Duncan wrote:
Hi

For no other reason than it interests me I'm trying to get my head
around the way plants are named.


Varieties are, strictly speaking) naturally occuring and are usually
named with the abbreviation var. e.g. Callirhoe involucrata var.
lineariloba. But see below...

A cultivar is a variety developed or propagated in cultivation.
Sometimes plantsmen will take a naturally occuring variety and develop
it further on purpose, or else they will take a nice representative of
the species, slap a name on it, and charge more. Cultivar names are
written with the letters cv. and the cultivar name without quotes OR
they are written without the letters cv. and the cultivar name in single
quotes. e.g. Caryopteris clandonensis cv. Longwood Blue or Caryopteris
clandonensis 'Longwood Blue.' It often happens that a cultivar is a
hybrid of several species, in which case you may see a plant name with a
genus designation, no specific epithet, and a cultivar name. e.g.
Paphiopedilum 'Madame du Bovary-Plessis.' (I made that example up, but
you get the idea.)

A forma, strictly speaking, is a naturally occuring form that is only a
minor variation on the "normal" form. For example, there is a gorgeous
blue-flowered form of scarlet pimpernel, which usually has salmony-red
flowers. It is called Anagallis arvensis f. foemina.

To cloud the issue, though, it must be noted that plantsmen commonly
take these forms, slap cultivar names on them, and propagate them to
maintain the desired variation. There is also a looseness to the
English language that leads everyone to use the word "variety"
informally to apply to true varieties, to cultivars, and to forms, as in
"I saw that variety once when I was in Vancouver."

Your example of Ajuga reptans 'Burgundy Glow' is an example of a
cultivar. As to the origin of the cultivar--natural, bred up, or purely
illusory and for profit, one can't know without some research...

Clear as mud, yes?
Monique Reed
Biology Department
Texas A&M