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Re: ludwigia glandulosa/peruensis?



Arthur asked about ludwigia glandulosa/peruensis, he thinks they might be
the same plant.

Are you sure you don't mean Ludwigia perennis?

The species epithet "peruensis" doesn't show up in the Index Kewensis or the
Gray Card Index in connection with the genus Ludwigia (in other words, there
probably isn't a plant called "Ludwigia peruensis").

The name "Ludwigia perennis L."  refers to a species which grows in India.
It was first used by Carl Linnaeus in Species Plantarum, published in 1753.

"Ludwigia glandulosa Walt." is an American species - there are many web
references to it growing in Tennessee and several other states. I haven't
found out WHEN the name was first used, but several subspecies have been
described variously in 1944 and 1986.

Tropica sells Ludwigia glandulosa (''perennis'') and claim that the plant
was at one time sold under the name Ludwigia perennis. The illustration they
give indicates that it is a pretty red plant. Their reference for plant
names is C.D.K. Cook, who wrote several books - the Aquatic Plant Book and
Aquatic and Wetland Plants of India being two that I know of. I have the
first one, but there is very little information in it at the species level.
Cook's book on Indian aquatics might have some information on Ludwigia
perennis and its natural distribution in India.

Many aquatic plants have very wide geographical distributions, but I find it
hard to believe that a plant native to India is the same species (even if it
was described under a different name) as one found growing in Tennessee,
unless it was introduced there. I don't think that the aquatic plant hobby
was developed enough in the 1940's to make it very likely for that to have
happened.

I have seen references on the web for "Ludwigia peruensis", but they are all
aquarium hobby related sites, either individual hobbyists or companies
selling aquarium plants. I don't put much faith in either as far as plant
names goes, and suspect that it isn't a valid name. If you got the name off
of a Japanese hobbyist's site, I'd suspect a mistake in the use of the name.

James Purchase
Toronto