Available oxygen is necessary for successful seed germination, which is one reason why most seeds in saturated, dense media don't germinate as well as those in a loose medium. I was just reading an essay that referred to the observation that precipitation from storms contains a higher proportion of 18O (sorry, the 18 should be superscript) than the more common 16O isotope. This reminded me of hearing that some growers assert that exposing seed pots to rain and, especially, snowmelt, would encourage germination. Does the isotope of oxygen matter here? Or is the oxygen in water not available to the seeds? When I lived in the foothills where snow was more frequent, I would cover my seed flats with snow and let it melt, just in case what I'd heard was true. Have you heard these theories, and do you know if there's any value in them? Should I again start covering my seed flats with snow, in the event that any falls here near Portland this winter? Jane McGary, Portland, Oregon, USA _______________________________________________ pbs mailing list pbs@lists.pacificbulbsociety.net http://lists.pacificbulbsociety.net/cgi-bin/…