"Now if I could kill my garden weeds like that, I'd be all over it!" - Amey
Going somewhat off-topic, Lol - There is a minor flaw... The idea, in itself, might be workable.. Weeds stick up above ground, the roots go down and are, well, well grounded... So - Zap a high enough potential to the protruding weed, and you will induce a current in its entire "body"..
Sufficient current will I imagine cause enough heating to destroy the weeds celular structure..
But getting yourself to high enough potential would be difficult - and zapping the weed with your finger would probably be as fatal to you as to the weed...
But perhaps a portable variation on a tesla setup, with a "applicator" you can zap weeds with...
One would get the added advantage that you could probably find loads of kids willing to zap your garden with lightening bolts, free of charge (in fact, you might even get them paying you! ;-) .. But just be sure they dont get into a fight.... And be sure they dont accidentally zap some crystaline alien entity which has been quietly minding its own business in your garden for the last few millenia.. ;-)
Fred.
ps.. I like weeds (or most, anyway - the vine types - bind-weed and that class - which strangle other plants are the only ones I really bother with).. I much prefer a wild natural garden.. A Tazer to zap weeds would not be high on my list of things to buy or develop.. But its probably an idea which I could get funding for a lot easier than I can get funding for theremins - So, lets see... Weedkiller Theremins Foundation ...... Or WTF Inc..