Confusing Sennas
I propose to fix the identification of these Senna observations:
Observations of Senna × floribunda misidentified as Senna corymbosa
https://www.inaturalist.org/projects/senna-cultivar
All these observations need to be identified as Senna × floribunda.
Senna × floribunda has leaflets with end in point.
Observations of Senna septemtrionalis misidentified as Senna × floribunda
https://www.inaturalist.org/projects/senna-septemtrionalis
All these observations need to be identified as Senna septemtrionalis.
Senna septemtrionalis has acuminate leaflets.
This publication explains the details and the origin of the confusion:
CONFUSING CASSIAS
Susyn Andrews, Sabina Knees
CURTIS'S Botanical Magazine
Volume 5, Issue 2
May 1988
Pages 76-82
In short, the rationale is:
- Senna × floribunda has been sold under the name Cassia/Senna corymbosa, initiating the confusion. (See for instance this observation of a Senna × floribunda sold with a Cassia corymbosa label).
- In La Réunion, some web sites report the presence of Senna × floribunda, but not that of Senna septemtrionalis, resulting in a generalized misidentification of the observed Senna septemtrionalis as Senna × floribunda, further propagating the confusion.
Based on the leaflet shape and the distribution of extrafloral nectaries (between the leaflets of all pairs, except the most distal pair where EFN may be present or absent), Senna septemtrionalis cannot be confused with any other Senna species. Same remark for Senna × floribunda, it cannot be confused with any other Senna. The "CONFUSING CASSIAS" publication clearly explains and illustrates what is what, and on this basis there is no confusion possible for identifying the observations of these Sennas on iNaturalist.
Comments
@jf920 @oxalismtp @arboretum_amy @picklejar
Would you like to help me fixing these identifications?
(I can send you a copy of the publication referenced above).
Hi @jeanphilippeb ! That sounds great!
Let's go!
Some web sites say that Senna × floribunda would be an hybrid of Senna multiglandulosa and Senna septemtrionalis:
https://www.mi-aime-a-ou.com/senna_x_floribunda.php (with photos of Senna septemtrionalis, propagating the confusion with this species in La Réunion)
https://tropical.theferns.info/viewtropical.php?id=Senna+%C3%97+floribunda (saying it is widely naturalized in the tropics and subtropics, yet it is not observed wild on iNaturalist, except maybe this observation of a possibly escaped individual, in Mexico).
The midrib aspect of Senna × floribunda, looking like a groove, is similar to Senna multiglandulosa (not a common Senna character).
The extrafloral nectary shape of Senna × floribunda is similar to Senna septemtrionalis (and to several other species).
Beside this, all three are very different.
Senna multiglandulosa pistil is hairy (not a common Senna character).
Senna septemtrionalis has less pairs of leaflets, and acuminate leaflets.
Up to 4 different IDs for this observation, consistent with the species involved in the confusion reported.
Thank you for taking the time to post this information!
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