Eponymous botanical names should be pronounced like the person's (or place's, etc.) name would be pronounced.
So, Heuchera is pronounced "HOY-ker-uh" in recognition of Johann Heinrich von Huecher (German physician & botanist). I've heard "Heuchera" pronounced correctly on occasion but not often.
Likewise, Fuchsia should be pronounced "FOOKS-ee-uh" for the German botanist, Leonhart Fuchs. However, I've never heard anyone use the proper pronunciation for this one.
There are many more eponymous botanical names that are commonly mispronounced.
