I should admit that while walking in Lefferts Garden, I saw a neglected rose mallow with bluish blooms. A normal rose mallow (hardy hibiscus) is pink or white.
Without thinking I tore off a small, flower less branch. To my surprise, it started rooting itself only says later.
With luck, the blue color won't be due to it's old growing environment. I'll know next year (or the year after?). It goes without saying that I probably shouldn't keep up this bad behavior.