This is a new one for me and maybe for many people from regions with a temperate climate, although perfectly cold-hardy. Grown mostly as a perennial (ie., cut back in the spring) it forms a well-branched clump that erupts in flower when you least expect in September, with long spikes of pink flowers, which are very attractive for the pollinators; the species is listed as an important honey-bee food plant!
The whole plant exudes a mint fragrance, hence the name. It doesn’t form rhizomes, so there is nothing to be afraid of except the fact that you would like to hang on more in the garden later in the fall. Some years it won’t get to set seeds in our zone 5, so take advantage of these now. Read about it and see more pictures of the mother-plant – here.
Germination: said to germinate easy, sow in the spring.