Ack... I certainly did not mean to suggest clumping kitty litter ... There are brands of cat litter which are 'known' to be fired clay similar to turface, but much cheaper. I have myself used the basic cat litter from Walmart as a seed topping and have not seen any breakdown yet over the last 3 years. I understand that these materials are 'different' - that's obvious - but do they have substantially different properties in soil mixes ? Chad -----Original Message----- From: firstname.lastname@example.org [mailto:email@example.com] On Behalf Of Lee Poulsen Sent: Thursday, July 12, 2012 11:00 AM To: Pacific Bulb Society Subject: Re: [pbs] Growing medium On Jul 12, 2012, at 9:28 AM, Chad Schroter wrote: > > Most of the components are fairly inert; I have read that calcined clay (kitty litter, turface, drystall) has cation exchange properties, which apparently means it can store small amounts of nutrients (if present from added fertilizer), but other than that it seems to be personal preference ? > I don't think kitty litter, turface, and drystall are similar at all, at least the varieties of each that I've used. I would never use kitty litter in a mix because it's biggest property, that it clumps together into a hard ball when it gets wet, is exactly what I don't need to happen. Turface seems to be exactly as described: small bits of inert hard clay. But I have trouble finding it on a regular basis, and it isn't as cheap as other materials that are just as good (such as crushed scoria or lava rock). Drystall is just very small pumice; I use it in my seed starting mixes. But last time I went to get a bag from our local cactus/succulent nursery, they said it isn't available any more. Anyone know what happened? --Lee Poulsen Pasadena, California, USA - USDA Zone 10a Latitude 34°N, Altitude 1150 ft/350 m ________________________________ PLEASE NOTE: The information contained in this electronic mail message is intended only for the use of the designated recipient(s) named above. If the reader of this message is not the intended recipient, you are hereby notified that you have received this message in error and that any review, dissemination, distribution, or copying of this message is strictly prohibited. If you have received this communication in error, please notify the sender by telephone or e-mail (as shown above) immediately and destroy any and all copies of this message in your possession (whether hard copies or electronically stored copies).