Building a Covered Wicking Bed


| 11/17/2020 10:04:00 AM


Clinker cinders, also called scoria or lava rock, is great for the base layer of a wicking bed 

Clinker cinders, also called scoria or lava rock, is great for the base layer of a wicking bed.

I have been interested in aquaponics and hydroponics for a long time, and they are the reasons I built the nice personal greenhouse that I built at my home. Our growing season is fairly short here on the Southern Colorado River Plateau of Arizona, and winters can be bitter, bitter cold, so the greenhouse made sense for that reason as well. I spent years researching various methods and setups for both growing styles and one doesn't spend much time researching hydroponics or aquaponics without learning about a wicking bed sooner or later. 

Popularized by Murray Hallam of Australia, the wicking bed works much like an oversized self-watering pot. The water, whether from the fish tanks as in aquaponics, or nutrient water, like in a hydroponics setup, sits under the growing medium and wicks itself upwards, keeping the growing medium moist, but not soggy, and growing the plants in the top. 

The beds are very often fashioned out of large fish tanks, vinyl-lined wooden grow beds, or even old stock tanks, just something that will not leak and is at least 24 inches deep or so. A fill-pipe, usually like a 1.5-inch or 2-inch PVC pipe, is run down from the top of the bed to the bottom. Some designs have notches cut in the bottom end of the PVC to allow water to flow down, some have holes. Some designs, like the one I found, uses an elbow and a bottom pipe that runs the width or length of the bed, just for filling ease and to help the pipe stand upright. 



The beds are filled to a level (at least 8”, but could be more) with some sort of very coarse scoria (also called lava rock or clinker cinders if you get them from a landscaping company, see photo above), then covered with a sheet of landscaping fabric or fine shade cloth, so moisture can wick through, but it will hold the planting media from going down into the water. An overflow pipe should exit the wicking bed just about the level of this landscape fabric, so that water doesn’t accumulate at the planting media level and leave everything soggy. The planting media, in my case a mixture of peat moss, good quality homemade compost, and some store-bought organic potting soil, is laid on top of the landscape fabric, at least 12 to 16 inches deep. The water then wicks up through the landscape fabric into the planting medium, supposedly keeping it moist. (See terrible drawing that I made, below)





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