I recently purchased filter fabric to install in my new plant containers. I expected the fabric to be pervious to air and water and prevent soil from washing down into the drainage layer (crushed clay and rock) at the base of my pots. I potted three shrubs with the fabric in place and gave them all a good soak... but afterward noticed with some alarm that no water had drained out the bottom of the pots... not a drop! I tore off a patch of the filter fabric (see photo attached) and poured water on it to test its permeability. The water beaded and slithered around the surface of the material but it did not quickly soak in or pass through. Alarmed, I phoned the nursery from which I'd purchased the material and voiced my concern. They replied: "Don't worry. It takes a while to soak in first and then slowly water will drain through." I'm not quite convinced. Does anyone else have experience with this stuff? Shouldn't it allow relatively free passage of water?
Unless these are big mall-sized planters you don't want a layer of rock or crocks in the bottom anyway. These will impede drainage whether the cloth also does it as well or not. Put potting medium all the way to the bottom of the pots and forget about the rest, the same treatment millions of plants in commercial growing operations get.
Regarding your specific question, yes this stuff does repel water somewhat when first installed. We use something similar under our nursery containers to manage weeds, and it does indeed have water pooling/beading on it at first. I have seen advice to spray it with a surfactant when first installed, to break down this waxiness or surface tension. Remay/etc. also has this property at first, kind of maddening as you're attracted to the idea of being able to sprinkle plants with that stuff covering them, not having to pull it off and back again all the time! What Ron has said is also totally correct, however. You don't want coarse material in the bottom of any plant container. You can look up info on "perched water table". Water will collect in the bottom of any uniformly filled container and drip out when the laws of physics dictate...strange I know if you've "learned" from those generations of gardeners who have faithfully "crocked" their pots when planting, but it's one of those things that belong on Mythbusters.
consider capillary action. coarse to fine will always drain down, fine to coarse will likely not. the finer particles 'hold' the moisture droplets tight and the coarse particles dont have the attractive ability to pull it out. until it reaches field capacity where gravity wins. I do as Ron says, just fill the pot with growing medium and let'er rip.
