A friend came to me this spring and asked about starting a vegetable garden. She had a sense of urgency, which you cannot have in our heavy clay soils, which take years to improve with compost and crops. I suggested she build raised beds to fill with the perfect growing mix if she wanted fresh organic produce this year.
Planning a raised bed garden
There are many options for raised beds, and you can do them all yourself. I have dug a rectangle shape down about 4-6” and placed large rocks around the perimeter, filling it in with good soil for planting. The soil that was removed was scattered in the far reaches of the yard.
I have used scrap 1’x12’ lumber to build a frame that is, obviously, a foot high. This is another good scenario to dig out soil a bit where you want to place the raised bed. It does two things – connects your garden to the existing soil and gives you a bit more depth and drainage. You don’t need depth for shallow rooted plants, like lettuce, but for root crops, like beets and carrots, the deeper the better.
A raised bed of wood should be redwood or cedar, which are naturally rot-resistant. Wood used in any project should be sustainably harvested. Look for verification labels, and ask about sources at the lumberyard. It will take some footwork to find reclaimed redwood or cedar, but it would be well worth the effort. Recycling is eco-friendly!
Materials to avoid for your raised bed garden
Do NOT use ‘pressure treated’ wood. EVER. It is treated with toxic elements, such as copper and arsenic, which leech into and permanently contaminate your soil. The extra cost of redwood or cedar is definitely worth avoiding the health risks. The other option is to treat plain (sustainably harvested) wood with linseed oil, and replace it more often.
There are kits to make raised beds, too. These are often recycled plastic, and I don’t recommend them. This ‘plastic lumber’ is still plastic that takes a lot of energy to produce, but my biggest beef is that it never decomposes! It is durable, does not rot or warp, and lasts a long time, which, obviously, makes it attractive to a homeowner, but it will never rot back into the ground like wood does. It will persist in the environment like all plastic. Please don’t use it.
Make your raised bed accessible
Once you have decided on your materials, decide on where to locate your raised bed, or beds. They need at least six hours of direct sun a day. They should also be handy to the house and water.
You need to be able to work comfortably in a raised bed, which means you have to be able to reach the center of it from each side. You won’t be stepping in it, so all crops have to be easily accessed. I recommend a 4’ width, but it can be as long as you want, but not so long you waste time walking around it. A series of shorter beds in a pleasing pattern is more efficient.
Now that you know the size and location, draw it out on paper. If you want to build more than one, come up with a workable plan with room for movement and tools. You’ll want to be able to get a wheelbarrow in between them, and you’ll need space for walking, bending and hauling materials.
Build the garden bed frame
Build your frame. You need 1”x12” or 2”x12” lumber cut to length, corner braces, and posts to secure it into the ground. The thickness of your lumber will depend on the size of your bed. The bigger it is, the larger the lumber should be for stability.
Attach the ends to the sides with your corner braces. These can be metal braces you get at the hardware store, or you can buy 2”x2” lumber for this. If that’s the route you take, make those posts double as the stakes that go into the ground. You would want to cut them the height of your raised bed plus another 8” to sink into the ground.
If you want your bed to be 2’ high, you will have to stack your lumber two high, and place the posts at regular intervals, attaching the upper and lower boards to them. The corner posts are the only stakes that will go into the ground.
Next, mark the beds with stakes and string. The size will be the inside of your frame, which will sit on the existing land. If you have sod, cut the sod out, and put it aside. Dig down a couple of inches, then put the sod in upside down. The grass will decompose and add valuable nutrients to your garden. The frame will sit on top of the existing land outside of this shallow dug area. Once it’s in place, secure it into the ground. Your stakes should be sitting inside the corners.
Now it’s time to fill it with soil! The beauty of a raised bed is that you can have the perfect growing mix without having to amend your own soil.
A typical soil mix for container gardening can be used in a raised bed, because it is basically a huge container. The mix needs to be able to retain water, yet have good drainage, and it needs the proper nutrients. Cornell devised a mix of three parts – 1/3 topsoil (nutrients), 1/3 compost (nutrients and drainage), 1/3 sand (drainage). There are alternatives to each of these, but that is an entirely different subject. Google would be your friend for that, or you can ask at a nursery that sells bulk soil and compost. You can also call your county extension agent for information.
The last step is to plant, harvest and enjoy your hard work!