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Raised Wicking Bed

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Project by McPheel posted 12-27-2016 02:01 PM 1179 views 8 times favorited 3 comments Add to Favorites Watch

Another utility project that turned out better than I expected. This goes beyond just wood working so read on if you like but be forewarned.

Las May, I got the go ahead from my wife to build this large wicking bed (8’ x 8’ x 3’). The design is simple enough and resembles a typical raised bed planter but with one very important twist. This planter will be self sufficient not requiring constant watering and increasing the efficiency of of the plants nutrient uptake and root strength.

I initially had big dreams for the joinery of the box with lots of mortise and tenon joinery and tong and groove to lock it together. In the end, due to many other projects on the go and my wife always bugging me about over complicating what typically would be a simple project (a lot of truth there), I ended up just using pocket hole joinery to join the corners and the layers together. I did add one bonus feature with a bench in the back that was installed using mortise and tenons and a tong and grove along the back. Although the project was an outdoor backyard project and built with treated lumber, i still sanded every piece to be smooth and hit it with a light coat of linseed oil.

Now the twist on the project. This is a wicking bed which is also referred to as a SIP (Sub Irrigated Planter). I highly recommend looking up the details online if your interested but here is a general overview of how it works. You make your box water tight so that a reservoir of water can be created at the bottom, on top of this reservoir is your soil which you propagate your plants in just like normal. What happens is the water will be used as needed by the plants and will not evaporate in the sun like surface watering. As the plants grow, the roots become very strong as they reach down and spread out in search of water which is slowly wicked up into the soil through capillary action and absorbed by the plants.

Here is how I did this: I used a thick builders poly and with much difficulty, wrapped it around the U shaped planter. I ended up having to divide the planter into three separate reservoirs due to the difficulty of doing a continuous wrap. the reservoirs were joined together by a small 3/4” PVC pipe so the water levels always balance. The back reservoir had a small bucket at the intake point that houses a float valve, as the water level lowers, the float valve engages a pump that draws nutrient rich rain water from another garden system in my yard (aquaponics). I never have to physically top up the beds. I use an upright pipe for each reservoir that can be used to top up the reservoirs but mostly in my case just ventilates them so the water doesn’t go anaerobic and become rancid.

Through some experimentation i found that in the reservoir, instead of using washed rock like many people do, the wicking was more efficient if i used sand. The base is filled with 5 mm masonry sand which allows the water to wick up, this does reduce the volume so to counter that I used pieces of weeping tile pipe to gain water volume. I then apply landscape fabric over the sand and drill overflow holes at this level. This keeps the soil from mixing with the sand and also allows water to escape so the plants are never flooded in a rain storm. I added a nutrient rich soil mixture on top of the fabric and at this point we were done. planting began and as you can see, we were hugely successful with this concept and design. We even found that bugs were not much of an issue which we assumed was due to the lack of surface moisture.

This is a fun summer project and my wife and I put a lot of literal blood sweat and tears into it as she personally hauled truckloads of sand while i was at work to fill it up and we both struggled to make the bed water tight resulting in a few stitches for myself (Read about my accident here).

-- Never half-ass two things. Whole-ass one thing - Nick Offerman





3 comments so far

View LJRay's profile

LJRay

97 posts in 1168 days


#1 posted 12-28-2016 05:44 AM

The Family Handy Man had an article on a smaller version of it. One day I’ll make one. :)
Thanks for posting it and your tips.

-- Ray

View scatruler's profile

scatruler

27 posts in 211 days


#2 posted 12-29-2016 12:25 PM

cool

View JCinVA's profile

JCinVA

148 posts in 494 days


#3 posted 01-13-2017 08:56 PM

This was on the list for this spring, and your ideas will improve the design I have. Thanks for sharing.

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