Raised garden beds are popular for a reason – they’re an amazing choice to grow so many types of veggies, herbs, and flowers! When planning a new raised garden bed, size is often one of the first things decided upon but is often given little consideration. While premade kits come in various sizes, if you DIY, you’ll have to pick the size yourself.
3 common mistakes when sizing a raised garden bed
Installing a raised garden bed can be easily accomplished by a gardener of any experience level, but it is a much bigger undertaking than planting a hanging basket or container pot. A poorly designed raised bed can be a problem for years, so here are a few mistakes to avoid while planning yours.
Too Wide
We know it’s tempting to build a super wide raised bed to fit even more of your favorite plants! Building a raised bed that is too wide is easy to do and hard to fix. For most of us, our comfortable reach is about two feet. Since part of the appeal of a raised bed is loose, compaction-free soil, stepping or kneeling in your raised bed is a no-no.
Keeping raised beds at or under four feet wide is easy when using wood, as standard lumber dimensions make cutting an eight-foot-long board in half for the ends a snap. One of the most common DIY bed sizes is a 4’x8’ for that reason.
Beds built of other materials, or in non-rectangular shapes are easy to get too wide. Round edges, non-linear shapes with curves and sweeping lines, all these ideas are excellent design elements but can result in that unreachable section in the middle of the bed–I’ve done it several times.
Sketching the idea on graph paper can help prevent your design process from outgrowing your arm’s reach. You’ll be able to see the widest portions of the bed and adjust accordingly.
Too Long
How can a raised bed be too long? Imagine walking twenty feet down to the end, then twenty feet back up to the middle on the other side where you left your tool, and then walking around to get back to where you started.
Raised garden beds that are too long can become a nuisance. They also tempt people to take a shortcut and step in the beds to get across. Consider keeping your beds short enough that going around them isn’t a chore. Two twelve-foot-long beds are more manageable than one 24-foot bed.
Too Shallow
You’ve probably seen a raised bed made with a single layer of landscaping timbers, which are only 3.5 inches tall. A shallow bed can stunt your plant’s growth, especially if your raised bed has compacted ground underneath it. They also seem to magically grow grass.
A bed deep enough to allow eight inches of soil is about the minimum for healthy plants. While some crops, like strawberries, are shallow-rooted, most will enjoy some space to send down roots. You’ll also spend less time watering.
What is the Ideal Size for a Raised Garden Bed?
Many factors combine to delineate the ideal size raised garden bed, which will vary for everyone. Some factors to consider are your intended crop, building materials, space, and integrating the design with the rest of the area.
It’s hard to beat the standard 4’x8’ bed 10 inches deep (2 layers of 2×6 boards) for all-around vegetable versatility.
Veggies, Flowers, Herbs–How Deep Should My Raised Bed Be?
The great news is that pretty much anything can be grown in a raised bed. Consider that when designing–you may be growing kitchen herbs and flowers this year, but potatoes and carrots might be on the plan next spring.
Building raised beds deep enough to allow for crop rotation adds flexibility in the future. Keep bed depth at least eight inches, and twelve is fantastic. Remember, a 2×8 board is only 7.5 inches high when laying on its side, and soil will settle lower than that.
Building Materials and Raised Bed Size
If you are building raised beds out of wood, you’ll have less waste if you take standard lumber dimensions into account. Even a funky hexagonal bed can be designed with two-foot-long sides to use the wood efficiently (three 2×6 boards eight feet long will build a fabulous hexagon raised bed with 2-foot sides and no waste). Design 26-inch long sides, and you’ll need a fourth board and be left with a bunch of scraps.
If using bricks or landscaping blocks, measure their actual size–plus a mortar joint if necessary–and design in multiples of bricks to avoid cutting blocks. A trip to the store with a tape measure and notepad can save frustration later.
Space and Flow
Not only does your bed have to physically fit in the space you have for it, but you’ll also need to plan access. Two feet between raised beds is about the minimum for comfort. You’ll need space to work in and for the wheelbarrow, mower, garden cart, or other items.
Pro Tip: If you’ll have grass between the beds, make sure the mower fits.
While an assortment of random raised beds may look eclectic, that might not be the vibe you’re going for. A long, wide, raised bed can seem to take up all the space in a small yard, even if it doesn’t. Two or three smaller ones can fit the landscape better. Play around with it, marking off spaces with stakes and yarn.
Once you’ve decided on the size, depth, and how many raised beds, use our free soil calculator to learn how much soil you’ll need.
About the Author:
Andy Wilcox is a freelance writer and flower farmer who is passionate about gardening, horticulture, and forestry, and believes healthy soil leads to healthy people. He is a Master Gardener and a member of the Farmer Veteran Coalition of Wisconsin. He can be reached via email: andy@thatgardenwriterguy.com.
