Thyme-leaved Dragonhead / Dracocephalum thymiflorum

This rare plant in the Mint family (Lamiaceae) was growing in the only known place in Calgary - Bebo Grove in Fish Creek Park. This is apparently the most northern limit for this plant. There are two species of Dragonhead, one native and one introduced. My photo shows the non-native species. It always makes me wonder why a plant can be growing in one tiny location without spreading to other sites. Photographed on May 28th, when three of us did the May Species Count at Bebo Grove in the afternoon.