Capillary beds provide a constant source of water to potted plants. They use a capillary mat or a cheaper substitute to wick water from an unglazed earthenware pot to other plant pots sitting on top of the fabric, up through holes in the pot bottoms.
I have been making self watering planters for a number of years now. Strange that I have neglected to take a picture of the build.
I start with a deep Rubbermaid tub, the deeper the better.
first I cut a piece of 3" black plastic pipe the height of the tub and set it in a corner of the tub,
then I half fill the tub with lava rock (because it wicks water very well)
On top of the lava rock I put a single layer of plastic bug screen,
and top it off with soil mix.
After the initial watering (which sets the dirt into the screen), all subsequent watering is done by filling in the black tube.
you can look in the tube to see how full the reservoir is and just top it up when needed. for house plants, this is once every 4 or 5 months. As long as there is any water in there, it will wick.
As a measure of it's ability to maintain moisture, last year I had a tree frog come in my open window and it spent the summer days in the plants and the evenings in the tube.
I know that a big Rubbermaid tub in the living room is ugly, so I build wooden boxes to conceal the tub. In the end it looks like a nice wooden planter, but it has the waterproof nature of the Rubbermaid, and a constant supply of water despite my inability to water plants weekly. I see no reason why this wouldn't work for food plants of all kinds as long as you maintain an appropriate soil depth (to keep the roots out of the bug screen.) The roots would be happy enough to grow onto the lava rock below as there is air down there just above the water level, but pulling roots back out of the bug screen would involve rebuilding the whole mess. A tub of straight lava rock also works, but the water evaporates relatively quickly without the soil cap.
We made several large wicking pots from old totes. They work great. if you google Gardening with Leon he has you-tube stuff showing how to make them from recycled materials. we are sold here, will make many more
I grew an award winning african violet by wicking. This was late 1990's. Pots were small 2" pots and one strand of yarn was enough to keep it moist. I had a flat tray filled with water then a rigid screen over that and the pot sat on the screen. I used a pencil to push the yarn in from the bottom. It worked well.
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