If the results were in alphabetical order by species (when searching a genus,) that would help.
I don't see how a button or link to "remove cultivars from search results," would confuse people, or any other options to sort search results. If they didn't know what it was for, they would ask, ignore it, or experiment with it & self-teach.
If folks were going to be intimidated by something, I think it might be how their personal plant list is arranged only by botanical name, even though the common names appear first. It's so hard to scroll quickly through the list since one can't maintain focus on the botanical name used to order the list.
Hope I don't sound complain-y. Just trying to help make my fav plant forum site even better! This is where I keep my plant list & is the most useful site I know for plant lovers. Thanks to everyone who helps out!