Vol. 12, #5

November 1, 2012


                Hoyas aren’t the quickest to bloom of all flowering plants nor are they, as a rule, as showy as they are photogenic.  The gorgeous pictures taken and exchanged on various web pages and forums inspire a lot of  impatient, instant gratification generation collectors who quickly become disillusioned  and give up on them.  Many hoyas are slow to bloom and when they do bloom, their blooms don’t amount to a hill of beans.  The same can be said of a lot of other plants in a lot of other genera.

                    To keep ones interest in the hobby of growing hoyas, one needs to be a bit selective in choosing which ones to  collect.  If one is a scientist who is studying the genus (and on the payroll of a heavily endowed botanical garden), one would want to obtain every known species and continue hunting for more, but the average person, has limited space and, like me, long for flowers, preferably showy ones with delightful scents.  This inspired me to share a few experiences with you.


Blooming Hoyas


Hoya sp. from Kunming, Kina

Photo by C. M. Burton


Please pardon the mealies in the picture.  I didn’t see them until I put the picture here. Soon as I noticed them, I rushed out to the greenhouse and “Bayered” them.  No more mealies, at least for awhile.


1).  The  second “bloomingest”  hoya in my collection of about 200 hoyas is the one known as Hoya sp. from Kunming, Kina.  It’s the same one that some call Hoya revolubilis.  I’m not sold on that identification.  It just doesn’t fit the authors’ description.  I haven’t seen a holotype specimen but I have seen and photographed the flower parts of a second specimen cited by the authors as being the same.  The flowers don’t match, but the leaves are very similar.  I am also a bit confused  as to which hoya  is which as, Dr. Obchant Thaithong published a piece saying that she thought that Hoya revolubilis was merely a synonym for Hoya oreogena.   My plant was a gift from Berit Carlgren and came with pictures that appear to belong to two different species.  One of them has extremely long, very narrowly and sharply pointed leaf apexes on leaves that are about 2.5 to 3 inches long. That one’s flowers are bright yellow with red in the center.  The other’s leaves are about 8 to 9 inches long and their apexes are very obtuse.  It’s flowers are as white as freshly fallen snow.  This one is day-scented and the scent is heavenly.

        It doesn’t matter to me what this species is.  It is among the bloomingest things in my greenhouse.  Today (October 28, 2012), my plant has 14 umbels of flowers open. 


2).  IML-1778.  This is one of three that came to me labeled Hoya nabawanensis.  I’ve had the others much longer than this one.  They  haven’t bloomed.  I’ve had this one only a little more than a year.  Today (October 28, 2012) it has 5 umbels blooming.   I haven’t noticed any scent but suspect that it is one of the night scented ones.  One of these days, I’m going to skip a meal and a margarita and pay someone to put some lights in my greenhouse so I can spend some hoya sniffing time at night!




Above:  A picture of my IML-1778, which came to me labeled Hoya nabawanensis.


I had to cut those two umbels from the vine in order to photograph them.  They are best viewed from below.  This was hanging from a chain 8 feet from the floor.  The blooming ends of it reached almost to the floor.   All efforts to get those umbels in a position to photograph them from below failed.  The only way I could have photographed them from below would have required that I lie down on the greenhouse floor.  Had I done that, I’d have had to call 911 to come out and pick me up.  One thing I am sure of is that I did not mislabel this plant as the label put on it by David Liddle is still attached to it.




The picture on the left is said to be IML-1780. which I got from David Liddle as Hoya aff. nabawanensis.  Later on, David sent me two full page sets of pictures of it.  The label at the top of these pages reads, “ Hoya nawanensis, IML1780, Sabah, “  He misspelled the species name but there is no doubt that he meant Hoya nabawanensis.    The picture on the right was sent to me, by a friend,  with a cutting of what he said was the same species.  It was labeled “IML-1778 Hoya nabawanensis”.  This trader wanted to know which of these three is the “real Hoya nabawanensis.”  I wish I knew but I suspect that none is.  David Liddle identified the IML-1778 as Hoya nabawanensis.  He wasn’t infallible but after corresponding with him for nearly 35 years, I know that he was a careful researcher.  I don’t agree with all of his i.d.s but  I’d accept his identification before I would whomever it was that labeled the two lower pictures.  And what about the large umbel of pure as the driven snow flowers accompanying the Kloppenburg and Wiberg publication?

Adding to the confusion, I have another hoya that, when not in bloom, looks identical to IML-1778.  It has 5 umbels  of buds, which look identical to IML-1778 buds.  It came to me labeled  Hoya litoralis.


P. S.  Since writing the above paragraph (about 2 months ago, the one labeled Hoya litoralis has bloomed.  It is identical to IML-1778. 

When will all this mislabeling end and true identities to all our hoyas become a reality?  I am sure, not in my lifetime, but I hope that science and caring will make it possible for the next generation.  Before real science takes over a couple of  90 year old male chauvinist hogs,  who have hijacked the hoya naming and identifying process are going to have to meet their maker and leave things to people with more knowledge and less ego.


P.P.S.  I have  a stinking suspicion that David may have accidentally mislabeled the  ones I got as IML-1778 and as Hoya litoralis.   

        #3).  Hoya obscura.  This is probably the #1 “bloomingest” hoya of all.  I’ve had one hanging next to my east facing living room window for about 30 years.  It hasn’t been without flowers at any time since I put it there.  I have several other baskets of it out in the greenhouse.  None of them are ever without blooms.  I haven’t observed any scent on this one, either day nor night.


        #4). Hoya cumingiana.  This is another of those constant bloomers.  I have this one as IML-1330 and IML-1773.  


#5).  This unidentified one is too new to know whether or not it is a frequent bloomer.  It was a gift from a pen pal collector who lives in SC.  It came to me in September of this year, as a 4 inch long cutting.  It rooted quickly and has put on about an inch of growth.  It was labeled as NSV-406.  I don’t have a clue as to what the initials NSV stand for. This one might prove to be a frequent bloomer or it may never bloom again, but it rooted; made a peduncle and bloomed in less that a month.  The reason I place it among the “Blooming Hoyas  is because that umbel of flowers remained open and looked lovely for just over 3 weeks. None of the flowers on any of my other hoyas has lasted that long. This appears to be a clone of Hoya multiflora or one in that complex.


#6).  Hoya heuschkeliana (IML-904).  This is one of the miniature hoyas.  It’s flowers are yellow.  Its leaves greatly resemble those of Hoya bilobata. The flowers are not conspicuous, due to the yellowish green of the leaves,  but the plant is in bloom almost every day of the year.  I wish the pink flowered one bloomed so freely as the colour contrast of pink against those yellowish green leaves is very pleasing.



Hoya heuschkeliana


Note:  The leaves in the above picture are not Hoya heuschkeliana leaves.  The small section of vine came from an adjacent plant.  Look closely at the upper left and you can see where it entered and at the upper right you can see the tip of the vine.  Hoya heuschkeliana leaves are almost round.


        Maybe you have a hoya (not already featured here) that blooms frequently and you think it should be counted among the “Bloomingest Hoyas.”  If so, send me a picture and write a little piece about it.  Include source, source’s Accession #,  how long you’ve had it and whether you got it as a cutting or rooted plant; date of first bloom – or whatever you’d want others to know about it.  I’d like to feature a picture and  your comments here.  I’ll give you credit.




Hoya anulata Schltr.


        The Hoya anulata pictured here is IML-80.  I also grow IML-24, IML-84 and IML-1120.  In addition, I have pictures, given to me by David Liddle of  IML-138 (labeled Hoya microstemma) and IML-300.  I have several sets of photo-microscopic pictures of all the various flower parts of IML-80 and IML-1120.   I am convinced that all of these numbers represent Hoya anulata as the flowers match those in Schlechter’s illustration that is glued to his holotype specimen, which I have had the opportunity to see and make comparisons.  Although, David Liddle labeled IML-1120 as “aff. anulata,”  of all these specimens that I have seen, it appears to me to most closely match Schlechter’s holotype specimen.

                Yesterday (19 September 2012) I  saw a picture of these flowers on eBay.  It was offered for sale by Aristea.  It was listed as “IML-1120, Hoya anulata variegated.”  I have grown Hoya anulata-IML-1120 for many years.  I got it directly from David Liddle.  It matches Schlechter’s holotype and it is NOT in the least bit variegated.

        If Aristea has one that is truly variegated, I suggest that he, she or it, send a specimen to Cornell and publish it as a cultivar of Hoya anulata.  I also suggest that Aristea first take its plant to his, her or its county agent or local horticultural society’s plant disease experts who can diagnose what causes those light coloured spots on the leaves.  Those spots are NOT leaf variegation.  One suspected cause is bright noonday sun shinning down on the leaves, through glass (which magnifies the heat) on  drops of water, left on the leaves after watering  or misting the plant. Some harmful pathogens could also cause those unattractive spots but I  doubt that those spots  represent variegation.. 

        My only additional comment is, “I’m from Missouri!” * and I’ve had about 65 years experience growing and studying hoyas.


* To those of you who were born yesterday, the expression, “I’m from Missouri” doesn’t mean that I’m really from Missouri (I’ve never even been there).  It means, “I don’t believe a word you’re saying, have said, or are likely to say.”



Which Name is Correct?


                    Several of you wrote and asked me why people keep changing names as it is causing them much confusion.  The one name mentioned by each of them was the name Hoya ilagii  which they had heard was now called Hoya ilagiorum.  Each said, “Why won’t they just leave the names alone?    The answer is, “Because it is necessary to call a plant by its correct name.”  There is a Code which governs the naming of plants.  It says that when a species is named for a man  and that man was the one who collected the holotype specimen that “ii”  is added to the male’s name if his name ends in a consonant.  One exception to that.  If  his name ends in er, then only one “i” is added .   If the species is named for a female, and that female is the person who collected the holotype specimen, then “iae” is added to her name.  If the species is named for some person other than the collector of the holotype species, “iana” is tacked on the name.   If a species is named for several people (in the case of  this species, for an entire family), the name ending must be “iorum.”   So your pleas that they stop messing with the names should be instead, “If you are hell bent on publishing everything that doesn’t bite you, learn to spell and study the Code so you’ll get it right the first time.”   That was the advice given to me when I made a name spelling mistake years ago… I’m just passing the advice along!



What Are They,  Anyway?

Hoyas with a Lot of Names

Which Names Are the Correct Names?


        I’ve been re-reading many years of correspondence from David Liddle (starting with letters written to me in the early 1980s and continuing until about a week before his death).  It is interesting to see how his interest and level of knowledge of the genus grew over the years.  One was in species identification.  David appears to me to have started out as what we call a “lumper.”  A “lumper  sees one species where others see many.  David evolved into a “separator.”   He didn’t evolve into “the champion separator” that some others have become, but many of his identifications made during the last ten years of his life nullified quite a lot of those published by him and his friend, Dr. P. I. Forster prior to that.

        Most of us have, more or less,  assumed that the synonymy of species names, cited by various authors in the past, was correct.  I know I did until  both David and the late Hon. Douglas Kent questioned some of these things.  In one of the last letters I got from David, he wrote that he concluded, after studying original name publications and comparing the descriptions that the authors often had two different species in front of them and confused the two.  I think that likely when comparing fresh plant material with dried specimens but I usually wouldn’t  question an identification made with fresh material and a dried herbarium specimen if that  dried specimen had been collected (when it was a living plant) by the author of the name publication.  There are a few cases that I question (those of modern publications where I have first hand knowledge of both the authors;  their dried herbarium sheets and knowledge about  their collecting and record keeping habits).


Misidentifications #1 &  #2:   Hoya lasiantha and Hoya praetorii.


This is an obvious case of someone’s confusion.  I feel confident that all involved in publishing these two species (Korthals, Blume and Miquel) described the right plants but we moderns have mixed them and misinterpreted the authors’ data.  We also assumed that the lovely picture  (labeled Hoya lasiantha) in Curtis’ Botanical Magazine was accurately labeled.  I say that it was not.

Hoya praetorii  was first published in 1849 as Plocostemma pallidum Miq.  Hoya lasiantha  was also published then, as Plocostemma lasiantha.   When the Plocostemma genus was moved to the Hoya  genus in 1857, a new name had to be found for it as there was already a Hoya pallida.  The name Hoya praetorii  was chosen to honor  the collector of  the holotype specimen, Christian Frederik Eduard Praetorius.  The name, Plocostemma pallidum, tells us that the plant being pictured and sold, far and wide, as Hoya praetorii cannot be it because its flowers are very vividly coloured.  “Pallidum means “pale.”  There’s nothing pale about the hoya currently being circulated  in the US as Hoya praetorii.

Both, the late Hon. Douglas H. Kent and I searched in all the herbarium collections we could visit or borrow, looking for a type specimen.  We sent mail inquiries to all the other herbaria known to have hoya specimens.  No type specimens of this species was found so we had to rely entirely on the name publications to determine identity.

David Liddle was finally able to locate the holotype specimen, which R. Rintz had put in the Hoya lasiantha file, when he published his monograph in the Malayan Nature Journal ‘way back in 1977.  David said that the type of Plocostemma pallidum  was labeled as a Blume collection but this specimen was collected in Sumatra and Blume’s diary indicated that  he’d never been to Sumatra.  It is most likely that some other person is the one who misidentified that specimen as a “Blume sheet.”  Rintz, having been the last to use it and file it away in the Hoya lasiantha file seems to me to be the most likely culprit. R. Rintz’s publication showed Hoya praetorii to be a synonym for Hoya lasiantha, which simply isn’t the case.   I could be wrong and I apologize to Rintz if  he was not the one to mislabel that specimen.  As I see it, the Blume name on the specimen could only mean that the specimen was given to him by Praetorius, making it Blume’s property, not his collection.  Blume’s spelling the name with ii as the last two letters certainly says to me that Blume had named it for the collector of that type specimen.  One clue as to the collector of the Plocostemma pallidum type specimen is found in two places, 1). Praetorius collected in Sumatra  from 1830 through 1832 and also in Java (per  Regnum Vegetabile, vol. 109 Index Herbariorum Part II (5) Collectors).  Another clue is that the same publication does not show a single Blume specimen from Sumatra.

Another clue to the type collector of Plocostemma pallidum, i. e., Hoya praetorii  is found in Miquel’s  1856, Florae Indiae Bataviae.   This was the publication that moved Plocostemma pallidum  to the genus, Hoya.  Miquel cited the type as “Sumatra, in de wouden (Praetorius).”  That translates to. Sumatra, in the woods (Praetorius).”  Per the late, Hon. Douglas H. Kent, Miquel’s publication came out in several installments, beginning in 1856 and that this part wasn’t actually published until 1857).

One last piece of misinformation that I came across was a statement made by Mr. Kloppenburg, who alleged that  Sumatra, in de wouden (Praetorius)” meant that it was collected at a place named Praetoria in the woods of Sumatra.”  Friends, if it had been named for a place the spelling would have been “praetoriensis.”   There is no place on Sumatra named Praetoria and there wasn’t when this species was named.  If you don’t believe me, check these facts yourself… prove me wrong, if you can.  I’ll concede gracefully!




Hoya praetorii Miq.(syn. Plocostemma pallidum Blume)

Note the pale colour of the flowers




Hoya lasiantha Korth. ex Blume (syn. Plocostemma lasianthum Blume).

        The two pictures, above were sent to me by David Liddle as part of an article he had written about these two species.  He asked me to read the article and send him my comments.  He labeled the top one Hoya lasiantha  and the bottom one Hoya pallida.  After I sent him the facts I’d learned about them, he wrote to me and said:

“ I thought that your suggestion about Praetorius would bear fruit but it has not.  There was still a missing link somewhere as there are no Asclepiads listed at Leiden with him as the collector.  I went back through my old printed Leiden accessions and found the missing sheets of both species.  Hoya praetorii had been determined by Rintz in 1977 as Hoya lasiantha and was put in in the vouchers as such.  The type of Plocostemma pallidum (Hoya praetorii) is a Blume collection from Sumatra.  This collection data is probably wrong as by his diary, Blume was never there, so it is probably collected by either Praetorius or Korthals.  There is also the type of Plocostemma lasianthum  and a collection from Java determined by Koorders in 1908 as Hoya lasiantha.  This has made my day as I now know the sheets still existed at Leiden ten years ago and I have their old herbarium number.  Rintz strikes again.  I suppose after today, I now have more writing to do.”



Hoya lasiantha

        In addition to flower colour, there are several other differences between these two species.  The leaves of Hoya lasiantha are not nearly as broad as those of Hoya praetorii  and the corona lobes of  Hoya lasiantha are more spread out from the center.  They remind me of the male members of my family who have just finished Thanksgiving dinner and have pushed away from the table and leaned back in their chairs to take a nap.  On the other hand those of Hoya praetorii  are very close together. They remind me of a bunch of little old ladies sitting around a table, playing a card game.  They appear to be leaning  towards the center of the table, so as not to miss a word of dirt being spread about one of their missing friends.

        If the illustrations in several later publications are accurate, I believe that there are at least two other species in this “Plocostemma Section” that will show up one of these days.



The Brightly Coloured Leaves of Hoya obscura


Several of you wrote to me, commenting on a letter you had read on some Hoya Forum.  All of you said that someone had written a plea for anyone who had “the Hoya obscura variety with the bronze coloured leaves” to sell her a start as all she’d bought had plain green leaves.

My reply to those people is, “If that lady has a plain green leaf clone of it, she has the clone with the bronze leaves.”  The two are one and the same.  The leaf colour is entirely dependent upon environment.  The plant that has been growing in my east facing living room window for 30 years used to have those beautiful bronze coloured leaves but only on the side facing the window.  I wasn’t too diligent in turning the plant to give all sides the same amount of light so the outside was bronze; the inside was green.  Now that the dogwood tree I planted outside that window has grown tall enough to shade it, all leaves on that plant are green.  Before the tree became so tall, even the flower colour was affected by that light.  The half of the umbel nearest the window had peachy-pink flowers, while those facing the room were cream coloured.

I planted several pots of this one and put them in the greenhouse.    Below are a couple of their leaves.  You can see that these leaves  are two coloured.  The plain green portions of the upper leaf surfaces are where other leaves on the branches above them provided shade.  The beautiful bronze colour on the rest of the leaves’ upper surfaces is due to sun hitting the leaves and colouring them.



When the whole plant is viewed, all the leaves look as the lower portions of the two above leaves look.  One has to lift branches to see the green.  Of course, if only one side of the plant receives sunlight, the side away from the sun will be entirely green.  For uniformity, one needs to be diligent and keep turning the plant so that all sides will get enough sun to keep the colour evenly distributed or one could hang a grow light directly above the plant so that its rays hit all parts of the plant.