I tried the groundwater still 3 times. One was locally in our Oak Riparian Woodland, the Joshua Tree Desert near Edwards AFB and finally in the Coastal Redwoods. Each time was an abysmal failure. The "sweat equity" investment surpassed the meager returns. A friend quipped I at least A. created a subsurface shelter or B. my own grave <img src="images/graemlins/blush.gif" alt="" />. Transpiration units utilising living vegetation are more productive, with this caveat. Some plants will pass on a degree of toxicity or oils and may be externally contaminated. The PT 109 survivors discovered this by licking guano covered leaves in the dark. I watched an archaeological site volunteer ( 1/32 Winnebago tribe) try this stunt with Poison Sumac. My copy of Munz went unheeded <img src="images/graemlins/confused.gif" alt="" /> " I'm a native American dude <img src="images/graemlins/smirk.gif" alt="" />"