Natural Variation and Ontogeny
Neither is difficult to understand but both require an explanation.
Why you may find it difficult to identify the species of a plant.

Is it natural variation or morphogenesis that causes the leaves
to appear different within the same plant species?

"Much of what we believe is based on what we have yet to be taught. Listen to Mother Nature. Her advice is best."
Every leaf of the same species does not have to look alike!

My sincere thanks to my mentor, noted aroid botanist Dr. Thomas B. Croat Ph.D., P.A. Schulze Curator of Botany of the Missouri Botanical Garden in St. Louis, MO., to aroid expert and friend Leland Miyano in Hawaii, my friend and aroid expert Julius Boos (1946-2010) in West Palm Beach, FL as well as my friend Joep Moonen (yupe) who is a noted naturalist and discoverer of many plant species in French Guiana.  I enjoy reading their notes, journals, texts, virtually daily emails as well as  listening to their personal advice.   Without their counsel this text could not have been written.

Text by Steve Lucas, www.ExoticRainforest.com

Ontogeny and natural variation

The plants in a rain forest commonly assume many "faces".  The face of a plant is its leaf and the leaves of a single plant species may take on a variety of forms.  Although sometimes difficult to accept, the leaves on a single specimen can take on a variety of shapes and those forms are the result of two different natural processes: Ontogeny and Variation. 

In the plant kingdom a species is a taxonomic unit or a group of individual organisms that share common characteristics.  Those characteristics makes a species distinct since they possess a quality separating them from other groups of plants.  All of the species that have a certain number of characters in common are grouped into a genus such as Philodendron, Anthurium, Epipremnum, Caladium, or any defined other genera. 

It is certain that over time nature has chosen to create new species as a result of both natural selection and natural hybridization where two existing species have cross pollinated.  Eventually, perhaps over thousands of years, those natural hybrids produce a stable cross which scientists now consider a "species". 

A natural hybrid that persists in nature is created when the pollen of one plant species is applied by an insect or other pollinating animal to the female flowers of another species that has enough genetically similar characteristics in their mutual DNA to produce viable offspring that can also reproduce.

We call the changes to the shape of a plant that occur during its life cycle morphogenesis, but the scientific name for the "morphing" process is ontogeny.  Ontogeny is the natural changes observed during the life of any living organism that includes the way the leaves on a plant change from the juvenile to the intermediate blade shape and finally into the adult leaf form.  The second process is known as variation and that process can cause a great deal of confusion, especially among plant collectors. 

Just look at the photos to the right and left above.  Every photo is of the common house plant "Pothos", Epipremnum aureum  and each was taken on the same plant!

Think of ontogeny as the progression of the changes you see during the life of a child.  As children grow they continuously change in appearance.  Just look at your own childhood photos or those of your grown children and you are looking at the changes science knows as ontogeny.  Although we tend to believe the leaves of any plants species must look alike those changes can be dramatic.  

There is another change within many plant species that is much slower but is still just as constant, those changes are known as variation.  In science, variation could be defined as an organism that is not constant in appearance, possesses the ability for a variety of populations. or a plant organism that can change or mutate a physical characteristic over time.  Leaves and other characteristics don't always have to look alike.

This page shows photographic evidence of the variation within collector grown plants as well as species photographed in nature.  Since those differences can often be observed on a single plant the concept of variation can be very confusing to anyone that refuses to accept the scientific principle.  The goal of this article is to simplify your understanding of both processes involved.

A study by Purdue University scientists may be closer to identifying a gene responsible for high sodium levels in some plant populations.  That study may possibly have applications for understanding a wide variety of properties that may include natural variation. 

Natural variation within a species is a well known scientific subject and is frequently written about  in scientific literature.  You can easily locate these scientific articles on the internet but most are very technical.  Even Charles Darwin (1809 -1882) made a study of variation and published his findings in 1859 as a result of his five year voyage around the world.  Darwin's theory of evolutionary selection holds that variation within species occurs as a random process and the survival or extinction of each organism is determined by its ability to adapt to its environment.  Whether you accept his theory of evolution is immaterial, natural variation is proven in botanical science. 

Aroid variability

Since this website deals primarily with members of the family Araceae, commonly known as aroids including Philodendron, Anthurium, Monstera, Alocasia, etc., the discussion in this article will concentrate on species within that group.  However, these principles are applicable to all plants.  The problem that occurs is many plant collectors don't understand or refuse to accept the science of variation as it occurs in plant species.  As you will read, many of the plants some of us insist are different species are one and the same plant.

In his A revision of Philodendron subgenus Meconostigma (Araceae), Dr. Simon Mayo of the Royal Botanic Garden Kew in London states, "Philodendron is a genus of outstanding horticultural importance and subgen. Meconostigma includes some very well known ornamental species. P. bipinnatifidum (syn. P. selloum), one of the world's most ubiquitous houseplants, has provided a rich source of variation for the breeding of different foliage forms"

Some may contend since variability is not easily visible or noticeable it does not exist. Variation is not only common, if you are a plant collector it is almost certainly all around, the chances are you simply had no idea what you were observing.  Just look at the photo comparisons in this article and you will likely realize you see variable plants all the time.

Aroids are a group of highly variable species.  The commonly grown landscape plant Caladium bicolor has over 40 known synonyms (same plant, other name) and at least 40 known variations due in part to its vast range of color.  In volume 2 of the 1987 issue of Aroideana, published by the International Aroid Society, botanist Dr. Josef Bogner wrote in an article entitled Morphological Variation in Aroids, "The Araceae or aroid, are a large family of about 2400 species, grouped in 107 genera and these again in nine subfamilies. The aroids are mainly a tropical family and are distributed world-wide. They show great variation in their morphological characters, which will be described in this paper along with some other data." Since that writing the aroid family has grown closer to 3300 species in 116 genera. 

Aroids are plants that reproduce by growing an inflorescence that contains a modified leaf known as a spathe surrounding a spadix. The spathe is not a "flower", but is instead a modified leaf whose purpose is to offer protection to the spadix at its center.  During sexual anthesis there will be found very tiny flowers on the spadix when the plant is ready to produce seeds.  

You can learn more about aroid reproduction at this link.

You can find variation in many plant species.  Tropical plants now make up a huge number of specimens that are kept as "house plants" so don't expect every plant you buy to look exactly like another specimen of the same species!  Aroid species include highly variable specimens in almost all genera. 

Plants vary not only in their leaf shape but also their color and other plant characteristics.  Simply because two plants that are the same species produce leaf blades with a different color on either the top or the bottom does not mean they are a new or different species.  Dr. Croat wrote in a personal communication, "Color is like any other single character. It can be critical or not depending on the species. There are species where the spathe color or spadix color is variable and of course leaf variegation is notoriously unreliable at the species level. Still, most species reproduce pretty true to their parents and color at any given stage of development is generally quite reliable."

The differences argued by collectors in the inflorescence normally involve color or variations in the shape of the leaves or the spathe but both can be variable and cannot be relied on to determine the species of a living plant.  The spathe of an aroid can easily change color in some species and in other cases two specimens won't produce identical spathes or spadices.  Although collectors frequently believe a variegated specimen is a different species, as Dr. Croat points out, variegation is unreliable as a species determination.

 Color can however be an indicator leading you to the determination of a specific species.  Philodendron erubescens normally has a reddish stem with reddish petiole and cataphyll but even those can be green.  Color can be important in some instances but not when there are no other characteristics to support the claim the plant is a different species.

If you have more than a few plants in your collection it is likely you own some that are natural variations of the same species.  The chances are likely you are assuming some of them are different species because the top or bottom of a leaf may have a slightly different shape or color but to a botanist some are still one and the same plant.  In fact, the leaves of an aroid can be dramatically different as you will see in our photos. 

The geographical effect

Variability has been established in many papers on Araceae including explanations of how the geographic location of a specimen can affect its shape.  In a scientific paper by Dr. Tom Croat (credentials at the top of this page) and Monica Carlsen entitled Taxonomic Revision of the Section Semaeophyllium, you will find, "Size of any morphological structure in Anthurium is highly variable because plants often change remarkably in size over the course of their lives and also in response to the general climatic conditions where they occur, particularly in geographically widespread species".  Monica and Dr. Croat make it clear in the text the size of the leaf, the size of the spathe as well as the size of almost any feature of any aroid can be variable for a variety of reasons which includes where the plant exists in nature. 

In his paper A Revision of Syngonium (Araceae) Dr. Croat expands on the observation geographical location can make a difference in the appearance of the leaves when he wrote, "Evidence that there may have been a long separation of populations of Mexican and Costa Rican or Panamanian species can be seen in the morphological variation among Mexican and Costa Rican populations of the two most widespread species in Central America. Both S. podophyllum and S. acrophyllum populations in Costa Rica and Panama differ in many ways from those in Mexico."  By simply existing a few hundred miles apart in nature a species can be variable.

Variation due to the geographic location of a specimen as well as environmental and genetic factors is known as phenotipic plasticity or the ability of an organism to change in response to changes in its environment.  The phenotipic plasticity of a plant can be the result of natural selection due to the parents of a specimen as well as differences in nutrition, disease and light intensity. 

Individual specimens of the commonly collected plant many collectors know as "Philodendron scandens" (correctly Philodendron hederaceum) that have been found in Central America can look very different from those collected in Brazil, Peru, or Colombia.  In fact, the plant's appearance can be altered simply by age.  Those changes are primarily known as the natural variation of the species but when the age of the plant is involved ontogeny also becomes a factor. 

Variation occurs over a very long period of time that can easily span thousands of years.  The effects of long term variation on a plant species is misunderstood and has created a great deal of controversy, particularly among collectors.  When a grower sees two plants of the same species with leaves that appear to be different in comparison to one another the collector almost always assumes the two are different species.  That assumption may not necessarily be accurate. 

Understanding the confusion

Confusing?  Perhaps we can help you understand the dilemma of natural variation versus the changes in the life spanning process known as ontogeny.  In the rain forest there may be many "faces" and shapes on a single plant species and that process can be either ontogeny or natural variation.  In previous eras botanists often granted different scientific names to a large number of plants that did not "appear" to be the same.  When it later came to the careful examination of each one of those "species" some were commonly found to possess the same scientific features, especially in the sexual characteristics found on the spadix.  This discrepancy compels a reversion to the first published name accepted by science for that species as long as the name was correct to the proper genus.

Plants are more like humans than you think

Natural variation with plants can easiy be equated to varied beautiful races found in our own species. There is only a single species of human being known as Homo sapiens and members of our species have many facial differences and body shapes, sometimes distinctive to our race or the part of the world in which our family originated.  We realize our species has different races which don't look exactly alike but we also understand there is only a single species of humans.  The only major difference in most humans is skin color, hair color, height, weight, facial feature such as color of the eyes.  All humans still have the same basic internal organs and same basic external body parts.

Even though there are many variations in skin color in our species we would never consider declaring an individual a different "species" simply because of the color of their skin.  What about the color of the hair or eyes?  if we were to declare each individual with a different skin, hair or eye color a different "species" the confusion would be unfathomable.  Which race, hair color or eye color would be the base species?  If some extreme "scientist" were to claim the Anglo, Negroid or the Asian race was the accepted species and all others needed a new name for their "species" the world would surely "implode" and rational scientists would immediately declare those new names invalid. 

Often we admire racially mixed individuals since they have captured some of the best qualities of each of their parents.  The same can easily be true of variations within a single plant species.  If one plant variation has developed a unique "skin" color as is common with some human races and another has very unique eye qualities the combination of the two can produce outstandingly attractive offspring.  If one parent had unusually long lobes or an unusually shaped leaf blade and that is combined with another parent of the same species that has other unique characteristics, the plant offspring can be stunning and is immediately thought by the untrained to be a "new" species.  Still, both parents are from the same genus and species whether plant or human.  Still, when we collect plants we often want to do the same thing as that "extreme scientist" simply because a leaf has a reddish underside while a plant that looks basically the same has a greenish underside.  Color has very little to do to do with the determination of a species.  Simply because the underside of one leaf is burgundy while another is green does not mean the two plants are different species.  They just had unique parents.

The "faces" of plants

Natural variation occurs in all plant species.  To the right are photos showing variations of Colocasia esculenta which is one of the most variable aroids on our planet.  This species has been cultivated as a food source for over 10,000 years and there many variable forms.  Colocasia esculenta has hundreds of "faces" which makes a single species appear to be very different plants. 

Still, all are the one species, Colocasia esculenta.  You can read about that species here:  Colocasia esculenta 

Both ontogeny and variation are common in juvenile plants.  Collectors rarely understand the young plant specimens they grow will not remain in the juvenile form for the plant's entire life, especially if allowed to climb.  Without their ability to gain height most species would never be able to exhibit either morphogenesis or natural variation.

Most collectors never experience these changes because we grow our plants in a controlled environment in less than ideal conditions that offers no way to climb.  In nature many never have their roots in soil but we almost always plant them in dirt.  In the forest many climb and are watered almost daily while we often water them once a week.  While these plants desire and need bright light, we often grow them in a dim bathroom.  Even though they want to climb we force them to spread across a living room table.  Plants need to climb but on a table or kitchen counter they simply remain in their "baby" form.  As a result, it is important we understand why plants climb.

The "needs" of plants and what drives them in the first stages of growth

Many houseplants live in a rain forest where they are epiphytes.  An epiphyte is a plant that grows with its roots attached to a tree and by definition never has a root in soil.  In the forest they have high humidity and  roots that are almost always damp as a result of the humidity and rain.   House plants rarely receive the conditions Mother Nature intended for them to find in nature so their natural growth is inhibited. 

In the rain forest young specimens perpetually seek the shade of a tree through a process known as scototropism.  Scototropic growth is a part of the natural coding of the DNA of many tropical plants and causes them to seek darkness in order to find a tree to climb.  The plants need to climb since the light at ground level is low and the specimen needs brighter light for the production of chlorophyll. 

Why do the leaves go through morphology and change as they seek a tree to climb? Their own DNA points them towards a tree so they can begin their climb toward the light and to adulthood. 

Once it eventually begins to climb a plant does so in order to find brighter light since the brighter light allows the plant to produce more chlorophyll.  Chlorophyll is the green pigment in every plant that captures sunlight to produce photosynthesis.  Plants draw in carbon dioxide and though a process known as being autotrophic they  combine it with water that enters the cells of the leaf as a result of rainfall.  Autotrophs create their own food by utilizing photosynthesis. 

The process is completed through the reduction of carbon dioxide by adding the hydrogen component of water (H2O) to create organic compounds.   In biology the term reduction indicates the hydrogen is stripped away from the oxygen.  In green plants an autotroph converts physical energy from sun light into carbohydrates in the form of sugars. They may also form chemical energy by synthesizing complex organic compounds from simple inorganic materials in order to produce fats and proteins from light.

The products of photosynthesis produced in the leaf are both sugar and oxygen and the oxygen is given back to the environment while the carbohydrates are used to feed the plant's own growth.  Although home growers rarely understand the need for brighter light and high humidity to grow their plants, stronger light and misting are essential to healthy growth.  The next time anyone tells you misting is not important since the water evaporates too quickly, recommend they read up on "autotrophic" growth and photosynthesis.  It should also be understood plants also need oxygen and draw it in through their roots.

Web forum sites sometimes have lengthy "discussions" over which juvenile Philodendron or Monstera  is a particular species because the grower does not understand ontogeny or heteroblastic change in aroids.  Aroids commonly are heterophyllus which is a process causing the plant to possess very different appearing leaves on the same vine (see examples of Philodendron atabapoense (below) and Philodendron bipennifolium below, left),  Please note the underside of the juvenile blades are burgundy but as the blade ages the coloration fades to a light green.

 

The morphogenesis of an aroid is similar to the changes observed in a human baby as it grows from a new born to an infant progressing on to a toddler, a preschooler, an elementary student and finally into the elder years of life.  It is rare for an older adult to meet a childhood acquaintance and immediately recognize them as an old friend due to the significant ontogenic changes in the human body.  The same progressive changes in the form of a leaf can make determining a species by only seeing a juvenile extremely difficult.  Those changes in the form of a plant are also known as heteroblastic development which is the successive way leaves progressively change in both shape and size as they mature. 

Heteroblasty can be so drastic the juvenile, intermediate and adult look so different they cannot be recognized by a grower without some degree of scientific training.  Species such as Monstera adansonii have many variations and as a result have numerous synonym names.  The juvenile form is almost always sold on eBay as Monstera friedrichsthalii which is simply a synonym.
The juvenile form of some Monstera species such as Monstera dubia begin their growth appressed (photo, right).  Appressed indicates the plant is pressed tightly against the host in a form of heteroblasty known as shingling.  In the shingle growth form species produce very short petioles causing their blades to be held flat against the host tree or rock.  The petiole is a part of the leaf and is the stalk that supports each individual leaf.  Although collectors often call the petiole a "stem", the stem is the central axis and main support of the plant, not a part of any leaf.

As a juvenile Monstera begins to climb the leaves sometimes overlap and the stacked blade sequence appears similar to the shingles or tiles on a roof, thus the name "shingle plants".  However, as Monstera dubia continues to grow the leaves begin to produce longer petioles that start to stand away from the tree.  As they grow longer and the blades mature they have no resemblance to the juvenile leaf form (photo right, above).

"Extreme forms" and "collector bias"

Before any further explanation on variation, consider this quote from aroid expert Leland Miyano.  Leland spent a great deal of time working and studying with legendary artist/plant collector Roberto Burle-Marx in Brazil.  His extensive field work in South America makes him one of the most qualified people in the aroid community.  Pay close attention to his explanation of "extreme forms" and "collector bias".  Leland explains, "I think it is best to explain variation within a species as it relates to populations, distribution and genetic exchange. If you have two widely separated populations of the same species that have not been exchanging genes for a very long time, the two populations may look very different from each other.  Sometimes the distance itself may not be great if there is a physical or other barrier to cross pollination. 

If one of the populations have an extreme form, then this trait may impact the characteristics of that population.  Normally, if there are intergrades or intermediates of forms from one extreme to another, only one species is involved.   With regard to collectors, there is collection bias in the field.  By that I mean the variations that are most attractive or different are often selected from populations for introduction into cultivation.  The other bias in this regard happens due to ease of collecting area.  For example, when a new logging road is cut and only the plants easily collected near the road are obtained.  These selections may or may not be characteristic of the species as a whole and may in fact be extreme forms."

Leland clearly explains why those individuals that make wild collections select the best looking plant forms they find in the forest.  In other words, they take the plants they believe are "beautiful"! 

Collectors taking plants from the forest rarely select the common natural specimens but instead those "extreme forms" that are more attractive.  Therefore, what we often find available to a collector is not necessarily representative of the natural plants found in the environment. 

That is the very basis for a plant collector not understanding natural variation as it relates to our inability to believe two plants with a very different or "extreme" appearance are the same species!  We often only see the "beautiful" forms, not those that are common in nature.
 

Why a photo can be deceptive

Have you ever wondered when you do a "photo search" on Google why you come up with very different appearing photos for the same species?  Sometimes that happens because the person who posted the image is inexperienced and has posted a bad ID for the plant.  There are no "internet police" to verify all the photos on the net are accurately described!  Many times, especially if the website is scientifically verified, those photos of a single species will be dramatically different due to either heteroblasty or natural variation within a species!  Let's consider the case of Philodendron pedatum shown to the right below.

At one time there was an unanswered question on a garden website asking for the correct scientific name for an unknown juvenile Philodendron.  People were guessing a hybrid known as "Florida Beauty" as well as several other speculative names but none of the suggestions were accurate.

Even though this website has this species listed including photos of several natural variations, and because the plant on the garden forum did not "look" exactly like any photo on this or another website, that led the grower to apparently refuse to understand his species was variable.  No explanation as to natural variation offered was satisfactory.  If a grower will not accept the science of natural variation no effort to verify a scientific name can ever be achieved. 

Finally  one individual offered the correct ID but the grower still refused to accept the identification because his plant didn't look like any photo on the internet!  He had totally missed any explanation of natural variation.

Although I was relatively sure I knew the correct species I finally asked three of the best experts including Dr. Croat to confirm the correct identity which was Philodendron pedatum. The photo in the upper left hand corner is a juvenile specimen of P. pedatum but the two photos by naturalist Joep Moonen (yupe) at the right as well as my photo from the Missouri Botanical garden are all variable adult forms.  Joep's photos were taken in the rain forests of French Guiana.  

This species commonly takes on a variable blade appearance in different rain forests due to variation in the same species. The adult forms look little like the juvenile form as a result of heteroblastic growth. 

The differences in the juvenile and the multiple "facial changes" the plant undergoes before reaching adulthood and finally "old age" is known as the heteroblastic change while the total difference in appearance of the adult specimens is also natural variation.  Since the photo on the garden site was neither a juvenile nor an adult and was not a perfect match to a known photograph all but one contributor found it difficult to accept the correct scientific name.  A single photograph can rarely be trusted to establish a correct identification.  

When you are seeking a good ID be certain you photograph the plant from many angles including both the upper and lower leaf surface, the petiole (leaf stalk), the stem (central axis of the plant) and any other feature that can be observed.   Once you complete this article try an experiment by doing a photo search on Google for "Philodendron pedatum".  Unless you place the name in quotes many of the photos will be a plant other than P. pedatum and even then, some will be incorrectly identified. 
 

Synonymy and why some collectors refuse to "believe"

I have received mail from individuals who attempt to tell me the concept of natural variation is not possible and they know for certain the scientific plant names they are using is both scientific and correct.  Some collectors don't understand the name they use was at one time considered correct but is no longer an accepted name because it is only a duplicate name for a known species.  Very few plants species don't have at least one synonym.

In the case of Philodendron pedatum many collectors are using a "synonym" of the accepted name.  Philodendron pedatum has five synonym names including Philodendron quericifolium, Philodendron laciniatum, Philodendron amazonicum, Philodendron laciniosum, and Philodendron polypodioides, however the only correctly accepted name is Philodendron pedatum.  Some plants have 20 or more known synonyms because their variations do not look alike. 

The "extreme form" case of Philodendron hederaceum, aka: "scandens, oxycardium, and micans"

Philodendron hederaceum undergoes heteroblastic change as it grows and has many variations.  As a result, the species is the source of confusion within the world of collectors.  When examining a juvenile plant collectors frequently prefer to call Philodendron hederaceum by names such as Philodendron scandens, Philodendron micans, Philodendron miduhoi or one of many other names given this species in the 1800's!  Those names are not different species but instead only non-accepted synonymous with the species P. hederaceum! 

Some collectors just won't accept the fact all these plants are the same species and continue to apply their own ideas as to which is P. scandens or P. micans or even a cultivar known as Philodendron 'Brasil' (sometimes published as Philodendron 'Brazil') while refusing to recognize he plant by its only accepted scientific name Philodendron hederaceum as if the name was a disease. 

It is at least possible the reason collectors see so many different names for Philodendron hederaceum available for sale by growers is a matter of commerce.  Aroid collector Ted Held is a collector of the aquatic aroids in the genus Cryptocorne and wrote in a private message, "the persistence of certain nomenclature misnomers might, just might, be an aspect of commercial sleight-of-hand. For example, how much more will a separate species identity be worth compared with simply being a cultivar of a common species?  I’ll bet a separate species name will command a higher price. If I import a Cryptocorne from Asia, I know that a common C. wendtii variety will be cheap whereas if it’s called some other name, perhaps of some rare species that is never in commerce, the exact same clone will fetch a premium price, and who will be the wiser? I suggest that part of the persistence of misnomers is because they are cash cows for certain growers."  It is likely some sellers prefer to sell you all the natural variations of Philodendron hederaceum using different names in order to bring in additional sales.

Collectors tend to believe if it has velutinous (or velvet) leaves with a distinct heart shaped blade it must be Philodendron micans and if the underside of the leaf is green it must be Philodendron miduhoi.  Do you know in a rain forest that plant can grow to 48cm  or 19 inches?  See photo right below.  Do you know these variations can lose that velvet sheen?  Do you know these variations will eventually lose the burgundy color on the back of the leaf?  Do you know the shape of the leaf blade can totally change?  That is the world of natural variation and the morphogenesis within a species!

More importantly, do you realize leaf size means nothing when attempting to determine the correct species?  One of the first lessons Dr. Croat ever taught this collector was size and blade color are rarely important to determining a species!  If you are tall and a friend is short and a different race that does not mean you are not both humans in the species Homo sapiens.

A plant species is determined by examining the stem, the nodes, the internodes, the roots, the cataphyll, the petiole, both surfaces of the leaf blade for specific characteristics of the primary, interprimary and minor leaf veins but the ultimate determination is made by examining the sexual characteristics of the inflorescence.  Without an inflorescence it is all but impossible to make a 100% certain determination as to species. 

Most collectors have only juvenile plants and have never observed an inflorescence (spathe and spadix) since it forms 20 meters (60 feet) above the ground in a rain forest..  As a result they have little scientific information to attempt an accurate identification.  

In nature the species does not particularly enjoy low light which is the exact way collectors always want to grow it!  Instead it climbs any tree trying to reach the sun so it can morph into an adult plant (photo, left)!

Aroid botanist Dr. Thomas B. Croat of the Missouri Botanical Garden in St. Louis, MO. once explained if you were to make collections of Philodendron hederaceum throughout its very large natural range including Mexico, all of Central America, all of tropical South America and some of the Caribbean you would find countless slight natural variations within the species and all those hundreds, possibly thousands of variations, have never been granted their own exclusive name.  As Dr. Croat explained, these natural changes are simply the nature of plant evolution.  Still, the synonym names that have stuck are extremely well entrenched in the minds of plant collectors. 

A settled argument

The discussion among botanical scientists about the natural variation of Philodendron hederaceum goes back close to 180 years and is now a closed issue.  Since the mid 1800's botanist once argued about the synonyms of Philodendron hederaceum.  Botanist Heinrich Wilhelm Schott (1794 to 1865) transferred Arum hederaceum to the genus Philodendron in1829 when he realized it was not an Arum.  In 1856 he also transferred Philodendron scandens, Philodendron oxycardium, Philodendron micans and others as synonyms of the species.  In 1899 botanist Gustav Heinrich Adolf Engler (1844 to 1930) reversed Schott and once again treated Philodendron hederaceum as four distinct species and declared Philodendron scandens, P. oxycardium, P. micans and a name were separate species.  Despite the confusion, botanist Julian Alfred Steyermark (1909 to 1988) again reversed Engler and in 1958 cited the "species" were only synonyms of Philodendron hederaceum since their characteristics were the same.  Other noted botanists have written opinions all along the way about the variation within the species Philodendron hederaceum and it is now considered a settled argument with P. hederaceum being the accepted species name and all others as synonyms. 

Within the rules of botany it is well established that the very first name ever granted to a species becomes the accepted name.  As a result, all the commonly used names for Philodendron hederaceum known by collectors are now synonyms of the accepted species and are no longer used within science.  

The confusion continues via the internet

The scientific information in this text was taken from the published work of aroid botanist Dr. Tom Croat along with numerous email exchanges and visits to his office.  Additional information came from the text The Genera of Araceae by Dr. Simon Mayo, Josef Bogner and Peter Boyce.  Some material was contributed by aroid experts Julius Boos and Leland Miyano.   Some of the photos were contributed by grower Brian Williams, Dr. Ron Kaufmann, naturalist Joep Moonen, Dr. Josef Bogner, Phil Nelson of the Marie Selby Botanical Garden and grower Windy Aubrey.  All photos not otherwise credited were created by the author.

Text compiled by Steve Lucas, www.ExoticRainforest.com 

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