Raised garden beds provide an enclosed space elevated a few inches to a couple of feet above the ground, in which to grow edible or ornamental plants. They can come in any variety of shapes, sizes and materials, and can be pre-made or self-constructed.
Types of Raised Garden Beds You Can Build
There are 4 basic types of raised garden beds: raised ground beds, supported raised beds, containerized raised beds, and elevated raised beds (ideal for wheelchair use).
Advantages of Raised Garden Beds In Your Garden Planning
One of the key advantages of raised beds is the control you can have over your growing environment. You can raise the beds to heights that allow you to have easier access to them, along with placing them in the best site location for the type of plants you’re growing. Raised beds can also be more productive than in-ground beds because the soil can be managed for nutrients, weeds, compaction and drainage along with the fact that the soil often warms sooner in the spring, giving plants an earlier start in the seasons.
Downsides to raised beds include some plant limitations based on size, and – depending upon the type of beds you’re creating – cost.
Site Location for Successful Raised Garden Beds
Like any garden, you’ll want the location of your raised bed to get at least 6 hours of direct sunlight each day. You’ll also want to have your garden bed near a water source, such as a hose or rain barrel, but avoid placing it by where rainwater collects or stands. Set your bed in a place somewhat sheltered from wind, such as a by a tall fence, structure or close to trees or shrubs that act as windbreaks.
How Big Should Your Raised Garden Bed Be?
Most beds are between 12-20” in depth, since many vegetables require at least a foot or more of soil to support their root systems and thrive. Keep beds no more than 3-4 feet wide so you can easily reach an arm’s length – about 1.5 feet – to access plants at the center of the bed. The length of your bed can be flexible. Most gardeners like to keep them between 4-6 feet long, with about a 3′ space around each bed so you can easily maneuver around them, squat or sit comfortably beside them and/or move gardening equipment such as wheelbarrows easily around them. You may want to consider mulching the space around your beds with wood chips or crushed stone to keep weeds at bay.
Best Garden Bed Materials
There are many options for garden beds, from prefabricated ones you can purchase at your local garden center or online, to self-constructed options. Wood is one of the most popular materials for raised garden beds. The best options include rot-resistant lumber such as cedar, cypress, redwood, oak or locust.
Avoid pressure-treated lumber since it can leach heavy metals into the soil that can be taken up by the plants, a particular concern if you’re growing vegetables or herbs to consume. Also avoid using MB (Methyl Bromide) labeled pallets for their toxicity. HT (Heat Treated) pallets are safe to use. Wood railroad ties should be avoided since they contain creosote which is harmful to humans and plants.
Salvaged cinder blocks, made from fly ash, contain arsenic, lead, mercury and other heavy metals that are dangerous. Modern day concrete blocks have a similar look but are safe to use in the garden. You can also consider making beds from brick or stone.
If you’re purchasing a pre-made bed, options include wood, galvanized steel and composite materials. Galvanized steel has a much longer life than wood, lasting as long as 25+ years – almost 3 times that of wood.
How to Fill Your Raised Garden Bed
Soilless potting mix can be an expensive choice to fill an entire raised bed with. Many gardeners choose to have a topsoil/compost mix. A combination of two-part topsoil to one-part compost is ideal. You can add one part sand or perlite and one part compost or peat moss to two parts soil from your yard. This mixture will ensure good aeration and oxygen for proper root development. If you’re using a bed that has a closed bottom, make sure it has adequate drainage holes – there’s no need to layer the bed with rocks or crushed stone.
Include a slow-release granular fertilizer when you first plant, then fertilize again about 3 months later. Add a 2” layer of mulch around your plants to help retain moisture and prevent weeds.
Plan Your Plants for Your Raised Garden Bed
You’ll get the most from your raised garden bed by planning out your plantings. You don’t want to have to try to reach past a tall tomato plant to get to your carrots. You can either organize your plants from lowest growth to highest or have your tallest plants in the center with shorter ones on either side. If you do have plants that are tall or dense, be mindful of any shade they might cast on surrounding plants. Check companion planting guides to optimize plant growth.
Plants to Choose (and Avoid) for Raised Garden Beds
Moisture-loving plants that do well in raised garden beds include cardinal flowers, sedges, and monkshood. For dry spaces, choose Russian sage, coreopsis, false indigo, big bluestem, and Mediterranean herbs like rosemary, lavender and thyme, as well as succulents such as sedums and echeverias.
You can grow fruits including compact varieties of berries like strawberries, raspberries and blackberries and most varieties of tomatoes. Root vegetables like carrots and radishes and leafy greens like lettuce, arugula and kale also do well in raised bed. Perennials such as salvia, tickseed, Montauk daisy and Siberian iris can make for a beautiful raised bed cutting garden.
Plants that grow large, are wide and/or tall aren’t the best choices for raised garden beds. Included in this list are corn, broccoli, melons, cauliflower, and squash, to name a few.
General Tips For Raised Garden Beds
- If you are building an elevated bed drill ¼” holes in 9″ to 12″ intervals in each direction.
- If you have a ground bed, place a few layers of cardboard or some weed barrier cloth prior to filling the bed with soil to discourage weed growth and pests.
- Don’t line your garden beds with plastic since this can hinder drainage and cause root rot.
- Water your plants at their base, rather than using a sprinkler which tends to wet leaves that can encourage fungal growth.