Some of the sub species of S. rubra are quite similar to some forms of S.
alata. In particular S. rubra ssp Jonesii has a remarkable resemblance to
some of the Mississippi clones of S. alata.
There are a number of reliable differences though.
Generally S. rubra is a much smaller plant than S. alata, particularly in
the spring when the pitchers of many S. rubra sub species are small, thin
and often quite ensiform. There is a very large variant of S. rubra ssp
Wherryi which can get to a similar size to S. alata but you are unlikely to
encounter this one by chance. Also the pitcher mouth tends to slope
downwards when viewed from the side in S. rubra, whereas in S. alata this
is pretty well level.
Fuzziness is not a reliable indicator since some sub species of S. rubra
are typically fuzzy, in particular S. rubra ssp Wherryi which overlaps the
range of S. alata in southern Alabama.
Flower colour ought to be a good indicator, since the flower of S. alata
varies from a pale cream colour to yellow, whereas that of S. rubra is red.
Unfortunately this is not altogether fool proof since there is a yellow
flowered variant of S. rubra ssp Wherryi. A better guide is flower size
which is always much larger than that of S. rubra and the scent - flowers
of S. rubra species are distinctly rose scented.
If you have a small plant you probably have little alternative but to wait
for some more growth. After a year or two growth should be enough to make a
distinction. The fact that S. alata is more often confused with S. flava is
an indication of the size difference.
Of course if you find you have S. rubra you will want to know what sub
species you are growing. But that, as they say is another story. :-)
-- Phil Wilson (cp@pwilson.demon.co.uk)