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The Exotic Rainforest
Plants in the Exotic Rainforest Collection
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Philodendron renauxii Reitz

Philodendorn renauxii, Photo Copyright 2009, Steve Lucas,
Philodendron renauxii Reitz
Paddle Leaf Philodendron

My thanks to Anna Haigh of the Royal Botanic Garden Kew for providing portions of the scientific data for Philodendron renauxii Reitz.  Portions of the botanical information used on this page was extracted from the field notes of aroid botanist Dr. Thomas B. Croat Ph.D., P.A. Schulze Curator of Botany at the Missouri Botanical Garden in St. Louis, MO,  

Philodendron renauxii Reitz, Paddle leaf Philodendron, Photo Copyright 2007, Steve Lucas, www.ExoticRainforest.comPhilodendron renauxii (ren-WAW-e-eye) is found exclusively (endemically) in the southern coastal Brazilian state of Santa Catarina (SE-ta  ka-ta-Rin-na) south of São Paulo.  There is also the village of Santa Catarina in the northeastern portion of Brazil but these are different locations many kilometers (miles) apart.  The state of Santa Catarina has one of the highest standards of living in Brazil. 

Uncommon in North American aroid collections little has been published regarding this species since it was first published in the Brazilian scientific publication Sellowia in 1957.  Philodendron renauxii is found at an elevation of approximately 350 meters (roughly 1000 feet) above sea level in the forest region between São Paulo, which is the capital city of the state of São Paulo, and Florianópolis (nicknamed Floripa)  which is the capital city of the state of Santa Catarina  Florianópolis is located mostly on Santa Catarina Island.
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According to personal communication with aroid botanist Marcus A. Nadruz Coelho, Diretoria de Pesquisas, Instituto de Pesquisas Jardim Botanico do Rio de Janeiro (Rio de Janeiro Botanical Garden) in Brazil,  "The specimen that you have has the characteristics of P. renauxii. The species, so far, is endemic to Santa Catarina (southern Brazil), but I think it can be found in the state of Paraná located between Santa Catarina and São Paulo. I believe the distribution of the species is still poorly known due to lack of collection.  It is a species typical of wet and cold places and here in Brazil the flowers appear from October which is standard for the genus Philodendron. It is widely used in landscaping because it is very beautiful."  In a follow up message Marcus continued, "There are few records of the species in Brazil so the actual variation in the size of the leaf is unknown. With the existing collections the size of the leaf is up to 40 cm in length."  A blade length of 40 cm would equal approximately 16 inches which is roughly the size of the  blades found on our specimen.  Despite the fact that Marcus prefers not to be called "Dr. Nadruz", he holds a PhD in aroid botany from the Universidade de São Paulo and has always been extremely helpful in providing valid scientific information on Brazilian aroid species.

One of Brazil's unique Philodendron species, Philodendron renauxii is a terrestrial Philodendron renauxii midrib, Photo Copyright 2009, Steve Lucas, www.ExoticRainforest.comspecies which crawls cross the ground rather than climbing in most cases.   Rather than having the cordate leaves (heart shaped) common to many Philodendron species, Philodendron renauxii has leaf blades that are only partially cordate and instead are bluntly lance shaped while being both elongated and concave with a shape like that of a curved paddle.  The sub-coriaceous (thin leather-like) leaf blades of Philodendron renauxii can stand 60 to 120cm in height (2 to 4 feet) above the ground.  In addition the leaves are dark green and are semi-glossy on the adaxial (upper) blade surface.  The blade coloration is somewhat paler on the abaxial (lower) blade surface as well as matte.  One very popular horticultural reference indicates the leaves are "sickle-shaped" but that description would imply a scythe shape  such as found on the old-world agricultural tool.  That tool which is used for cutting grain is both thin and curved and does not fit the description of the species Philodendron renauxii. 

The midrib which is found at the center of each leaf blade (photo, left) is broadly convex-flattened (only slightly raised) and slightly paler in color on the underside.  The primary lateral leaf veins are weakly raised and are often obscure on the upper surface while also barely visible on the underside.  The minor leaf veins are both fine and only slightly visible on the upper blade surface but are more distinct on the abaxial surface (underside)

Philodendron renauxii Reitz, stem and petioles,  Photo Copyright 2009, Steve Lucas, www.ExoticRainforest.comThe petioles which are scientifically the stalks to which the lamina of the leaf blades are attached are both obtusely and shallowly sulcate.  Obtuse simply means "bluntly" while in  botany sulcate may indicate either a single channel or canal running down the axis of the petiole.  In some species sulcate can indicate a series of tiny parallel groves running down the axis.  In the case of Philodendron renauxii the petiole is canaliculate and you can easily observe a shallow canal running down the upper surface.  The purpose of the canal is to direct rain water which has fallen  on the blades toward the stem and roots. 

Despite common misconceptions the petiole is not the stem as is often claimed by plant collectors.  The petioles are strictly the stalks which connect the leaf blades to the stem at the base of the plant.  The petioles grow from nodes found along the stem's length.  (see photos right and below left)

The stem of any Philodendron is the base of the plant (see photo left) and in the case of Philodendron renauxii typically Philodendron renauxii Reitz, stem and petioles,  Photo Copyright 2009, Steve Lucas, www.ExoticRainforest.comruns across the ground.  The stem has nodes at regular intervals and the petioles as well as the roots grow from those nodes along the stem's length.  The stem segments which separate the nodes are known as internodes. 

When a new petiole grows from a node it is surrounded by a cataphyll (photo, right) which is a bract-like modified leaf that surrounds and protects the new leaf as it develops.  A cataphyll is any foliar organPhilodendron renauxii Reitz cataphyll, Photo Copyright 2009, Steve Lucas, that has no differentiation between the petiole and the blade.  The cataphylls of Philodendron renauxii are medium green while weakly glossy and persist briefly (remain) after the blade opens until they become deciduous and drop from the plant.  The cataphyll is the singular most important identifying characteristic of an aroid.

All Philodendron species are members of the larger plant family known as Araceae, commonly called aroids.  An aroid is a plant that reproduces via the production of an inflorescence which in aroids is known to science as a spathe and spadix.  The inflorescence is supported by a stalk known as the peduncle which is the internode between the spathe and the last foliage leaf.    The spathe is shaped like and a appears to be a hood which opens during the reproductive cycle known to a botanist as anthesis. Most people think the spathe is a "flower" which it is not.  The spathe is a modified leaf and at the center of the spathe is the spadix where berries containing seeds will develop provided the female flowers are pollinated.   If you explore the spadix with a magnifying glass when it is at sexual anthesis and is ready to be pollinated there are very tiny flowers which are cleverly divided by nature in the genus Philodendron to prevent self pollination.  Those species that are divided into zones of flowers with a single sex are known in botany as being "unisexual". 

Philodendron renauxii Reitz inflorescence, spathe, spadix floral chamber, peduncles, Photo Copyright 2009, Steve Lucas, www.ExoticRainforest.comThe tiny female flowers are hidden in their own zone found inside the floral chamber at the base of the inflorescence and as a result are often difficult to observe.  The sterile male flowers which produce the pheromone or "perfume" the plant uses to attract the assigned species of Cyclocephala beetle to pollinate the female flowers are found in their own zone just above the female flowers and nearer the top of the floral chamber.  At anthesis the temperature of the inflorescence rises dramatically as a result of a chemical reaction in order to propel the "perfume" through the rain forest.  The beetles can sense the pheromone from as far away as 200 meters (650 feet).  The Pollen on Philodendron renauxii, Photo Copyright 2009 Steve Lucas, www.ExoticRainforest.commale flower zone can be found all along the upper spadix and their purpose is the production of pollen (photo right). 

When the spathe first opens the female flowers are fertile for only a short period of time which is when the sterile male flowers begin the production of the scent (pheromone).  The female flowers complete their anthesis within less than 24 hours and are spent well before the male flowers begin pollen production.  The beetles sense the scent and are drawn to the heat since the inflorescence offers them both a source of food as well as warmth during the night.  The beetles stop at any plant producing the same pheromone for food and warmth as they fly through the forest.  As a result they  bring fresh pollen from another plant that is currently at male anthesis in order to pollinate the female flowers which are currently at sexual anthesis. 

There are two methods to determine if Philodendron renauxii is at female anthesis.  The first is the production of the pheromone which can be sensed by the human nose as well as by the beetle and the second is a "tanline" which becomes visible on the spathe.  My friend and aroid expert Leland Miyano explains,  "The tanline is formed by the separation of the overlapping edges of the spathe. As the edges begin to move apart and open you will see a tanline of sorts where the overlap was. This region, formerly protected from the sun, is lighter in color than the exposed parts of the spathe."

For a more detailed explanation of aroid pollination click this link

Philodendron renauxiireflexed spathe limb, Photo Copyright 2009, Steve Lucas, www.ExoticRainforest.comBased on personal observation the spathes of Philodendron renauxii emerge green but as they open lighten in color with a greenish white interior.  Once fully open there is deep within the throat of the spathe a beautiful rose coloration.  During female anthesis the spathe does not necessarily open completely but the hungry pollinating beetles are able to force their way through the constriction into the floral chamber in order to eat the sterile male flowers which are rich in lipids which contain proteins.  By forcing their way into the floral chamber they then bring along pollen collected from another specimen and pollinate the female flowers inside Philodendron renauxii inflorescence (throat), photo Copyright 2009, Steve Lucas, www.ExoticRainforest.comthe chamber.  Once female anthesis is complete the limb or blade of the spathe at the upper edge of the spathe reflexes and turns back.  (see photo, right). 

Expert collector/grower Leland Miyano who lives in Hawaii has had extensive experience collecting exotic aroid species in Brazil and studied under master aroid collector Roberto Burle-Marx.  Roberto's extensive collection is now preserved and studied by the government of Brazil.  Leland has collected and grows this species and made these observations, "I have several very similar plants in the Philodendron renauxii complex.  All have paddle-shaped lamina.  The ones that match the isotype do not have back lobes.  I have plants with backlobes that do not want to climb and are always terrestrial and a few that will climb if given the opportunity.  Exactly what to call them, I do not know...they were all wild collections from SE Brazil."  As a result, it appears this species has several variations.

Philodendron renauxii Reitz< Photo Copyrigh 2008, Steve Lucas, www.ExoticRainforest.comThis is Leland's description of the spathe in 2007, "My Philodendron renauxii are blooming now.  The immature spathes are green with scattered red dots.  At anthesis, the outside and inside is pure cream colored.  All stages are present now.  Introduced ants and earwigs are inside the inflorescences.  I pulled apart some of the spathes to see the female zone and it appears that fertilization is taking place.  This is a guess...but something is happening...I do not know what a fertilized female flower looks like...but swelling from the immature state is happening.  Copious amounts of gelatinous sap are present on the female zone of the spadix."

Philodendron species are known to be highly variable and not every leaf of every specimen will always appear the same.  This link explains in greater detail the science of natural variation and morphogenesis within plant species.  Click here.


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