Chocolate mint

Mentha x piperita. A perennial herb (hardy to zone 4). A remarkably prolific and hardy plant. To keep from spreading, plant in a sunken container (with drainage holes!). Or plant in a corner of the yard where you don't mind it taking over. Wonderful added to smoothies, added fresh to tea or lemonade, or dried for use in herbal teas. Attracts pollinators and is a great ground cover where allowed to roam free.