Nasturtium vs. Nasturtian
The English seem to have a problem when referring to a pretty
trailing garden plant with bright yellow or red flowers
1 that grows in their gardens... When I was little we were
wont to say "Nasturtium", until our grandmother corrected us: "it's
Nasturtian!" Indeed the OED records the usage of
"Nasturtium" as "improp.", improper that is.
So, you might ask, if "Nasturtium" is wrong, what is it? The
OED says it is "kinds of pungent-tasting cruciferous plants
including watercress", but this little anecdotal conversation between
J.R.R. Tolkien and his college gardener sets the record straight:
I consulted the college gardener to this effect: 'What do you call these things, gardener?"
"I calls them tropaeolum, sir."
"But, when you're just talking to dons?"
"I says nasturtians, sir."
"No, sir; that's watercress."
And that seems to be the fact of botanical nomenclature...2
Tolkien, a professor of English himself, dug his toes in so about
his publishers silently mis-correcting his words (e.g.
try to say
for try and say
and so on"3
that not proving that he was talking about "Indian Cress" (yes, it's the
one with pretty flowers!) and not ordinary watercress was out of the question.
Indeed our own Webster is quite wrong in his
second definition of "nasturtium":
"Any plant of the genus Tropaeolum, geraniaceous herbs,
having mostly climbing stems, peltate leaves, and spurred
flowers, and including the common Indian cress (Tropaeolum
majus), the canary-bird flower (T. peregrinum), and
about thirty more species, all natives of South America. The
whole plant has a warm pungent flavor, and the fleshy fruits are
used as a substitute for capers, while the leaves and flowers
are sometimes used in salads."
1 The Concise Oxford Dictionary, 1964 ed., p. 801
2 The Letters of JRR Tolkien, 1995 ed.: no. 148, p. 183