I didn't read every reply, but skimming through this feed i am SO surprised to not have seen anybody answer with NETTLE!!!
Nettle grows everywhere and provides fresh greens for us in early spring. Traditionally people know nettles as a stinging plant but once you cook them or pour hot water over them the stinging action goes away!
They are an herbal nervine tonic meaning they are wonderful support for our nervous system. Overall they are a very nutritious green that grows literally everywhere. The seeds are also extremely useful and medicinal as well.
