Last year I latched onto the idea of making free fertilizer by
collecting nettles from the local park in a big plastic pretzel jar,
filling it with rain water, sticking the lid on, & letting the mix rot
for a week or two until it smelled like sh^W fertilizer; then I poured
the stinky green liquid into my containers.

It turns out I should have strained it through cloth (or some similar
procedure): I never had nettles in the garden until now (& they're in
some of the containers).