Heucheras are named after German botanist and his name as we all know is Johan Heucher. In german without any exceptions diphthong "eu" is always pronounced "oy", like in Europa"-"oyropa" or "eule"- oyle". Why,oh, why somebody insists of making us sound stupid and propagates pronunciation "Hyookera"! In what language "ch" is pronounced "k"? Swahili?
If we should agree that the guy's name is "Hoycher" by the right pronunciation than it is "hoychera" as the only way to call it,.