# Ludwigia peruensis vs Ludwigia Glandulosa (sp 'Peruensis')



## pweifan (Jun 23, 2007)

This question is aimed at Cavan, but I thought the world would be interested, so I'm posting it here.

What is the difference, if any, of Ludwigia peruensis and Ludwigia glandulosa and Ludwigia glandulosa sp 'Peruensis'?


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## Cavan Allen (Jul 22, 2004)

There is and has never been a "Ludwigia peruensis". Possibly, that name is in reference to the - relatively - unrelated _L. perennis_. See this reference at Kew:
http://www.theplantlist.org/tpl/search?q=ludwigia

Even if it were a synonym or something like that, it would be on that list one way or another.

Sp. is used when a species is not known, so it's not really correct to use it along with a species name. When a cultivar or a plant from a certain place is indicated*, single quotation marks are used instead. For example, you might say _Rotala mexicana_ 'Araguaia" but not Rotala mexicana sp. Araguaia. That sp. in the second example is totally superfluous.

So to answer your question, it's really all just _Ludwigia glandulosa_. There's also _L. glandulosa_ subsp. _brachycarpa_, which is a smaller plant with narrow leaves native to Oklahoma, Texas and western LA, but that is not yet in the hobby as far as I know.

* It would perhaps be better to write that as *Rotala mexicana from Araguaia* to differentiate it from anything that might be an artificially selected strain or cultivar.


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## pweifan (Jun 23, 2007)

Thank you, Cavan.  It helps a lot to understand how naming works. So L. peruensis is yet another name that means nothing that made it out in the wild? That's good to know. I saw a tag that said "Ludwigia grandulosa" at PetSmart (probably a mashing up of names with L. grandiflora). The best part is it wasn't either of them, it was L. repens x L. arcuata 

I find Ludwigias interesting the way a lot of hobbiests find cryptocorynes interesting. I like how they can hybridize (is that a word?) and still be beautiful.

Thanks again.


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## Cavan Allen (Jul 22, 2004)

Apparently, that name is just made up. It has never been formally published anywhere and is not listed as a synonym of _L. glandulosa_. How did it take hold? I've got no idea.

Yes, I find them interesting too. And hybridize is a word. 

Many of the species (as is common in plants), in fact, were formed through hybridization. It's some really neat stuff. The even neater thing is that for our purposes, all the hybrid combinations are new plants. Sections (groups within a genus of closely related plants) _Dantia_ (repens, palustris, brevipes, arcuata and spathulata) and _Microcarpium_ (glandulosa, sphaerocarpa, etc) are now combined in section _Isnardia_, and in the US, there are 18 species. Nearly every combination is possible, and it happens a lot. You could probably tinker the same way that people do with _Echinodorus_, but, perhaps fortunately, for confusion's sake, that hasn't happened yet.


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## Lusher (Apr 19, 2013)

Sciencetific name are so difficult to memorize. But good thing they exist.


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