What is the difference between Aloe juvenna and Aloe zanzibarica?

Aloe zanzibarica is a synonym for Aloe juvenna. But just to confuse you, Aloe Zanzibarica is also a synonym for Aloe squarrosa.

I think this double synonymy is actually a point of confusion among the general public between juvenna and squarrosa, more than anything else. The record in the botanical literature (according to Aloes 2011 book) looks like this.

Aloe squarrosa = Aloe zanzibarica (obsolete) = Aloe concinna (obsolete)

Aloe zanzibarica Milne-Redhead was the replacement name for Aloe concinna (an invalid name) but in 1969 this plant was reduced to synonymy with Aloe squarrosa Baker (from Socotra). The original plant collected by Kirk from Arab traders was apparently not from Zanzibar but from the island of Socotra.

Now juvenna, a different plant from a different place, got into this mess not by any particular relationship to the above species, but because it is a lookalike for squarrosa, a much rarer and slower plant. If you see an aloe and aren't sure which of the two it might be, it's almost certainly juvenna. You kind of have to go out of your way to find squarrosa.

But because it's so common in cultivation, and so unfailingly prolific in the garden, juvenna (from Kenya and Tanzania) seems to have taken over the crown of Aloe zanzibarica in the public eye, at least on the interwebs. There's a page of so-called Zanzibar aloes here for example of which none are from Zanzibar and only 1 maybe is squarrosa. The rest are juvenna.



In the end zanzibarica is nothing but a historical artifact, best set aside in favor of the name Aloe squarrosa. But your plant is probably juvenna.

Hope that's clear!

Now I am really confused. According to wikipedia, succulent-plant.com, and many other sites, Aloe squarrosa (smooth, spotted leaves that curve backwards) is distinctively different from Aloe zanzibarica (shorter, non-recurved triangular leaves) which I am now led to believe is the same as Aloe juvenna.

Yeah that's what you'll find out there. I'd believe the book. They do lay out the entire story (as I presented it). Aloe zanzibarica was the one with the recurved leaves, now known as squarrosa.

Aloe juvenna (triangular leaves) was also known from cultivated material before its origin was determined. But it was found growing in a different place, on the west side of the Rift Valley in east Africa. Again not Zanzibar. Not even an island. That plant was named by Brandham and Carter, the same Susan Carter whose name appears on the Aloes book.

The original confusion that led to the naming of zanzibarica back in the day was when its origin was mislabeled in cultivation, very early on. That got corrected when the same plant (squarrosa) was rediscovered growing on limestone cliffs in western Socotra by John Lavranos, another author of the same book. They discuss zanzibarica twice in the history section, once about who collected it and once about the Socotra connection. Like I said, pretty much the whole story.

Based on the book that you cited, my plant was mislabeled as Aloe zanzibarica. It is in fact an Aloe juvenna plant. I am glad that that is settled. Thank you for your clarification.

Follow up on previous posts. I am now including a photo of my aloe (juvenna?) plant.

Very nice!

And now maybe I'll do some cleanup in the plant database.

Baja, Now add some more confusion to the mix. How's Aloe Minne Belle come in? Cultivar from Aloe juvenna? Just wanted your thoughts. And thanks for all the info.

I'm guessing that's a juvenna hybrid but have no actual knowledge on the subject. The leaves are longer and narrower than you would normally see on juvenna but it sure does look related.