Well I have looked but I have yet to find any in the wild. Supposedly its native to this area but hell if I can find em and I fancy myself pretty good in the woods. Bobrown is definitely one of the top two or three soil guys on this site, definitely recommend trying most anything he suggests.Have you looked at adding horsetail fern? Very high in silica plus also is a PM preventative. I add it in with my soil amendments and then ALL through Veg I use a horsetail fern tea as a foliar. You can spray this right before lights out with no worries of PM. Learned this trick from Bobrown14 and my girls seem to love it!