I've had it for five years, and each year it gives more blossoms in early May. Last year it did something odd. A few weeks after the large red flowers subsided, smaller, simpler, white-and-pink flowers opened, but on short, green stems as opposed to the typical woody tree peony stems.
Bonus! I thought.
Now this year, after a particularly spectacular show of red three weeks ago, it has happened again--even more white-and-pink, simpler blossoms. But I noticed something: not only where the flowers of more simple morphology, so were the accompanying leaves--simple, instead of multi-lobed. And again, they were born on green, non-woody stems. Hmmm, I thought. They look like suckers.
I googled tree peony suckers.
Aha! Something sinister is afoot. It turns out that tree peonies are propagated as grafts on herbaceous peony root stocks. Often, as in my beloved case, the herbaceous roots will reassert themselves, and act as if they were the raison d'être for the purchase at the nursery. They can overtake the tree peony, should its developing roots not prevail.
I found a Q&A site that described the sort of surgery one must perform to remedy this issue--involving the removal of the herbaceous roots from below the graft point. But if you do it incorrectly, you can kill the tree peony.
Oh that I didn't love my tree peony so much.