65L tubs from Bunnings. They are black "recycling" tubs. I searched for the highest sides I could find in order to maximise the soil depth. 400mm would be ideal (70mm reservoir and 300mm soil with a bit of room at the top), but they are a bit short of that.
I used 90mm PVC pipe in the corner as a filling and inspection point. It is a bit large really but I had some short lengths on hand. A short section of ag pipe has been added to spread the water, but this is probably overkill for such a small tub.
Outlet holes are drilled to allow excess water to escape. These are 70mm (at bottom) from the base. The holes are 20mm in diameter. The stones (forming the reservoir) fill to this depth.
The tubs must be completely level, hence the wooden stand. I have three tubs which neatly fits under a window with an awning. The messy packing of the base will be hidden by a planter box.
Stones are placed in the tubs to form the reservoir. This is 25mm scoria, quite cheap.
Non-woven weed mat is placed over the stones. It will act as a wick so the non-woven variety is important. It feels more like cloth compared to the woven stuff which is like a very thin nylon tarp. The weed mat is turned up the sides to cover the overflow holes.
The tubs are filled with soil. I had delivered a mix of 2:1:1 of mixed soil, mushroom compost and organic compost. The mixed soil is already a mix of loam, mushroom, organic and peat but I read that a heavy organic soil was needed to draw the water up. Time will tell.
I made three tubs and plan to construct a planter box around them. They sit against a North facing wall. This will be great in winter but come summer I can see the plants getting cooked. I plan to attach shade cloth to the awning above. The awning also dictates that no tall or climbing (trellised) plants can be grown but given the shallow depth of the tubs this was always going to be the case.
I’ve put in seeds for Bok Choi, Asian Vitamin Green, Thai Basil and Coriander. The third tub will probably get Spring Onion.
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