Russian sage

I always think of Russian sage as being a quintessentially New Mexican flower, especially against adobe walls.  Only of course it's not: it's an imported species: Perovskia atriplicifolia.  Actually, it's not even known as that, officially, any more, but Salvia yangii: it's been acknowledged that it really is a type of sage (and, who knew?  One can eat its flowers!).  I suspect that it suffers badly from an identity crisis, because it's not Russian, either: the English botanist George Bentham (Jeremy's brother) gave it its Latin name in 1848, when he inspected a plant brought by William Griffith, another British naturalist and botanist, from Afghanistan (it's now in the Kew Gardens herbarium).

We have three of these plants, which always do the same thing: one - this one - grows extravagantly and beautifully; one remains spindly and a bit sulky; and one doesn't get beyond the stage of being a low - a very low - bush.  Since they all grow in equally bad soil, and all get watered, I don't quite get it.