Build a Raised Garden Wicking Bed




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 Discussions

    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.

    2 replies

    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?

    2 replies

    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.

    1 reply

    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.

    1 reply

    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.

    Very nicely done and looks great. Nice addition to your yard. I was most interested in this Wicking Bed idea and so read through your instructions in detail. I also really appreciated your references at the beginning that sighted videos and links. After reading the link: Sustainable Gardening Australia by Helen Tuton, it was explained in there about the wicking action.

    My concern is that you may have a "potential issue" with your bed so please be aware of this, IF you have any issues (hopefully not). The article talked about the research that showed that the maximum depth that the "wicking" works on is 300mm or about 11 3/4 inches. In that top layer of soil it appears to me that you used a 2x12 and 2x6 boards, which is approximately 16 1/2 inches (11 1/4 +5 1/4). This may not be an issue but if you have trouble with the soil wicking, you may have about 4 3/4 inches too much soil. If this seems to be a problem, just scoup out 4-5 inches of soil next spring and replant.

    The other issue I had was that the same article talked about laying in over the landscaping fabric a "good quality water retentive soil" for about 150mm or about 6 inches. I am not sure what a good quality water retentive soil is but I am not sure that composted leaf mulch is what they mean, but I may well be wrong. If someone knows please enlighten us all. I think the leaf mulch would allow the water to drain down faster than retaining it to be wicked upward. My thought is a soil that has been amended but still has a fair amount of clay in it, which slows the percolation of water through the soil would be more of a water retentive soil. Again, may be a minutia point but just thought I would mention it.

    You went to a lot of work making this project and did a great job. And I really do hope it works as you wish. If you have some problems with dry soil and lack of wicking, I just wanted to mention the above as possible issues that could be resolved to give you a successful Wicking Bed.

    1 reply

    Thanks for your comments. I was aware of the soil only wicking up 11 inches. The first 12-14 inches is gravel and the water bed. The soil is only 12 inches deep. I used leaf mulch and top soil, and it is working quite well. In fact, the garden is thriving and looking for a huge harvest in a couple of weeks.

    Another way to conserve water is by using a product called "soil moist". I bought it to use in our garden, but now I cannot find where it is at! Things got moved around and now it is not where it is supposed to be at! lol You mix a certain amount in with your soil and when you water the granules with store the water and then slowly release the water back into the soil for the plants to use.

    Here is the link for soil moist:

    As for your design, I never thought about doing a "self watering" style raised bed planter. I was going to do a raised bed planter until I had to have back surgery in April. So I had to postpone building it. I might incorporate a couple of your ideas in with my idea for a raised bed planter. My idea and on others I have seen use either 1/4" x1/4" hardware mesh or 1/2" x 1/2" hardware mesh on the bottom to prevent moles and other "digging" creatures from digging up into the raised bed. Then lining the bed with "weed barrier" cloth to prevent weeds and grass from growing up through from below. then filling it with a quality "potting mix" or making your own mix to fill the bed.

    Some people use "weeper" hoses, other use drip irrigation, others use other methods such as using old soda bottles or plastic milk bottles with small holes drilled/poked in the bottom (about 1/16" sized holes), bury the soda bottle/milk carton about half way to 3/4 into the soil, and then slowly fill the soda bottle/milk carton full with a garden hose so the water does not rush out and wash away the soil beneath the soda bottle/milk carton. The water will slowly drain out into the soil and will then be near the plants roots. Also the plants will send their roots deeper because the water is at a deeper level than when watering from above with soaker hoses or with drip irrigation. There are products out there that you can just fill up a soda bottle screw on the product and then turn the bottle upside down and push the bottle into the soil and will do basically the same thing. But you risk having the little holes clog up with dirt/soil.

    Yours looks great, I never even thought of using solar lights! Like others have mentioned you could add supports for a hoop system for extending your growing season, or for a trellis system for plants that grow larger and need support like Tomatoes, Pole Beans, Cucumbers, etc. Or you can make the next one with different levels for different plants that grow to different heights! Example a lower level for tomatoes because they grow tall, next level up for peppers, and then another level for leaf lettuce or radishes.

    Keep up the good work!!

    This bed looks great. Have you considered adding a frame over the bed to both tie you tomatoes support and to lay plastic over to form a mini green house for planting early. Also the plastic over it will raise humidity for you plants and make them grow even bigger. :)

    I am a bit concerned with the use of treated wood though they way you have done it shouldn't be a huge cause for concern. Me, I would be more likely to use Western Red Cedar. I used a bunch of reject cedar to build a composting system about 25 years ago and only now am I going to have to start replacing it. I love raise beds as it saves the back and the knees. Your system is a great way to conserve water. Nice instructable.

    This is a beautiful instructable!!!! Thank you! I would love to not be a slave to watering. I hate having to ask someone to water while we are away. Everything I read/observe about most veggie growing is consistency in watering is crucial, so I am the watering slave and I'm sadly not as consistent as I should be. I have 4 counter height raised beds and they are more productive than I could have ever imagined! We barely have any land so I don't have all the beds close to each other and a drip system isn't feasible in our setup. There is something to be said for square foot gardening when there is literally no weeding. Seriously, I have not had to weed in 2 years! All I needed to do was to follow the very easy soil instructions for Mel's mix. Good soil makes tastier vegies. I would LOVE to follow this SIP example when it's time for bed #5. You get what you pay for.... Mel's mix and even, easy watering is a dream come true for me! Thank you again!!!! :)

    1 - You really don't need all that volume.. the water will not wick up rock. 2-3 inches of gravel, then compost/topsoil would have been far better and easier/cheaper to build.

    2 - Since you're dumping water into gravel and not soil, you don't need the fancy tubing setup. Just dump water into one end and it'll self-level throughout the gravel. A simple end capped with holes drilled throughout would have sufficed.

    I think I'll just stick to my old fashioned dirt garden. It takes a bit more work but it is satisfying. I put the cukes, tomatoes, peppers, zucchini, eggplant, grape tomatoes, and plumb tomatoes on black mulch and put the green and yellow beans, red beets and rutabagas on plain old tilled soil. I put the cukes on a trellis and "stake" the others on the mulch, except the zucchinis. I only have to weed the beans, beets and rutabagas. I water them about two to three times a week, as needed. ROI? I don't know, but it sure is productive and I get a lot of enjoyment out of it. Have several plastic tubs with thyme, parsley, oregano and others herbs on the side of the garden. This all inside a fenced area about 25' x 30'....keeps the rabbits and other critters out. Did have to shoot a groundhog with the pellet gun though. He learned to climb over the fence, too bad......Well, it's time to tie up the tomatoes!

    ROI= return on investment. Quality of heirloom tomatoes is beyond numbers. Beans, potatoes, and carrots not an economical choice; but crops that are otherwise expensive or hard to find, like parsnips, beets, shallots, and exotic peppers are good.

    Tbere's a book called "The $50.00 Tomatoe" - or something close to that. Poin is, that gardening requires a sizeable investment and the ROI is not measured in dollars. A point lost in today's finance-centric philosopby?