Picture of Physostegia virginiana, commonly called, "false dragonhead" flowers (sometimes spelled "dragon head")....
False dragonhead picture.
False dragonhead flowers are late-blooming perennials
, as their pinkish-lavender blooms burst forth in August. Their late-blooming quality helps extend the season of floral color in the yard. This plant is a vigorous spreader and will last for years without division, but if you do wish to divide
, spring is a good time (although time probably does not matter, as this perennial is virtually indestructible).