From Bluebonnet Swamp Nature Center in Baton Rouge, La.
We seem to have two species of Water Primrose growing around a small, sunny pond.
I can't find anything to distinguish type A from Type B except that one has bigger blossoms, longer leaves and longer seed pods.
Both have flat sided stems.
Leaves and stems of both types start off green and turn red as they get older.
Actually, I think Ludigia decurrens Walt - Willow Primrose (or upright primrose, or wingleaf primrose-willow, or primrose-willow) is what I have been calling Water Primrose A - the one with smaller flowers, smaller seed pods and smaller leaves.
See the attached image for why it is sometimes called "wingleaf primrose-willow".
The seed pods for Ludigia decurrens Walt are listed as being 3/4 to 1 inch long, like Water Primrose A.
Thanks for the help, Moon/Jean.
I was hoping there was some miscommunication.
Thanks for the links to Louisiana rare species list too.
For Shrubby Water Primrose, Mexican Primrose Willow - Ludwigia octovalvis,
it is often mentioned that it has woody stems or is woody at the bottom.
One of ours is very woody with the "stem" almost 1 inch in diameter at the bottom.
(See image attached to this message.)
I am pretty comfortable that Primrose A is:
Ludigia decurrens Walt - Willow Primrose (or upright primrose, or wingleaf primrose-willow, or primrose-willow)
And Primrose B is:
Ludwigia octovalvis - Shrubby Water Primrose, Mexican Primrose Willow
(This is the one with bigger blossoms & longer leaves and longer seed pods.)
I will post it as solved
But others can still feel free to pipe up with other opinions/comments.