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A Rare and Wonderful Discovery: The Hunt for Philodendron petraeum

Dedicated to Julius Boos, Plantsman Extraordinaire and Investigator of the Meconostigma

Last Edit: 2010/7/29

Sometimes there are rare and wonderful discoveries to be found even in the most unlikely of places.

On June 28, 2005, I was studying about hemi-epiphytic aroids, and so I visited the New York Botanical Garden to take pictures of any and all aroids that featured this life habit, and thus perhaps assuage my then obsession with these fascinating plants.

Out of the dozens of pictures of aroids that I took, one of the most interesting was an arborescent specimen with large beautifully glossy triangular leaves. Unfortunately, the specimen was labeled as being an unknown Philodendron.

I believe I had not yet become a Meconostigma nut at the time, but the aroid was sufficiently impressive that I submitted the image for identification to the Aroid Identification Center in July of that same year.

There the image languished for 2 years, until March 31, 2007, when Julius Boos, who at the time was tracking down specimens of the rather rare P. williamsii, sent an email to Ron Weeks and Dr. Tom Croat saying that the plant in the NY Botanical Garden may be P. williamsii.

Julius contacted me about it on April 2, 2007, asking whether I could send Tom a bigger image of the unknown aroid in order to see whether it was a mature specimen of P. williamsii. However, Tom said it looked like P. undulatum instead, and Julius concured, but got information on whom to contact at the NY Botanical Garden.

The Curator of Glasshouse Collections at the botanical garden, Marc Hachadourian, wrote Julius back on on May 14 and identified the specimen (labeled as accession number 1048/93A Philodendron) as having been received from a Mr. Conrad Fleming of the St.George Village Botanic Garden in Fredricksted, St.Croix.

Unfortunately, the trail towards identifying this aroid became rather cold at that point. When Julius talked to Conrad in June of 2007, the original donor replied that he had gotten it from Fairchild Gardens in Miami. Mr. Fleming, however, was not able to provide a definitive answer about the origins of the plant. Steve Lucas, a friend of Mr. Fleming, later relayed to me his opinions about it:

philodendron minarum.

Click on thumbnail above for Hi-res detailed image. From Alfred B. Graf's Exotica Series 3 (vol 1, 7th edition), p 186

"Julius wrote me months ago regarding this Meconostigma at New York that came originally from me. I can't say that I have any clear recollection as to what it may be. It certainly does look like undulatum. The only thing wrong with that theory is that, as far as I know, I never did distribute undulatum. I do have that sp., which I collected decades ago in the northern reaches of Mato Grosso, Brazil and I do still have that one plant in cultivation, but as far as I know I never had extras for distribution. But who knows, maybe I did! I more incline to the theory that I gave NYBG a cutting of Philodendron "minarum" (this was the name on the label at Fairchild), which, I think, is quite similar to paludicola, which is a sp. I've seen in cultivation but do not currently have (I got it from a nursery in Miami, but for some unaccountable reason, it died soon after arrival here). I do still have that Fairchild "minarum" in my collection and its leaves are certainly not as divided as the plant in the photo."

Meanwhile, other avenues of inquiry also dried up. Ron Weeks, who owns an extensive collection of rare aroids, reported that he did not have anything like it in his collection, and neither did Fairchild Gardens, which may have lost the specimen in one of the many hurricanes that periodically strike Florida. Leland Miyano, who was already a friend of Julius at the time, also could not name the species.

It was at this point that the hunt could have prematurely died, and again that image of the unknown Philodendron languished for another two years, until a post I made at the UBC Botanical Garden Aroid Forum and an email sent to Julius on May 8, 2009 re-invigorated the search.

Steve Lucas, another hard core aroider who frequented this Aroid Forum and hosted a fantastic site called Exotic Rainforest, started querying his various acquaintances about its identification, even going so far as to get Mr. Conrad Fleming into recounting his memories about the donation.

He also emailed Eduardo Goncalves in Brazil, who has been studying aroids, and who had published a seminal work on the current taxonomy of the subgenus Meconostigma in the journal Aroideana 1. Eduardo replied:

To me, it is Philodendron petraeum, which is common in boulders and limestone cliffs of Southwestern Brazil and Paraguay. I am not sure if this form (that has more divergent posterior lobes and smaller lateral lobules than P. undulatum) will prove to be the same as P. undulatum (as Simon Mayo pointed out), but considering that the region is poorly known, I am still considering them different. I am waiting for a DNA study to be sure.

Armed with Eduardo's tentative identification of the unknown aroid as Philodendron petraeum, I quickly managed to get the original references.

Philodendron petraeum Chod. & Visch.
in Bull. Soc. Bot. Geneve, 1919, Ser. II. xi. 296 (1920).

I also found out that Rutgers University had a copy of this very journal in their Busch Annex, and so I resolved to visit the university post haste in order to delve deeper into the origins of our unknown meconostigma specimen.

In the meantime, a quick look into Simon Mayo's 1991 revision of the meconostigma 2 gave us more clues about this putative species.

Simon treats P. petraeum as an "incompletely known species", with three different variants and the type being in Paraguay. He states:

I have not studied the type material of any of these taxa, which except for var petraeum is known only from sterile plants. The species has sagittate leaves, a rupicolous habit, the spathe as long or longer than the peduncle and a 6 locular ovary according to the description. In var tobatiense the leaves are larger, up to 50 cm long and 40 cm broad. Var triangulare and valenzuelae both have smaller glaucous leaves which are triangular in the former and relatively narrow in the latter.

The available information suggests that P. petraeum is a distinct species since it does not appear to fit any other described taxon. Though superficially similar to P. corcovadense, Chodat and Vischer's fig 262 shows stems with \very contracted internodes. These taxa are cited in Croat and Mount's recent treatment of Paraguayan Aracea

Photo by Hernan Fernandez that Leland Miyano found on Flickr.com

Meanwhile, as sometimes happens in real life, clues from disparate threads started intruding into the story. On May 12, Leland Miyano, a renowned landscape designer and author from hawaii, excitedly pointed out that while perusing Flickr, he had inadvertantly stumbled on an aroid that looked eerily like a mature version of the unknown Philodendron.

And in another wonderful example of synchronicity, it just so happened that I was ALREADY in contact with the photographer (turdusprosopis aka, Hernan G. Fernandez) because I was asking him about another plant of his, and Hernan, a naturalist with an eye for photography, was only too willing to help us in our endeavor.

Hernan's photo notes that the image was captured in the Inta Delta. Partido de Campana, provincia de Buenos Aires, ARGENTINA. (9 de abril de 2008). He elaborated on it:

The plant of this photograph is next to a large group of plants of this species. These are wild, but it could be an invasive species there. Grow on a site which is covered by water several times a year, although still only 1 or 2 days flooded and then the level of water decreases. These plants live just 5 meters above sea level; in silt and clay. Rocks are not found in the Parana river delta.

The exact geographical location is:
34°10' 29.72'' South 58° 51' 38.80'' West

I run the coordinates through Google Earth, and found that the aroid is located about 60 km north and west of Buenos Aires, near the river and very close to a canal. There are fields to the east of it, and what look like houses or storage areas to the west.

The location of this Philodendron is very close, if not at the boundary of, the southernmost expansion of the genus, which excited all of us, and prompted Julius to recount stories about other mecos that were sighted only slightly north of that area.

Location of Hernan's Philodendron, 60 km north and west of Buenos Aires, Argentina

Meanwhile, I finally managed to visit Rutgers University on May 19, and made copies of the relevant paper 3, scanning them into PDF format and then distributing to Julius and Leland. Although the article was in French, and the actual plant description in latin, the article did provide some interesting images and drawings of the putative Philodendron petraeum, which I have posted below.

Click on thumbnail above for Hi-res detailed image.
Image from Chod. & Visch. (1920)

Click on thumbnail above for Hi-res detailed image.
Image from Chod. & Visch. (1920)

I decided it was time to take more detailed pictures of the original plant, and on May 21 I emailed Francisca Coelho, Director of Glasshouses at the NY Botanical Garden, for permission to go close to the unknown Philodendron to take photographs. This was necessary because the aroid was located in the middle of a group of plants, away from the walkway. Ms. Coelho was gracious enough to respond quickly, and we set a date of May 28 for the viewing.

As it happened, May 28 was a drizzly day, and I soon encountered other problems besides the rain. Now, I usually do not travel to NY City, and when I do, I usually go by the Holland Tunnel, so this was one of the few times when I had to travel via the George Washington Bridge. Unfortunately for me, I had no idea about the amount of traffic that normally accumulates on and near the bridge, and the rush hour congestion that greeted me that day was horrendous. I used my blackberry to email Francisca and update her on my progress, and it was not until 10:45 am (45 minutes late!) that I managed to get to the botanical garden in the Bronx.

I met Francisca at the tropical rainforest area at the Enid A. Haupt Conservatory, and we quickly made our way to the aroid, which was located near a metal stairway. After I had taken several photographs of the aroid, Francisca took me on a short tour of some other parts of the conservatory, including several specimens of the genus Aristolochia, tropical vines which had some very bizzare flowers that were pollinated by flies.

We also took a look at an impressively large meconostigma that was labeled Philodendron undulatum, and which was slowly climbing up what I took to be an enormous fallen and arched tree trunk, but which Francisca noted was actually made of concrete. On the opposite side of the concrete tree trunk, an equally large Philodendron goeldii pressed itself against the glass of the conservatory, perhaps in hopes of catching more sunlight. Francisca said she had moved both mecos from restrictive pots to their present locations in the 1990s. I mentioned that the meconostigma specimen labeled P. undulatum did not seem to be that species. It had the bipinnatifid leaves of P. bipinnatifidum, and it lacked any persistent intravaginal squamules on those parts of the basal stem that I could see. Francisca groped around the trunk of the aroid and finally fished out a really old looking metal tag, which named the specimen "Philodendron eichleri", and noted that it had been donated in the 1950s.

It just so happens that there had recently been some controversy about the status of this taxon, with people not sure whether it is a hybrid or a species. It is however, currently made synonymous with P. undulatum by Simon Mayo, which explains the current label for that specimen. I'll note for those who are curious that the NY Botanical Garden specimen had a bloom, and that I am hoping someone in the garden can take a picture of the bloom when open, and perhaps preserve the inflorescence in alcohol for further study once it has passed.

The hi-res pics that I took during my visit are posted below. The original were 4000 pixels wide, but I have modified them to 2000 pixels wide for bandwidth reasons.

Click on thumbnail above for Hi-res detailed image

Click on thumbnail above for Hi-res detailed image

Click on thumbnail above for Hi-res detailed image

Click on thumbnail above for Hi-res detailed image

Click on thumbnail above for Hi-res detailed image

Click on thumbnail above for Hi-res detailed image

As can be seen from the hi-res photos, this meconostigma has persistent intravaginal squamules all the way down towards the base. These are about 3-5 mm in length, the length sometimes up to 4x longer than its width at the base. They look like small sharp pointed alligator teeth! You can, with some strength, break one off, but not easily and not from the base, which seems to be strongly attached to the larger stem.

The width of the stem is approx 8 cm., the width of the leaves is between 50-60 cm, and the leaves have lengths of between 60-70 cm. The dorsal surface of the petiole looks similar to that of P. bipinnatifidum, with a distinct canal running along the surface.

On May 30, after reviewing the new Hi-res images from the NY Botanical Garden, Julius summarized his current thoughts for us:

I have thought, searched, read and contemplated this puzzle, and will give my opinion and speculations about this plant and its poss. origins. These seem to parallel those of Simon, and might help explain Lelands points in his note (below), but we must leave this to people like Eduardo or someone at Kew or MOBOT who just MIGHT have what it takes to do genetic work, this MIGHT reveal the parentage/true origins of P. petraeum and P. undulatum.

To ME based on distribution, there seems to be a ''good'' species (P. undulatum) with its extra-long, spine/thorn- like intravaginal squamules and shallowly sinuate leaf blades (not deeply lobed), this species/var seems to occur further North. Then we have the P. petraeum "complex" which seems to occur further South, as far as the line limiting the distribution of the genus Philodendron in S. Argentina/Uruguay/Brazil (Hernan's plants), and the plants illustrated in Chodat & Vischer, AND the plant illustrated in Croat & Mount.

The illustration in Croat & Mounts is of particular interest to me, as it illustrates a leaf with not only a sinuate blade margin, but quite deeply lobed, 4 - 10 cm. deep according to their key (look at the illus. on Pg.26, top left, the r. side of the drawing of this leaf blade). They also do not discuss the length of the squamules, a notable feature of what we now consider a real important feature of the species P. undulatum, nor are they indicated in their illus. of the rhizome/whole plant. Croat & Mounts illus. somehow seem to be "saying" to me that this plant has some P. bipinnatifidum in its parentage, and the description of several "vars" by Chodat & Vischer based on the different shapes of the leaf blades on individual plants (as mentioned by Simon Mayo in his excellent work on the Meconostigmas), who also suggests and makes a pretty strong case for these plants being of hybrid origin). Simon also illustrates his concept of P. undulatum as having leaves with a sinuate and not deeply lobed margins.

All of the above brings me to my purely speculative ''opinion'' that at least the Southern P. petraeum, (the plant at N. Y. Bot. garden seems to "fall" into this group) is probably of hybrid origin.


The images below show the form of P. undulatum that is currently most associated with this species. It has truiangular leaves but very long but sparse intravaginal squamules.

Philodendron undulatum.
By Leland Miyano.
Philodendron undulatum.
By Leland Miyano.
Philodendron undulatum.
By Brian Williams.
Philodendron undulatum.
By Brian Williams.
Images from Leland Miyano and Brian Williams of typical Philodendron undulatum showing sparse but very long spine-like intravaginal squamules. Click on thumbnails above for Hi-res detailed images.

I'll add the following:

If we proceed on the basis of Eduardo's 2002 revision of the Meconostigma, where the species Philodendron undulatum is identified by the presence of "stems with long and thorn-like intravaginal squamules" 1, then it is obvious that this unidentified aroid in the NY Botanical Garden is not this widespread and problematic species.

Indeed, it should be noted that Simon himself comments that "Further collection and field study in the drainage system of the Rios Parana and Paraguay is needed to clarify the definition of P. undulatum." 2

It may be that P. undulatum is in fact composed of several cryptic species (and possible hybrids), and that the specimen in the NYBG may indeed represent the murky P. petraeum group, whether as a full species or a hybrid. Further genetic studies may elaborate on the distinctions between these species.

I'll end at this point by displaying an image of the stem of the syntype of P. undulatum from Rio. Janeiro et Minas. As can be seen, the stem is seemingly covered with a large number of small (less than 1 cm long) persistent intravaginal squamules.

Philodendron undulatum Engl., Syntype. Brazil: Rio. Janeiro et Minas. 1887, Leg.: A. Glaziou 16503.. From: Röpert, D. (Ed.) 2000- (continuously updated): Digital specimen images at the Herbarium Berolinense. - Published on the Internet http://ww2.bgbm.org/herbarium/ (Barcode: B 10 0247019 / ImageId: 252334) [accessed 23-Jul-10].

UPDATE 2014-7-23

On July 2014, I again visited the New York Botanical Garden to check on the unknown Meconostigma. It was still there, though it did not seem to have as many leaves as earlier. I have asked the garden to inform me when the Philodendron blooms, so hopefully there will come a time when I can place here a detailed image of the inflorescence of this fascinating aroid.

Philodendron petraeum.
Philodendron petraeum.
Philodendron petraeum.
Images from from July 2014. Click on thumbnails above for Hi-res detailed images.


1 E.G. Goncalves and E.R. Salviani (2002). New species and changing concepts of Philodendron subgenus Meconostigma (Araceae). Aroideana 25:

2 Mayo S. (1991). A revision of Philodendron subgenus Meconostigma. Kew Bulletin 46(4): 601-681

3 Chod. & Visch. (1920). Aroidees. Bulletin de la Société Botanique de Genève. Geneva. Ser. II. xi. pp 255-299



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