Build a Raised Garden Wicking Bed

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Introduction: Build a Raised Garden Wicking Bed

This raised garden bed was an idea hatched from being part of a Facebook group called "Raised Bed Gardening." I came up with the plan, and members made suggestions for providing side support (preventing the sides from bursting) and creating a wicking bed (reduced watering and encourage root growth).

The reason I made it so high (`30") was to eliminate bending over (50th birthday coming soon), to raise bed to sun light levels (bed was behind garage), and to (hopefully) eliminate rabbits and other critters from invading garden. Why the solar lights? Purely decorative.

If you download google's sketchup program, I have uploaded the plans in the .skp file below for your review.

Additionally, I was provided assistance from the following videos and links:

Step 1: Wood Materials Needed

  • 4 - 2" x 12" x 10' treated lumber (sides)
  • 4 - 2" x 12" x 6' treated lumber (ends)
  • 2 - 2" x 6" x 12' treated lumber (sides)
  • 2 - 2" x 6" x 8' treated lumber (ends)
  • 2 - 2" x 8" x 12' treated lumber (side tops)
  • 2 - 2" x 8" x 8' treated lumber (end tops)
  • 3 - 2" x 4" x 8' lumber (inside braces)
  • 2 - 4" x 4" x 8' lumber (posts)
  • 4 - 2" x 4" x 8' lumber (outside braces -- these will be cut in half to make the 8 pieces required)

Yes, I used treated lumber. Lots of debate on this on the interwebs. However, more recent posts have indicated that the new treated lumber is safe for use as a planter or garden bed. Additionally, I will be lining the inside with plastic, so the wood will not come in contact with the soil. Besides the wood is cheaper, and will last longer.

FYI - I called the sides the longer sections (10') and the ends the short sections (6').

Step 2: Non Wood Materials Needed

  • 2-3 tons of pea gravel
  • 2.2 cubic yards of black dirt

  • 1 1/2 gallons stain (outside only)
  • 10' x 20' Heavy Duty Water Resistant Blue Tarp (Don't use the 4 or 6 mil plastic --- it will leak)
  • 4" PVC black tee to use with corrigated drianage pipe
  • 4" x 30" PVC pipe
  • 30-40' 4" drainage pipe (for wicking bed)
  • 2" x 2' PVC pipe (spill over)
  • 3 tubes wood/cement crack sealer (to seal all boards)
  • Wood putty (for top railing)
  • 3" deck screws -- get a box (e.g., 300)
  • 4 - 4" x 4" solar post caps
  • Paint supplies (rollers, brushes, etc)
  • Drainage Pipe Sock (to prevent soil from clogging the drainage holes)
  • 4' x 50' Ground Cloth (to line the bottom of the bed to prevent puncturing the tarp, and on top of the gravel to separate the soil from the gravel)

Step 3: Tools Needed

  • Sawsall
  • Circular Saw
  • Triangle
  • Level
  • Cordless Drill
  • 2 1/4" Drill Saw/Bit
  • Shovel
  • Rototiller
  • Staple Gun

Step 4: Prep the Wood

The stain I used required two coats. I decided to apply the first coat to the outsides of the boards, as it would be hard to stain some areas once assembled. I also pre-drilled the screws into the boards in a symmetrical pattern to eliminate guessing during assembly.

I made the end pieces screw into the sides as well as the posts, and the side pieces screw into the posts only.

Step 5: Level Ground

Make sure where you are going to place the garden bed is level. Here we used bricks to ensure that the ground was level, and used loose dirt to fill in the bottom of the bed.

Step 6: Make Sure Everything Is Square and Level!

Use a square to make sure things are at a 90 degree angle, and use your level to make sure your boards are level to the ground and with each other.

Step 7: Assemble Sides, Ends, and Posts

Using pre-drilled sides and ends, screw into each other and the posts.

The 12" boards will make bottom sides and ends, while the 6" boards will make the entire bed 30" high -- table height.

Step 8: Inside Braces

Install the inside braces. Use the 2" x 4" x 8' boards for the sides, and cut the 8' board into two 4' boards for the ends.

Step 9: Outside Braces

You should have 8 - 2" x 4" x 4' boards with the ends cut at 45 degree angles so that you can pound them into the ground. Three of these will be evenly placed on each side, and one placed on each end.

Step 10: Cut Outside Braces

Once you have pounded the braces as far as they will go, use a sawsall to level the braces with the sides.

Step 11: Seal the Wood

Not sure this was totally necessary, but I saw that others had done this in their raised garden beds. I used crack filler to fill the seams between the bottom two boards.

Step 12: Install Spill Over Pipe

To prevent the garden bed becoming a bog, I installed a spill over pipe directly over the first board. I used a 2 1/4" saw/drill bit to make the hole. The 2" x 2' PVC pipe was actually 2 1/2" in diameter, so I had to use the sawsall to make the hole larger. Once installed, I used the crack filler to seal the edges around the pipe.

I drilled 3/4" holes around the pipe to aid in draining the bed.

On the inside end of the PVC pipe, I used drainage cloth and a clamp to prevent soil or gravel from leaking out or clogging the pipe.

Step 13: Install Top Railing

I thought I would install a top railing to make it more decorative. This required longer boards to fit over the 10' and 6' boards. I cut the ends at a 45 degree angle, and then made a 3 5/8" notch on each end. Once married with the other railing, this notch would surround the post. I used shims and wood putty to make everything flush and even.

Once all the railings were cut, I applied the first coat of stain before installing them to the sides and ends.

Step 14: Assemble Drainage Pipe

I used about 20 feet of drainage pipe (corrugated, black 4" pipe with holes in it) and put a drainage sock around it to prevent it from clogging. Then I attached it to a black tee (don't use the white PVC tee, it won't work). Then I attached it to a 30" white PVC (4" diameter) tube, that I would use to water the wicking bed.

My son came up with a great idea of tying the center together to prevent all the water from pooling to the sides of the bed.

Step 15: OMG -- Test the Water Bed BEFORE Putting the Gravel In!

Don't use the 4 mil or 6 mil black plastic -- this stuff leaks! Use a heavy duty blue tarp. I found the hard way after moving 4 tons of gravel into the bed, that it leaked. I had to shovel it all out, and start again. Unfortunately, the bed continued to leak at the spot of the spill over pipe, no matter how much I caulked it -- so make your spill over at the exact height you want water to be.

Once fully tested, and you can prove to yourself that the wicking bed will hold water for days, then you can fill it with gravel. I placed cardboard underneath the tarp to prevent anything from the ground puncturing the tarp, and lined the top of the tarp with ground cloth to prevent the gravel from puncturing it. I also filled the bed with water before moving the gravel in, to prevent the gravel from puncturing the tarp when I shoveled it in.

Test the wicking bed again, before putting the soil in. If it leaks, you need to start over again. It's a wicking bed, dummy -- not a leaking bed!

Finally, cover the top of the gravel with ground cloth to prevent the soil from clogging up the drainage pipe.

Step 16: Add Soil and Plant!

I put composted leaf mulch in first (from our composting bin), and added top soil on top. I screwed in cup hooks every foot on the outside of the bed. Then, using twine I was able to create a grid for square foot gardening.

You can plant anything. Here's what I did:

  • Marigolds line the perimeter.
  • Broccoli down the middle.
  • On the right are herbs -- dill, rosemary, Greek oregano, Italian oregano, cilantro, and basil.
  • On the left -- Serrano peppers, green peppers, roma tomatoes, and grape tomatoes.

I have to the bed another coat of paint, and sand down those filled in cracks. I had a ton (literally) of extra pea gravel that I am going to use to create a walkway around the bed. I will post pictures later this summer to show the growth of the garden and the final, final finished product.

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24 Comments

I just don't get the point of the liner and overflow. It's like building a bog.

You're building this bed over dirt, right? So why bother. Let it just drain down into the dirt.

I like the design and will borrow parts when I put in my raised bed gardens. But I'm just going to use drip lines on timers for watering. It what the plants don't use will just drain down into the soil below if it gets that far. The only thing I'm putting on the bottom is a weed barrier.

I, too, am over 50 and want something raised, albeit not this much, with a nice railing to sit on. I like the solar lights. Hadn't thought of that but might incorporate it. The only critters I'm worried about is neighbors stealing my crops just before harvest.

The idea is that this garden is designed to be a self-wicking design like the Earthbox, but on a larger scale. If you're not familiar with self-wicking/self-watering beds, check them out. They are efficient and the plants get the water as they need them. The overflow prevents it from becoming a bed of mud, and the soil above the water reservoir uses capillary action to wick the water from the base up to the plants' root level.

I have grown in Earthboxes since they were first shown at the Epcot Flower and Garden show in 1990-91. They are the perfect gardening system for someone who doesn't have the time or inclination to spend watering, weeding and otherwise caring for a garden, or for those severely limited in space, like on a balcony, porch or patio. I am thrilled to see this design because I now have 4 teenage grandchildren clambering for corn on the cob. It would take a lot of Earthboxes to supply that bunch with enough corn. I am downloading and printing everything and hopefully, will be able to talk my son into building one of your boxes specifically for growing corn.

And a side note... unless you are used to the Earthbox, there is something less than beautiful in the sight of 8 or so all lined up across the garden area. Your design is considerably more attractive, especially with those solar lights. Gotta get me some of those!

<Besides the wood is cheaper, > Cheaper? than what? Untreated?

Cheaper than cedar, or cedar simulated. They didn't have any pine untreated for some of the boards I needed.

What is simulated cedar? The best outdoor woods are teak, cedar, cypress, redwood.. Worst might be maple.

About all I would consider changing is 4 ft wide rather then 6 ft. That way you can reach all the plants without crawling into the bed. Thanks for the ible.

Lol, my father in law said the same thing. However, I planted broccoli
in the middle, which doesn't require much attention. The tomatoes and
herbs surround the edges of the bed, so they are easily reached. I can
touch the center with a little leaning, so it wasn't as big of a deal
as you and my father in law think :).

Your raised bed is definitely the "Cadillac" model...
I wanted to offer an alternate idea to the solution to the bowing problem without spikes into dirt. Once you put wood supports in dirt, it's over. They'll all break at the ground line eventually and then you'll loose all of your bowing solution.
I did mine as completely free standing. In the middle of each of the long sides I added 4X4 vertical supports on the inside. I attached these to each other with a 2X4 parallel to the short sides (and ground) and about two inches below the level of the dirt so it would stay hidden (also wood in dirt that will rot). I used heart redwood all around. Now this bowing support will rot at about the same rate as the rest of the bed and I can easily replace it if it ever gets really bad.

I did the stakes and the braces on the inside. I see your point about the stakes eventually rotting, but I think the inside braces will hold.