I have seen several instances where a plant is called "Taxodium x media" or Mahonia x media" in nursery catalogs. Does this refer to the plant being a hybrid of the species, or something else? This may be an example of creative taxonomy, or is it a legitimate usage, and if so, what does it mean? Thanks
The name is the choice of the person who describes the plant in the first place, it can mean as much or as little as that person wants it to mean. As "media" means 'inbetween', it is often used to denote hybrids, but it doesn't necessarily always do so. When there is an 'x' (or a times sign ×) in the middle of a name, that definitely means it is a hybrid. It can of course be followed by any name that the naming person choses, it doesn't have to be "media" (and usually isn't!). e.g. Larix × marschlinsii (Dunkeld Larch), which is named after someone called Marschlin, on whose property the hybrid was first found. When there is an x or × at the start of a name (e.g. × Sorbaronia alpina), that means it is a hybrid between plants in two different genera (in that case, Sorbus aria crossed with Aronia arbutifolia). Oh, also, don't confuse an 'x' which is an integral part of a species name with a hybrid sign! - e.g. Rosa xanthina, where "xanth-" (from Greek xanthos, yellow) just means it has yellow flowers; it isn't a hybrid at all.
That x before a species-level name is commonly (incorrectly) used by nurserymen to mean anything that is any kind of hybrid. Instead it is to be used only for hybrid combinations that have received a specifically published cross name; in this case, all hybrid crosses between Mahonia lomariifolia and M. japonica are called Mahonia x media. So your plant is likely a random seedling with those two species parents. If it had an additional cultivar name, like Mahonia x media 'Charity', then it would be a specific vegetatively propogated selection from within that group. All plants with a cultivar name (like 'Charity') will be identical and may have been selected as superior; all plants with only a hybrid name (like x media) will likely have the usual variations that different seedlings do. :) - Tom edit: I don't think there is a Taxodium x media, could it have been Taxus x media (T. cuspidata x T. baccata)?