Wicking beds come in a variety of sizes and styles. They have one thing in common: they are self-watering pots with the only drainage a place for water to overflow.
Here we have 2 types of manufactured ones, some big plastic bins, above-ground beds converted into wicking beds and pots of various designs all converted into wicking pots.
It's good to have them on a level hard surface. They work nearly as well when not so level though.
The mix is as varied as the people making the beds ... mine is layers of el cheepo potting mix for the reservoir. Followed by (in no particular order) Vermiculite, compost, more potting mix, soaked fine and coarse coir, composted animal manures. After a while the layers all blend in.
Up-sides as you know are water-saving - or perhaps better water-use by not watering more soil than is necessary.
Then being able to garden on a slope and having plants growing without root competition when there's trees nearby.
Down-sides: plants especially trees, need a tad more TLC than when they live in the ground. Even a 200L pot is a restriction for a large tree so add fertilisers more frequently than you would were the plant in the ground.
Microbes and worms must be added since the beds are remote from the soil. Once the microbes are active and the worms chomping, just some upkeep will see them happy and breeding. Using a Worm Tower (see Darren's articles on BLF) can be helpful for maintenance.
Colin Austin from Bundaberg popularised the wicking principle. He maintains a huge website with abundant information. The site is well worth several hours of time as he discusses so many topics around water and the wicking beds. Go to waterright.com.au.
On the BLF site, search for 'Wicking Beds' and there are several articles from different members plus photos. Worth a read.
I'm happy to correspond by email and answer questions if I can. Though it's often useful to post questions in the Wicking Bed Group so other members can participate and learn.
Is there an optimum depth for the reservoir material and again for the soil above it? I'm thinking of the ability of the plants (small things like lettuces, greens, etc) being able to reach the depth of the reservoir.
You don't mention liners Elaine. Do you still use these yourself? Personally not fond of metres of black plastic being involved in my food production.
Can I take this opportunity to remind everyone that searches on the site only work well if we add our Tags. Tags are vital to finding information again.
Not sure what to mention, Lissa ... it is a vast subject.
I use liners to make something water-tight. Without the liner there is no wicking bed if you modify existing pots with many drainage holes or make above-ground beds into wicking beds. I'm not wild about the plastic either. Unless you can find e.g. old baths and have a way of getting the overflow to work, then using plastic in one form or another is all we have.
Without having refreshed my memory of what is on Colin Austin's site, I'd go there first and see what he has to say. Yes I have found that some beds are too deep for what I planted in them - the narrow tall Hills beds are one such. Lettuces do have an extensive root system yet growing them in a shallow container (say 6-8 inches deep) works well. I have modified many basins and grown Lettuces in them; keeping the root run cool is a major challenge.
Thanks Elaine. Could be a long time before I am faced with the problem of creating my own wicking beds. I'll continue to research until then.
In your travels you're bound to find umpteen variations on the theme. A lot depends on what you want to grow and the aspect. It takes some experimenting and until you actually get down to it, you'll never know what works and what doesn't.
I have found that the commercial self-watering pots often have too big an overflow with a too-small reservoir. I have some beaut bins here I bought for $10 throwouts - they had a grid thing and a big slot for an overflow. Found the cane toads could slip in thru the slot and sit themselves in the water. Subsequently I booted the cane toads (they make great in-situ compost), chucked the grid into the recycling and re-jigged the overflow higher and smaller. Lined with plastic, filled entirely with mix and now they work just fine and the cane toads are deprived of another home. Little details like this escape our attention until faced with an issue you'd not think of by yourself.
Once Elaine found Colin Austin's site we both rooted about the net and found umpteen sites all with good if differing advice. Wicking Beds have taken off now and there will be more info available. Working your way through Colin's site though will answer most questions. It is a big site yet worth the effort in reading through as much as you can.
Got me thinking about the depth roots reach for the plants we commonly grow here for veg. Found this SITE which gives some idea - albeit in inches.
There will be a segment on Wicking Beds in the Gardening Australia programme on Saturday 11th March 2017. Looks like they are going to use scoria for the reservoir fill.