I have been growing this plant in my Zone 5b-6a northern CT garden for three years in a partially sunny garden. The site is well mulched, and has relatively heavy soil.
Despite my reservations about growing a plant from a species known to be invasive, this plant has been well behaved and provides welcome color and interest in the fall.
The color is a very bright magenta--it is certainly eye-catching! I have it backed by a big-leaf hydrangea and farther back, a red upright cut-leaf Japanese maple. The leaf and stem structure of Persicaria amp. 'Firetail' is rather "viney," consisting of tall, thin stems, and pointed leaves, so the combination of leaf contrasts and colors work well.
It has been spreading slowly, and seems to be only slightly browsed by deer. Of course, it only takes one deer with gourmand tastes to ruin the planting!
Click on a thumbnail to see a full sized image