Now that's a mouth full of Latin, isn't it? I believe that you'll find that if you say it fast three times, Persicaria polymorpha is easier, however, than repeating "giant fleeceflower" quickly three times. This beast of a plant lives in my front landscaping, near the walkway, and it always causes a scene when a visiting gardener sees it in flower.
I discovered it myself several years ago while on a gardening tour in the neighboring county where it was shining brightly and stealing the show at a friend's garden. I immediately left the tour and proceeded to my then-favorite garden center to ask if she had any. Thankfully, she had one small plant left over from a custom order for a landscape job and I took it home and planted into a nice spot. One thing to admire about Persicaria; a small plant will flower and one year later it will be spectacular!
I called my giant fleeceflower a beast, but, other than its size, it is an impeccably well-restrained garden citizen. Actually a strain of knotweed, Persicaria polymorpha might flop on some more diminutive neighbors after a heavy rain, but it will soon stand itself back up (mostly) as it dries. It helps if you don't ever fertilize giant fleeceflower, starving its growth to stay within the constraints of its genes. It doesn't spread by runners or self-seed, as far as I can determine. I've recently divided my now 5 foot diameter clump to start others in my garden and it is as simple as dividing a daylily. Well, perhaps similar to dividing a slightly tough-rooted daylily. I'd certainly recommend putting it among shrubs or perennials. Standing alone in a lawn, Persicaria will just look like a big weed you should have removed.
Persicaria polymorpha was formerly known as Polygonum polymorphum. Because of its good behavior, some speculate that it is a hybrid, rather than a species. It grows about 5 foot tall, takes all the drought and sun you can throw at it, and is hardy in the worst of my Zone 5 winters. A perennial, all the care that giant fleeceflower needs is to cut it to the ground each spring. No pests seem to bother it, it blooms all summer long from early June through mid-September, and those creamy white panicles don't brown and enter an ugly phase. Even in my hot Kansas sun, I might call them a little "toasted", but they primarily stay creamy for a long time and then turn reddish-brown in fall. I leave them on all winter to provide some structure in the snows.