raised bed on asphalt or other places with no drainage, or on lawn or sod that can introduce weeds. It’s still a good idea to amend the sub-soil somewhat, using no-till methods for increasing drainage and directing water flow. Mounds can also be made taller by layering logs and sticks underneath the soil.
For raised planters, you’ll simply need a quality planter made out of weather-proof, lightweight material (resin makes for a good durable replacement to regular plastics) and a sunny place to grow your veggies. Planters that offer good drainage and small supports through the middle will last longer and keep your plants healthier.
Things are a little more complex when planning and building a supported raised bed that sits on the ground and is surrounded by an outside structure. The perfect material would be organic, chemical-free, environmentally friendly, inexpensive, easy to adjust, easy to build, and long-lasting. It would let just the right amount of water drain, be sturdy enough to sit on, and block pests with ease.
Unfortunately, no one material has achieved a perfect score. Each choice has something different to offer, and it’s up to the individual gardener to decide which challenges they would rather handle.
Pros & Cons Of Various Materials
Pros: Organic and sturdy, can be built into almost any shape imaginable, less expensive than other wood options.
Cons: Won’t last as long as other types of woods – will rot sooner unless painted with a waterproof finish. (Modern finishes can often contain chemicals that can be leached into the soil.)
Untreated Cedar, Oak, Cypress, and other Rot-Resistant Woods
Pros: Organic and sturdy, can be built into any dimensions needed, will last the longest of any untreated wood option. Permeable, allowing water to pass through (similar to terra cotta). One of the most popular options.
Cons: On the expensive side, whether or not you buy them pre-assembled or do-it-yourself. Lots of setup/construction is required. Sometimes these woods are sourced from old forests and are not the most sustainable choice. They will last a while, but contact with moisture will cause rot over time – especially in wetter, humid climates.
Pros: Sturdy and long-lasting. Cons can be mitigated with plastic wrapping sides. Newer, modern types of pressurization systems are less toxic. Sometimes less expensive than untreated, rot-resistant woods.
Cons: If you choose PTW, you have to make sure it has been made very recently. Older techniques for making wood weatherproof included using chemicals that are carcinogenic: that is less of an issue for a fence rail but a much bigger issue when it’s a border to a garden with edible food. Railroad beams have the same toxic issue.
The chemicals in newer pressure-treated wood aren’t as bad, but are not great and will still be leached into the soil through moisture. Gardeners can keep non-edible plants in these planters, but edibles should be kept in the center of the bed, or the wood needs a plastic liner. Plastic liners increase water retention, which can be good or bad considering humidity levels. Never line the bottom of a raised bed with unperforated plastic. Lining the sides with canvas or fabric will just hold moisture onto the wood and make the leaching potentially worse.
Brick or Stone
Pros: Lasts a very long time, is very sturdy, and has a very attractive look. Shares all the same water-retention and erosion-prevention benefits of a retaining wall.
Cons: Difficult and time-consuming to build. Very permanent – if you don’t like where you put your bed it would be a major chore to reorganize. Putting pavers or brick underneath the bed would not allow enough drainage.
Pros: Lightweight, long-lasting, easy to find, relatively inexpensive, and available in a lot of size options. You can save even more by drilling drainage holes into a livestock water trough available at farm supply stores. The galvanization process also involves chemicals, but it is usually zinc and if it leaches into the soil in trace amounts, plants need zinc anyway. Relatively easy to set up. Taller styles can bring the garden up to waist-high, making it easier on those who can’t bend over to the garden. Very popular choice.
Cons: Slightly less sturdy than wood boards – gardeners won’t be able to sit on the edge while gardening. Much more difficult to build custom sizes or shapes. Needs support built-in, holding sides together in order to hold the weight of soil and water. Not permeable on the sides, so they need great drainage underneath in order to not retain water for too long.
Those are the most popular choices. If you know of any options not listed here, share them in the comments below!
How Should I Fill A Raised Bed Garden?
The most important thing to take your time with is deciding the layers that will go into your raised garden bed. It actually isn’t always a good idea to just buy a solid cubic yard of topsoil and call it a day: there isn’t enough organic material to allow space and drainage, and there may not be enough compost or other nutrients to supply the local organisms with the nutrients they need to thrive.
We recommend a mix of either 50%/40%/10% or 65%/25%/10% topsoil/compost/organic matter. This will help create the open, loamy structure and nutrient richness that makes up great soil.
Options for compost include leaf compost, pine fines, or worm castings, among others. Ideal options for the organic material include fir bark, orchid bark mix, perlite, vermiculite, peat moss, cedar shavings, leaves, or similar materials. When planting your garden, you can use Espoma Bio-tone to introduce healthy mycorrhizae that benefit young root structures. Then, use garden-friendly fertilizers that add more phosphorus and potassium than they do nitrogen.
A great way to save money is to layer sticks, logs, leaves, and cardboard into the bottom of your raised bed before you add 6” – 18” of your soil mixture on top of that. This will allow great water drainage and help you save while still making it difficult for pests or weeds to reach your plants.
A Note About Drainage:
It’s important to make sure the ground below the bed isn’t blocked, but that alone might not ensure good drainage. If you are concerned about the ground in your area having a high clay consistency (as many places in Maryland do) and retaining water, don’t forget to dig a small trench underneath that will allow water to run downhill away from the raised bed. You can even have it flow into a french drain and fill the trench with stones and gravel.
How Do I Keep Pests Out Of My Raised Bed Garden?
The main pests that raised beds can help against are rabbits, deer, and groundhogs. (Moles are really only a bother if you don’t want them to disturb your soil or lawn as they hunt for grubs). These critters get the munchies but they can only eat what they can reach – if they can’t reach your garden they can’t eat your plants! Fence off the area with a 4’ – 5’ tall wall of chicken wire or similar material. Keep the fence close to the beds if you can – even if deer can jump the fence, if they do not have a big enough area to land in they usually will not jump over it.
To protect your plants against smaller pests, you can introduce companion flowers, predatory insects like native ladybugs, or you can spray your plants with organic Neem Oil on a regular basis. Broken eggshells and/or diatomaceous earth around the outside of the raised bed edge will help mitigate slugs and other crawling pests. To prevent fungus and mold, water plants at the soil level, keep foliage dry, and keep mulch away from the stems.
Is A Raised Bed Garden Right For Me?
- Do you live in an apartment or condo and all you have is a sunny balcony?
- Do you have a home with a small yard and you need to be efficient with space?
- Do you want to dip your toe in the gardening water without going overboard at first?
- Do you want to enjoy the mental health benefits of gardening?
- Do you like the idea of mixing your own soil instead of tilling, digging, and amending the soil near your home?
- Do you want to grow your own vegetables, cut flowers, or berry shrubs?
If you said yes to any of the above, there’s a really good chance you’ll fall in love with raised bed gardens too! Come into Patuxent Nursery so we can help get you started on the right foot. Our team can help match you with the right soils, fertilizers, amendments, seeds, supports, pest controls, and other tools to make your raised bed gardening a breeze.