Stinging nettle
A sting that vanishes in boiling water. Free spinach, basically.
Urtica dioica — the sting you can cook
Nettles sting because they're full of tiny glass needles. Thirty seconds in boiling water destroys them, and what's left is one of the most nutritious greens you can eat for nothing.
How to pick
season spring, before they flower look for the young top four leaves leave any plant that has gone to seed gear gloves, or a plastic bag over your hand
What to do with it
Soup, tea, or wilted with butter like spinach. The sting is the only thing to fear, and heat kills it instantly.