This article is to describe the process I went through to build my first two wicking beds near the kitchen.
The frame of the first of two beds near the kitchen. Each bed is 2.4m x 90cm. The colourful base is just a protector before putting in the pond liner. This affords extra protection from puncture through the bottom.
The frame is made from permapine timber each piece 200mm x 50mm H4. Length is 2.4m x width 90cm. I made two similar frames and placed one on top of the other to give an overall depth of 400mm then tied them together with 70mm x 45mm soldiers in the corner and screwed them together with tek screws. This gives you a pretty solid box which open at the top and bottom.
It is important to have the structure level so use a spirit level to set them up before going any further. Once level make sure there are no sharp objects on the floor such as stones and twigs that could pierce the pond liner once it is filled with soil. In this photo you will see a colourful material that is actually a failed blow up pool which I cut up to lay flat and give that extra bit of security.
Once this stage is finished it is time for the overflow and pond liner. I used only good quality pond liner instead of black builders plastic because it is thicker and stronger and will last longer. In my smaller barrels I have used black plastic because they are much easier to empty and replace but these beds hold about 1 tonne of soil mix and I want them to last as long as possible. The only area that is important to keep watertight is the bottom and sides up to the overflow.
Pond liner installed in frame and socked agricultural drainage pipe in place.
Before locking in the liner drill a hole about 25mm in diameter that you can use to fit the overflow. In this bed I used tank fittings which are 25mm in diameter and come with back nuts and rubber washers to make it waterproof. Position the bottom of these just above the reservoir which is made of 100mm socked agricultural drainage pipe. Make sure that the overflow fitting goes snugly through the pond liner and tighten the lot to make it watertight. There is no water pressure involved in this so firm is good enough on a nice flat surface.
In the next stage I used a staple gun to hold the liner in place while the rest of the process was carried out. Once pegged to the wall make sure there is plenty of slack in the bottom so that the weight of water and soil does not tear the liner as it settles.
Next you need to install the reservoir. I used socked 100mm agricultural drainage pipe. This is slotted drainage pipe you can buy from agricultural suppliers or plumbing outlets. It comes either bare or socked with geotextile. I prefer the geotextile socked type because the roots will not grow into it and clog up the reservoir but if you want to save money then others use weed mat above the reservoir to hold back the roots. This layer needs to allow the tracking of water but hopefully keep the roots above it and keep the garden soil apart from the wicking sand.
To install the reservoir pipe you will need about 10 metres of this pipe for a bed such as this. Pull the sock over each end and seal with a string or cable tie.Install the fill pipe which will come up the inside of the box above the top so you can fill the reservoir. Cut the bottom of the filler at 45 degree angle then cut a small slot in the ag pipe and pull the sock over the junction and cable tie in place. I also secured the filler at the top to the inside of the frame to prevent it getting accidentally pulled out of the pipe which would mean digging it all out again.
Once done some of the pipe will want to sit up a bit but you need it level on the bottom to get the most water holding capacity. No need for anything drastic but it is time to fill the gaps and loops with building sand or similar with no organic matter that can break down. When adding the sand use shovel loads of it to hold the pipe in place then continue filling until all spaces filled and you have covered the pipe and overflow to a depth of at least 30mm all over.
At this point you can test the system by filling the reservoir through the fill pipe until water runs out of the overflow. At this stage, if you have levelled the wicking sand evenly you will see a small film of water above the sand and the overflow running. Stop filling and go to the next step.
Wicking frame with reservoir installed and sand put in and levelled. You can see the filler pipe in the front left corner coming above the top of the bed.
You need to put some sort of barrier between the wicking sand and the garden or potting mix. I use sugar can mulch which is very effective but others have used weed matting, either way it must let the water through effectively.
Garden soil filled to the top of the bed. Excess pond liner trimmed to the top of the bed and this will prevent any wood preservative from leaching into the bed.
On top of the barrier put about 30cm of potting mix or soil followed by a layer of mulch and job done.
The top of each side is capped with board to tidy up the job. These are recycled boards and give a ledge to sit on or put tools and things. Still to be repainted. Filler tube can be seen above this cap.
Because this is a kitchen garden I want to be able to go out to the garden and not get dirty picking herbs and such. Therefore I dug down 80mm around the beds, put in weed mat and back filled with 50mm white marble. On the right side I will putting some extra wicking barrels to use the space well but no walking over any muddy paths.
The same treatment between the twin beds as on the outside.
Gravel laid down and caps painted. Just a matter of mulching and planting up over the next couple of weeks. The 50mm gravel seemed it could be difficult to walk on but it is great and no problem with the added advantage over small gravel that get stuck in boot treads and carried indoors.
Bed mulched and planted with some test seedlings. In this bed there is lettuce, broccoli green dragon and afro parsley. Don’t forget to water these in at the start to remove air around the roots. I watered morning and night for the first day then the following morning and let the wicking take care of them after that. Working great after 4 days and some very high temperatures around 39c.
Hot weather continuing so needed to arrange some sort of protection for the seedlings. This is insect proof netting which stops butterflies laying eggs on broccoli etc and gives 15% protection. This is an interim measure only because it is affected by the wind so will be changed after this heat wave to something more robust.