see also the DIY Colloidal Silver link in my sig, many years of Q&A and yep i wouldn't wanna smoke it... colloidal/elemental silver isn't the problem, it's all the dodgier things it can become via a reaction with other chemicals in the bud when you're burning it (i don't know which but just guessing possibly things like silver nitrate, silver chloride etc...). For this reason I would personally never "spray just 1 branch, and leave the left of the plant smokeable". And for that reason, I always just spray the entire plant with CS, seeing as I consider the whole plant a non-consumable write-off. ps. I'm not a chemist, I don't know how much silver is transported throughout the plant once foliar-sprayed onto one branch, and I don't know which silver-based compounds are created during smoking, but these are my concerns, and unless somebody can provide evidence that it's safe it just seems like a stupid thing to take a risk on ... use CS to create feminised pollen, nothing else.