Sub-Irrigation
low effort bucket-gardening
(all credit belongs here)
The idea is to create a reservoir of water in the bottom half of a bucket which will be wicked up by potting mix. This is achieved using a smaller perforated container inside the bucket, and a PVC pipe adds water to the bottom level.
The finished result is captured in this detailed diagram:
Supplies
For each planter you’ll need:
- A five gallon (20L) bucket
- A smaller, two gallon (8L), container e.g. bucket, milk jug, bottle (holes will be drilled in if not already there)
- 40 cm or so of 2-5 cm PVC pipe
- A drill or some other way to make holes roughly 8 mm
Additionally, you’ll need:
- Potting mix (quite mossy for wicking)
- Perlite (optional, but good for speed and keeping dirt out)
- Fertiliser - the numbers mean:
nitro%-phosph%-potass%and do not have to be precise. - 5-5-5 non-soluble
- 20-20-20 (high N) soluable
- 10-55-10 (high PO4) soluable - only for fruit/veg not leafy greens
Assembly
- Cut an end of the PVC pipe at a 45 degree angle so it won’t sit flush
- Place the perforated inner container upside down at the bottom of the larger bucket, and slot the PVC pipe in next to it (angle end down)
- Drill an overflow hole in the side of the large bucket two inches below where the top of the inner bucket will be
- Fill the bucket with perlite until the inner container is just covered
- Add potting mix to cover the inner reservoir by another two inches, and moisten it with water
- Layer half a cup of the 5-5-5 non water-soluable fertilizer
- Fill the rest of the bucket with potting mix, and water it thoroughly (the mix needs to be moist to start wicking)
- Plant plants
- Pour a mix of 1tsp of high N fertiliser per 4L of water into the PVC pipe until it flows out the drain hole
Care
- If the potting mix dries out it won’t wick new water up
- You’ll probably only need to water once a week (but more won’t hurt)
- Mix 1tsp of water soluable fertilizer per 4L of added water
- When fruiting/flowering switch from high N to high PO4 fertiliser