On 2 Jul 2013, at 15:33, Ina Crossley wrote: > I am using pumice in my mixes, but only recently. I bought the 7mm one > which seems to have a lot of dust and small stuff in it. Does it still > do it's job of drainage with all the small stuff filling any gaps. If you intend to pot up a plant in nothing but pumice, be sure to wash it. I have found that otherwise, the fines are washed down to the drainhole, pile up against the piece of fly screening I customarily put over the hole, and block drainage. Pumice by itself is a very good potting medium for certain plants. I use it for Weldenia candida (which happens to grow natively near the tops of Central American volcanoes, according to the literature), and a few honest-to-God high alpines. Pumice is actually quite nutritious in a limited sense, containing a lot of potassium. You are justified in your unhappiness with this supposedly-washed pumice you've been sold. Even when it's going into a potting mix, I wash it first over a It's shocking how much fine material comes out. -- Rodger Whitlock Victoria, British Columbia, Canada Z. 7-8, cool Mediterranean climate