1 way to build a wicking garden bed

Before and after
Wicking garden bed illustration
Wicking garden bed cross section

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Layout design for 8 wicking garden beds
Layout design for 8 wicking garden beds

Building wicking garden beds was a new thing for me. The idea of this self- contained raised bed is that it saves a lot of water through capillary action by supplying water from the bottom up.

Some of the benefits of wicking garden bed:

  • It prevents evaporation
  • self-watering
  • drainage during heavy rains
  • tree roots don’t reach soil

The timber for the garden beds was ordered from Dovetail Timber in Tasmania. Very solid 250 x 160 cm frames stacked together reached 60cm of height.

For this wicking garden bed plan I simply leveled the surface of the ground with a shovel.

Outlining and leveling each garden bed
Frames for the garden beds from Dovetail Timbers
Had to grind half a dozen stumps. Hands vibrated for a while afterwards.
Tools of choice
Protection for the Timber. Gives a nice colour and probably few extra years.

Apply protective coating for the wicking garden bed frames with protective oil (Description of Intergrain Nature’s Timber Oil).

Protection for the parts of the timber that are underground
Apply 1-2 coatings for the parts of the timber that are underground

The parts of timber that are against and under the ground a stronger protection was used. (Description of Diggers Eco in-ground Timber Protecta)

Project underway

Before you start applying coating to vertical corner post remember to round the sharp edges and splinters with f.ex sand paper. This way at the bug nets will stay in better shape for longer.

Painting setup
Bottom layer of timber on leveled ground.
Bottom layer of timber on leveled ground. At this point if you want you can decide which corner will have the overflow for the water reservoir and level the inside ground of the frame leaning slightly towards that corner. This way the water reservoir will get emptier if water is drained. Leave the ground where the actual frames lie in perfect level.
First frame assembled
All frames assembled
Detail shot of the garden beds frames
Tightening corner screws carefully. I recommend using a drill at the end.
Vertical pieces were dug about 10cm deep

Place the wooden poles to each corner and center of the short edges. Screw them to the frame using screws and L-brackets. I dig small holes for the vertical posts and buried them 10cm deep. Stomp the earth tightly around the poles.

Installing the corner posts and the horizontal beam.
2 L-brackets were used to secure the corner posts
Tools for the interior work of the garden beds
Drills needed to make a hole to the garden bed frame
First a bigger hole about 1cm deep

Drill hole to the corner where you wish to have the water outflow of the wicking garden bed. First drill a bigger hole for the plastic nut and then a smaller one for the hollow plastic bolt.

Testing that the hole is deep enough

We found that by placing an extra plastic nut inside the frame the overall pipe system felt more solid. Like any phase of the project there are many ways of doing things. This one seemed like a good idea.

Smaller hole through the garden beds frame

The drill sizes I used were slightly too small so some tweaking was required for the overflow pipe to fit the hole.

Placing the bottom layer of geotextile. (ignore the plastics under the textile. Also no need to bring the bottom layer that high.

Cut pieces of geo-textile large enough to cover the bottom of the frame. I used staple gun to attach the textile to the timber. It made other phases of the project easier to do. The idea  for geo-textile being on the bottom is to protect the water reservoir from getting punctured by small stones or roots etc…

Plastic nut and rubber gasket before placing the water reservoir plastic
Plastic for the water reservoir. Place the plastic container tarp inside the frame. It helps if you measure and draw where the corners more or less should be.

Placing the plastic water container / reservoir takes time and is quite annoying. It helps to draw lines where each side is suppose to go and mark the corners to make this part of the job more straight forward.

Placing the plastic is sometimes tricky
Placing the plastic is sometimes tricky
Pieces for each overlow / emptying system. 1 rubber gasket and plastic nut missing from the photo (the 2 items on the right of the photo).
The emtpying / overflow valve would look something like this
Puncturing a whole to the water reservoir plastic

Cut a hole through the geotextile and plastic tarp so the water outlet reaches the inside of the water container. Clean the gaskets, the plastic and glue everything together. Apply just the right amount of tightness so that everything glues together nicely. Who knows how tight is ´just right´…

100mm SLOTTED(!) drain pipe. 16 meters long fully extended
Geotextile, plastic reservoir, 6mm river pebbles & slotted drain pipes.
After the slotted drain pipe is installed the garden bed is filled with 6mm river pebbles. Roughly 1 cubic meter of river pebbles per bed.

Fill the plastic water reservoir with 6mm river pebbles to the top level of the first long edged timber. Almost a 1m3 of pebbles was used for each wicking garden bed (20cm height).

Try to avoid letting the pebbles fall into the drain pipe and overflow pipe.

Valve to empty the water reservoir and the overflow tube before cutting it to the right length
Sometimes the plastic doesn’t bend nicely around the middle vertical post
Pebbles filled to the top of the first crack of the garden bed frame (20cm deep). Lacks leveling.

Cut the excessive plastic away and level the pebbles.

Install a new layer of geo-textile on top of the pebbles. Try to cover all the spaces between timbers. This way the soil will not accumulate so easy between the timber. I used quite a few staples to put the geo-textile nicely. You can also use short nails.

Cutting geotextile
Using staple gun to secure the geotextile to the beds (optional).

 

This layer of geotextile is to separate the pebbles from the soil. Ready for soil.
Filling material: Coir Power. 1-2 per bed.
Coir after and during a good soak
Filling material: about 1 bail of hay per bed. Filling also included half a bail of rotten hay per bed.
Filling material: 1 cubic meter of Mushroom compost per bed.

I filled the frames with fresh and old hay, mushroom compost (1m3), soil that was removed while leveling the ground, old chicken poop soil and coir. What is your weapon of choice?

8 ready assembled wicking garden beds
8 ready assembled wicking garden beds
8 ready assembled wicking garden beds
After the project was done

Soil mixture
Wicking garden bed filled with soil
Eat well!
Have fun!

If you have any questions of comments you can write on the ‘comments’ section.