With the prices of fruit and veggies these days and the dubious stories about food tampering we’ve put together an easy guide to planting your own planter box.
When we say “raised garden bed” or simply “raised bed,” we’re referring to a freestanding box or frame—traditionally with no bottom or top—that sits aboveground in a sunny spot filled with good-quality soil. Raised beds are usually open on the bottom so the plant roots can access soil nutrients below ground level.
Of course, a raised bed can be even simpler than that: you could build a raised bed without a frame, mound the soil 6 to 8 inches high, and flatten the top. This requires no additional materials (beyond soil).
Consider what you may grow. The depth of the soil itself is very important and depends on how much soil depth the crop needs belowground. For example:
Deep-rooted crops such as carrots, parsnips, potatoes, tomatoes, and squash need a minimum soil depth of 12 to 18 inches. Without loose soil to this depth, the roots will not be able to access nutrients.
Shallow-rooted crops (like lettuce, greens, and onions) need a minimum soil depth of 6 inches.
To place it safe, you could just ensure your beds have a depth of 12 to 18 inches. Whatever height you choose for your frame, you’ll need to loosen the soil below the ground accordingly. For example, if you have a bed that’s 6 inches high, we recommend loosening the soil below the ground about 6 to 9 inches if you wish to grow root vegetables. If you are only growing shallow-rooted crops, there’s no need.
Where to Put Raised Beds: The Best Location
Raised beds need to be in sites with lots of sun! Here are the requirements:
Most vegetables need 6 to 8 hours of direct sunlight daily (“full sun”), especially from lunchtime onwards.
Level, even ground.
Close to the house for easy access to weeding and harvesting
Do not site your bed in a windy location or a frost pocket.
Soil needs to drain well, so avoid any wet or marshy areas.
Preparing the Site: Option 1 (Basic)
To make a basic raised bed, outline the spot where you want it with string. As mentioned above, keep it between 3 to 4 feet wide so you can still reach the center easily.
It helps to have smothered the grass in the area, but if there is sod or grass in place, mow it short and dig it out, saving the clumps to one side.
Loosen the soil in the bed, flip the clumps of sod upside down in the bed, scrape soil from the pathway around the outside, and add that to the bed, along with any other amendments you wish to use to raise the level of the soil.
You can quit right here if you want.
Preparing the Site: Option 2 (No-Dig)
Some gardeners don’t bother digging out the turf, as the soil will block out the grass and weeds beneath it as long as it’s a thick enough layer. Gardener Charles Dowding founded the “no-dig” method. His philosophy is that digging brings more weed seeds to the soil surface, leading to more weeds and more weeding. Digging also hastens nutrient loss, so you’ll need to feed plants more often, and it rips apart the complex life and very fabric of your soil, reducing its ability to drain properly and retain moisture.
Here’s how to build a raised bed using a “no dig” method:
Mow the grass or weeds as close to the ground as possible. Then, cover the area with cardboard, smothering the grass/weeds, and eventually rot down into the soil. (Make sure you pick off any tape and staples that won’t decompose.)
Be sure to overlap the cardboard/newspaper (by about 6 inches) to ensure no weeds slip through cracks. They will reach for any sunlight they can find.
Add a thick layer (4 to 6 inches) of compost on the top of the cardboard. This will be your growing medium.
It’s fine to get on and plant immediately after setting up. By the time the roots reach the cardboard, they will have started to break down, and they will be able to search deeper beyond that cardboard layer.
The compost you add on top should gradually become incorporated with the soil beneath through the actions of worms, etc. Beds will need topping up with fresh organic matter (an inch or two) each fall/winter, which will help to gradually improve the fertility and health of the soil, including that below the level of the raised bed. This means you should be fine growing deeper-rooted veggies like root crops.
For Those With Compacted or Bad Soil
Digging below the ground is often necessary in soils damaged by compaction or other problems, but it only needs to be done once. This is most important for deep-rooted crops such as carrots, which do better in soil that has been loosened and amended down to 10 to 12 inches to allow air and water to reach the plants’ roots.
After mowing the grass short and digging it out, remove the top layer (about a shovel’s depth or 10 inches); it may be easiest to work in rows.
Remove all rocks, old roots, and plant debris.
Dig down a little further with the shovel (a few more inches) to just loosen up the soil.
Mix the soil with organic matter such as compost. We recommend that the compost make up about 25% of your soil.
Then, return the top layer and mix the soil layers together.
How to Build Your Garden Bed!
Let’s make a bed! You are simply building a box—like a sandbox—requiring minimal DIY skills. It’s fine to buy a commercial raised garden kit, but they can have cringe-worthy prices.
Tools
Drill/driver and bits, screwdriver
If cutting the planks yourself (vs. lumber store): Hand saw, tape measure
Materials
For a 4x8 foot bed, get 3 pieces of 8-foot long 2”x6” lumber. If they have 2”x8” or 2”x10” lumber, even better. For a 4x4 bed, get 2 pieces of lumber.
If you don’t have a saw, ask the guys at the lumber yard to cut the pieces in half. For the 4x8 foot bed, they will cut one of the pieces in half for you, giving you two 4 foot lengths to use for the ends. For the 4x4 bed, they will cut both pieces in half.
Deck/exterior screws
To make it stronger, use a piece of 2X4 or 4X4 in the corners to give you something stable to nail or screw into rather than the end grain of the board.
Fill your beds all the way up! The soil will settle, especially with watering. As it settles, you can always top off with compost.
Filling a Raised Bed
The most important part of any garden is the soil, and the more organic matter it contains, the better. Soil microbes are fed, oxygen and water readily reach roots, and plants thrive. Here is the balance to aim for:
40% compost: Compost is packed with nutrients for plants. While you can compost at home, it can also be purchased in bags from your local garden center. Aged manure can also be used, but you can NOT put fresh manure directly in your garden. Learn more about manure.
40% topsoil: We’re not talking about “potting soil,” as it’s too fluffy for raised beds. You’ll also find bagged topsoil at a garden center, local farm supply, or lumber store.
20% aeration: In terms of aeration, many bagged soil mixes already contain some perlite, pumice, or rice hulls. If not, you need to add something for drainage. Lava rock is also a good aerator for drainage.
If you are filling a lot of raised beds, we’d recommend that you look into a local landscape company to build soil and compost mixes, which should be cheaper. But if you’re filling up a small bed, bagged is the way to go.
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