Hoya vs Eriostemma

They seem so much alike so what is the difference?

Perhaps this could help

https://www.nparks.gov.sg/sbg/...

I don't understand the scientific stuff but Eriostemma is closely related to Hoya. The only visual difference I see is the size of the blooms. Eriostemma have much larger blooms than Hoya.

There are a few plants that used to be listed as Hoya but were changed to Eriostemma. I have Wax Plant (Eriostemma 'Ruthie') that I got years ago as Hoya 'Ruthie'.

Thanks @tofitropic!

All the genera formerly split from Hoya have been merged back into it.
Molecular genetics show clearly that that is where they belong. What is more perplexing is that Dischidia should also be nested within Hoya, but taxonomists seem not ready to do that.

Hortica said: All the genera formerly split from Hoya have been merged back into it.

The Catalogue of Life (which was updated two days ago) still shows Eriostemma as the accepted scientific name.

" Be aware that the COL Checklist is still incomplete and undoubtedly contains errors."

Well, it has been a long time ( 6 years ) since I did a deep dive into the current state of Hoya taxonomy, but this inspired a fresh look.

Most pertinent and insightful is this three year old paper:
Rodda, Michele, et al. "Phylogenetic studies in the Hoya group (Apocynaceae, Marsdenieae): the position of Anatropanthus and Oreosparte." Willdenowia 50.1 (2020): 119-138.
They do not accept Eriostemma, but do erect (agree with) the new genus Papuahoya. The genus Oreosparte is also supported.
They leave Dischidia intact. The rest of the genus Hoya in the widest sense, is still "problematic".

Also important is the two year old study:
Rodda, Michele, and Matti A. Niissalo. "Plastome evolution and organisation in the Hoya group (Apocynaceae)." Scientific Reports 11.1 (2021): 14520.
They seem to support resurrection of Clemensiella (which may include some of the putative Eriostemma). Their best quote: " Based on our results either Hoya needs to be separated in two genera, Hoya and Clemensiella, or Hoya needs to be more broadly circumscribed to also include species currently in Oreosparte. In this latter scenario Clemensiella, Oreosparte and Clade I (Group 1 and 2) of Hoya may be allocated to subgeneric rank."

A more recent paper by Odago, et al did not shed much new light:
Odago, Wyclif Ochieng, et al. "Analysis of the complete plastomes of 31 Species of Hoya group: Insights into their comparative genomics and phylogenetic relationships." Frontiers in Plant Science 12 (2022): 814833.
Wanntorp, Livia, Katherina Gotthardt, and Alexandra N. Muellner.

The promising sounding paper:
Baltazar, Alcona Mae P., and I. E. Buot. "Controversies on Hoya R. Br. Taxonomy." The Thailand Natural History Museum Journal 13.1 (2019): 59-68.
is nearly useless in my opinion.

So, it would seem some changes in the limits of the genus Hoya are happening, but a Genus Eriostemma is not one of them.

I think that the Hoya vs Eriostemma debate has parallels to the Philodendron vs Thaumatophyllum debate.

Gina1960 said: I think that the Hoya vs Eriostemma debate has parallels to the Philodendron vs Thaumatophyllum debate.

IMO that is a much clearer and easier split.

I didn't say it was the same thing. I said it had parallels. And no, some aroid botanists do not agree that the Thaumatophylums should have been split off from Philodendron.

Thank you to all the responders
I feel this may be a bit above my head but interesting reading

I am going with bigger flowers and maybe fuzzier leaves
and who knows I may still call them hoya and hope no one else knows for sure either.