[chawco]

Even a replacement is unnecessary — silphium was a commercially important plant traded in antiquity. It had well known uses in antiquity, was sought after (considered worth its weight in silver), was mentioned in literature of all sorts and appeared on coins. It’s also potentially where we get the heart symbol and its connotations in modern times (it is theorized to have been a contraceptive of some sort).

And it went extinct, and a we’re not quite sure why. Plants can be very useful and not survive attempts at cultivation before going extinct in the wild. It doesn’t need to get more complicated than that.