Colorado's Front Range soil is almost universally poor - mostly bentonite clay which, is virtually impossible to dig when it's dry and doesn't allow proper drainage - and makes gardening an act of will. Raised beds offer a relatively easy solution for small scale backyard gardens because you add in the soil of your choice instead of trying to till amendments into the existing ground to make it usable.
There are a ton of different how-tos on the internet on building a raised bed, but these are the ones that stood out to me. Below I have elaborated on the instructions that I thought were most helpful.
This Sunset Magazine one is pretty good, but it's a little over the top (How to Build a Raised Garden - Sunset.com). It's 4ft by 8ft and uses 4x4 posts at the corners that are set into the ground to keep it in place, which is probably not necessary for most small beds.
The Better Homes and Gardens instructions are for a 4ft by 4ft bed that be taken apart (Raised Bed Gardening - How to Build a Raised Bed Garden - BHG.com). The instructions are a little vague, but it's a cool design and would be great for someone who is renting and would like to take it with them when they move.
This video from Lowes (How To Build A Raised Flower Or Garden Bed - YouTube) is probably the simplest and is explained really well. This one is 3ft by 5ft, which is also a nice size for a starter garden.
Basically, all of these instructions involve attaching some longer two-by-somethings to some short 4x4 posts, leveling the ground, setting the frame inside, and filling it with dirt. In the dry Colorado climate you can use plain, untreated lumber instead of treated "green" wood (which you can't grow veggies in because it's poisonous) or expensive, but rot resistant, cedar or redwood. Most people will loose interest in this little raised bed before it rots out in a few years anyway, so you may as well save a few bucks. All of these instructions also enable you to start with readily available 8ft pieces of lumber and not have any waste, which is nice. Depending on your level of handiness or ability to enlist a friend's help and power tools, I would have everything pre-cut at Lowes or Home Depot (or your local lumber yard) to the sizes you want and then follow the instructions in the Lowes video to pre-drill the planks and assemble the box.
Here are the materials you would need to build the 3ft by 5ft raised bed from the video:
- (6) 8ft 2x4s, each cut into 3ft and 5ft lengths at the store
- (4) 10-1/2" lengths of 4x4 post, cut from whatever 4x4 lumber is cheapest (2x4s are not actually 2" by 4" anymore, they're about 1-1/2" by 3-1/2", hence the 10-1/2" posts)
- (1) 1 pound box of 3" deck screws - you'll need at least 48 screws, plus the ones that get messed up in the process
- 6ft of weed barrier cloth
- Aprox. 15 cubic feet (5/8 cubic yard) of garden soil - the bagged stuff is about the actual size it says on the bag, the loose stuff tends to settle down, so you may need a little more; also, you don't need to use all potting soil, just whatever is easy to get
Here are the tools you will probably need:
- Shovel to cut away the grass / sod (or just lay the weed barrier right on top if you've got a dead spot that's already level
- Drill driver (corded or cordless) with a 5/32" drill bit (to drill the pilot holes) and at least one #2 Phillips driver bit (to drive the screws)
- Tape measure (to make sure the box is square, measure the diagonals when attaching the sides and make sure they are the same)
There are no limits on the ways you can modify, expand, or customize your new raised garden, including adding hoops for a makeshift greenhouse or bird netting or attaching it to anchors to keep it from being bumped by the lawnmower.
I hope you enjoy your new garden, and don't trip over it in the winter snow! Maybe next time I'll elaborate on the slightly more complicated one that my family built this spring.