I'm starting to brain storm some ideas for next year's spring garden projects early and have soil amendments on my brain. Been fighting heavy clay soil in Alberta for years and am gonna stop amending it and just pull it all out and start from scratch.

There are things like bulk garden mix, which I might just use as a control in one bed, but want take a shot at building my own soil recipe. An ingredient that's come up sporadically, but doesn't seem to be widely used is crushed ceramic. A very porous material I'd think it's have great micro pore potential for water retention and mineral ions. My guess is that it's not used very widely because in large quantities it may be hard to find not contaminated with other construction materials.

I've found several people on classified advertisement websites in my area with PALETTES of un used roof tiles that I'm thinking of picking up and giving a go. Would have to crush them myself and will do some other research into the manufacturing process if there's some chemicals present in the ceramic I'm not aware of.

Has anyone here some thoughts on this idea?

I'd be using it in combination with bio-char, peat moss, crushed sea-shells, normal compost, and then the rest some regular "garden mix" from a bulk store locally.

  • 2
    Why don't you just plant plants that like living in clay, mulched with wood chips, if you can get them? Alternatively, why not use raised beds? Gardening should never be this hard.
    – Jurp
    Nov 11, 2023 at 0:26
  • Whether it's "very porous" or "not porous at all, like lumps/shards of glass" depends on how it's been fired. This does feel like taking an absurd approach to a "problem" more easily managed.
    – Ecnerwal
    Nov 11, 2023 at 1:12
  • 1
    Per the first comment, because I want to grow food instead of ornamental shrubs. Otherwise yes, I do gardening around this area and see things like hostas, ferns, iris's, and some others do well like that. @Ecnerwal, I thought that firing's effect on the resulting texture really only applied to the exterior surface, but when crushed isn't it mostly similar? And about the simplicity part, similar to my other response, yes in most cases just mix some compost in with an existing garden mix; but I'm trying it out partly just to experiment.
    – AustinFoss
    Nov 11, 2023 at 2:35

3 Answers 3


Ceramic has been fired to about 2000°F. It is unlikely to be very porous.

And if it has been glazed, then you don't know what chemicals it has. There are literally 1000s of glazes (my wife is a potter). The glazes may contain chemicals, metals and oxides. Although, unless you are using tens of kilos of it, the chemical levels may be low enough to be harmless.


  1. When the glaze is intact on top of the ceramic, it is not dangerous to health. However, as soon as you start crushing and pulverizing it, its a different story.
  2. Cheap ceramic mugs, that are mass imported have not been fired at a high enough temperature, which is why the glaze breaks down.
  3. Cheap tiles that are imported are again not fired at a high enough temperature and may be porous. I have experienced the porosity myself. My test is to take a sample tile home, weigh it, dunk it in a pail of water overnight and weigh it again.

Crushed or broken brick may be a better bet.


You might want to review the experience of a method studied by Cornell University for growing street trees in a mix that can withstand compaction and still allow roots to grow through the medium. Their specific concern is the need for compaction for heavy traffic which is not a concern in your situation, but you might learn some helpful details from the method.

  • Most interesting to me was "Structural soil less than 24” deep is inadequate for tree growth". Many trees appear to have roots that grow wide but not deep in soil. For their mix deep appears to be the way to go.
    – kevinskio
    Nov 14, 2023 at 15:22

As long as it's not made of heavy metals. baked ceramics used as soil amendments for millennia. Google "Terra Preta" However, The broken pottery has to be low fire to be better absorbent. Low fire ceramics may be crushed and added to the soil the pieces will act as little sponges and absorb the water and release it as the soil begins to dry or drain.

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