>In wet winter climates, "fast drainage" is very necessary to facilitate the quick drying which other climates experience. In Britain we can experience Spring, Summer, Autumn, and Winter in a 24 hour period. And I bet that this requirement has been misappropriated for cultivation techniques in semi-arid and arid environments. (No, I don't bet; I know it has.) Here's the Deno quote, from Seed Germination, Theory and Practice. "It is appropriate hereto clarify one of the most pernicious misconceptions in the horticultural literature, namely the subject of drainage. Growing roots are actively consuming oxygen. It is easy for them to be asphyxiated if the oxygen pressure is reduced below the 0.2 atmospheres that is present in the air. The susceptibility varies in different species. This subject is misunderstood to an incredible degree in the horticulture literature. The word drainage is like a drumbeat punctuating every paragraph. In fact a plant cannot possible care whether water drains fast or slow over the roots. What is critical is the supply or more precisely the pressure of oxygen. The word drainage should be crossed out throughout the horticultural literature and replaced by the word aeration. The misunderstanding arose because media that drain well usually are porous with 10-30% free air space so that they remain aerobic. What has happened in the horticultural literature is that an aeration requirement became misinterpreted as a drainage requirement. It can be added that if drainage were essential, plants could never be grown by hydroponics." Bob