Jamie, there are plenty of aquatic plants, but we seldom grow them as container plants in soil. I would not consider a willow tree to be aquatic. All the willows on our property grow in areas where the ground dries out occasionally during the growing seasons. They are never in a constant state of being waterlogged. I think maybe you're thinking of a mangrove environment, as opposed to a rain forest. In mangrove swamps, plants and trees have adapted to being in water. In a rain forest, the trees have adapted to seasons of high humidity and lots of rains. Orchids, for example, enjoy the humidity and rains, but couldn't be grown in a constant state of wetness. I'm not really knowledgeable enough to explain the chemical breakdowns and the science of it all, but I can tell you that in nature, there's a certain balance kept by all the living and non-living organisms and the constant decomposition going on. It's a cycle that works very well in a garden environment... but it doesn't work in a pot. Within the confines of a pot, it's next to impossible to keep everything in a state of balance because the same living organisms are not present cycling the decomp... and an organic environment in a pot can quickly become unbalanced and toxic. That's why it works best to keep a more inorganic medium in containers. Perhaps Al or someone can explain mycorrhizal fungi, which have a symbiotic relationship with plants, and how they fit into container growing. There's a huge difference between water in vapor form, or being slightly moist... and being in a constant state of wetness. Most container grown plants dislike being consistently wet. The roots can't survive being waterlogged all the time. They need oxygen and a chance to "dry out" for periods of time, and a fine, compacted soil that holds too much moisture for long periods of time does not allow for the necessary exchange of oxygen and gases. I'm probably doing a poor job of explaining it... we can't really talk about growing in the ground and growing in a confined container in the same breath... the two environments are at opposite ends of the growing spectrum. Instead of comparing the two environments, I think of them as two completely separate subjects. Each has a different set of needs. In a garden, nature controls most things... in a pot, we are in control... we are playing the part of Mother Nature.

Perhaps others with more turface screening under their belt will say something, but my general understanding and experience is that turface is mostly correct sized particles + dust. My 50lb bag was like this. I can't recall what yield I got after screening, did most of it a few years ago. Maybe your and/or my bag are outliers. Here's an old thread with some information from Al and others that specifically mentions insect streen and yield variability, there's plenty more if you search this forum some: http://forums2.gardenweb.com/discussions/1420911/screening-turface Daniel

If you are looking for a defining line or percentage, I don't think you'll find it. As you increase retention and decrease particle size it is a relatively continuous compromise. How much that affects you depends greatly on growing environment - ideal or near-ideal conditions are much more forgiving, such as if you live somewhere temperate, with lots of light, and good airflow. I screen my Turface with a kitchen sieve and there is not much 'waste'. Which is not really 'waste' because I use the fines for seedlings. At this size, it's very little for a large bag. Not really an answer I suppose, but perhaps something to think about.

Thanks Lauren and Greenman. I'm trying to avoid screening and sifting due to space and dust issues, so you're right that I should just buy the right size fines - but that's the problem - citylife has its limitations. I can't find them except for tiny bags online that cost a fortune and I have a whole bunch of large plants. i just found this on amazon - price seems too good to be true for the perfect size. Pine bark that apparently has been heated to be aged?? So can you tell me if this so-called Deep Jungle Bark (pine) would work for gritty? Thanks much for your time and help marie Description Deep Jungle Bark 1/8 inch to 1/4 inch - 24 quarts.Stable and pH adjusted medium does not accumulate unwanted salts; temperatures exceed 150ºF during the aging process, so pathogens cannot grow and any present are killed; natural colonies of beneficial micro-organisms flourish; aging removes waxes from surface of bark chip, allowing Deep Jungle Bark to hold water & nutrients on outer surface; unlike fresh bark, Deep Jungle Bark's aged surface provides instant & consistent rewetting; excellent delivery of water & nutrients from day About this item Features Deep Jungle Bark 1/8 inch to 1/4 inch - 24 quarts Use for pet habitat substrate AND/OR for growing orchids. Deep Jungle Bark is naturally decorative, washable, and reusable. Deep Jungle Bark gives consistent hydration, an ideal wet/dry cycle and provides excellent longevity. What makes Deep Jungle Bark unique is the proprietary aging process which results in superior performance when compared to raw pine bark. The aging process destroys pathogenic micro-organisms while at the same time promoting the formation of beneficial organisms such as Penicillium and Trichoderma. Deep Jungle Bark is a sustainable growing medium produced from the finest quality, 100% pure New Zealand Pinus radiata bark. Pinus radiata is sourced from renewable, man-made forests ensuring availability into the future.