False heather.

Yes, the cuphea is sometimes called heather. More often it's false heather, though.

But usually, it's called wax weed.

And Cuphea and Calluna aren't even in the same family: one is in the Lythraceae (like loosestrife and henna) while the other is in the Ericaceae (like uva ursi, rhododendron, and bilberry, to mention a few).

The only thing they have in common is their looks: they're both compact shrubs with pink flowers.

And there's a lot of small shrubs which grow on bare, rocky places. Flower color is completely incidental.

Yet here's a website which mentions both in the same sentence ... http://www.innvista.com/health/herbs/heather/

They're not interchangeable.

Heather (Calluna vulgaris) is a nice herb to make you sleep (if you pick only the flowers), or to strengthen your kidneys (if you pick flowers + leaf).

False heather (Cuphea spp.) is a simple astringent.

I'd have put up two different entries.