Saturday, March 12, 2011

Hoya campanulata lookalikes part1

Warning: This may be a bit dry for some people .....

There are 2 groups of Hoyas from SE Asia with white, waxy, bell-shaped flowers which has caused confusion amongst growers and taxonomists alike due to their apparent similarities and vendors applying errorneous tags without due diligence. The first is the Hoya campanulata group which appeared widespread in SE Asia and the second are from the wallichii complex which was collected mostly (maybe even exclusively) from Borneo.

Now let us examine the following 3 photos:

Vegetatively and in flower they look so different from other Hoyas and so similar to each other that one can almost be excused for thinking that they are one and the same. Even R.E. Rintz, who published an excellent early paper on Hoyas of Peninsula Malaysia, lumped them into a single species - Hoya campanulata.

Now, let's do some closeups of the corona ....

.... the top most plant has a rather fat and succulent corona (the star-shaped protrusion at the centre of the flower). It had been named Hoya wallichii for a very long time until it was recently deemed to be a separate species - H. danumensis, based on some subtle difference. This plant appeared to be confined to Borneo.

The lower 2 plants have slender corona and are collectively lumped under an umbrella called Hoya campanulata - although as I will show later, there appear to be more than 1 species there. This group has a wider distribution, from Malay Peninsula, Borneo, Java and Sumatra.

And here's a portrait of the real Hoya campanulata from Curtis Botanical Magazine, renown for accurate taxonomic depictions of many exotic plants collected all over the world during 1800s. The picture clearly shows the slender corona similar to the latter 2 plants here. It is taken from Simones' excellent web site.

So hopefully, we got these 2 rather different species sorted out.

I shall end this post by flashing another Borneo native that looked like a H. wallichii (or danumensis, take your pick) by virtue of the fat corona, and yet looked distinct in its smaller flatter corolla that curl backwards as shown below :

Any idea what is this ?


Mike Whittemore said...

Such great pictures! Thanks for sharing!

Wholesale Nursery Web Design said...

Wow! Such a superb pictures and i really really like it ..
Thanks for the sharing ..

Michele said...

Really nice article with great pictures!

In my personal opinion I may consider the observed variation in H. aff. campanulata and aff. cystiantha as natural infra-specific variation since the plant occur over a huge distribution but this may be up for discussion.


Hort Log said...

Hi Michele,
your opinion is shared by a few specialists I had talked to. But in the paper the difference between danumensis and wallichii is equally if not more trivial and yet it was accepted.

Michele said...

I need to add that the evidence of the difference between H. danumensis and H. wallichii have to be evaluated not just basing on my paper but also on the herbarium specimens examined as part of the paper. The picture of the corona of H. wallichii may not be very clear but it looks to me very distinct fron H. danumensis and H. campanulata. Anyway, one more paper to clarify the taxonomy of H. campanulata and H. wallichii is in progress.


Hort Log said...

Hi Michele,
Thanks for sharing. Do let me know if the new paper is published - I do believe there are much more to learn in this little studied section.

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