Monstera spruceana Engl.
Synonym: Monstera steyermarkii G.S. Bunting,
Basionym: Tornelia spruceana Schott
 

 

Published to science in 1878 by German botanist Heinrich Gustav Adolf Engler (1844–1930), Monstera spruceana has a wide distribution.  The species is native to Bolivia, northern Brazil, Colombia, Costa Rica, French Guyana, Guiana, Panama, Peru, Suriname and Venezuela. 

Named in honor of English botanist Richard Spruce (1817-1873), M. spruceana is one of the few members of Monstera section Marcgraviopsis.  According to some authors there may be two distinct species involved since the natural variation of the species is diverse.  Monstera spruceana has been observed growing at elevations ranging from 70 to 1400 meters (230 to 4600 feet) above sea level.

The species was originally published in 1859 as Tornelia spruceana but science later determined the plant was published in the wrong genus and as a result the name T. spruceana is now a basionym.  All species formerly in the genus Tornelia were transferred to the genus Monstera in 1866.  A basionym is the first valid published name applied to a taxon which has been proven by later researchers to be an invalid name.   Tornelia is now considered one of the four sections of the genus Monstera along with section Marcgraviopsis, section Echinospadix and section Monstera.

Monstera species as well as all aroids are variable.  Variability indicates the leaves and some other features of a species do not always appear the same.  Natural variability in aroids is the source of confusion among collectors that leads to a great deal of bad information, especially on the internet.  Just because the leaves of a plant do not always appear the same does not necessarily indicate a different species is involved.  The final determination must be made by comparing many features including the arrangement of the venation (vein structure), the specific characteristics of the petiole, the cataphyll, the stem, root system and the inflorescence. 

Once you complete this article you may wish to read this link for additional information on variation within aroid species.

All major botanical gardens house a collection of dried herbarium specimens in order to compare new material to a verified known specimen.  A herbarium sheet is considered the most positive method of determining if a plant is a particular known species since the dried features are more prominent than on a living specimen.  Dried specimens of Monstera spruceana have been confused by researchers with Monstera dilacerata and Monstera subpinnata which are found in section Monstera.  In the adult stage a dried specimen can be confused due to the similarity of some features but the differences are easily avoided as long as the herbarium sheet contains the dried leaf lamina along with the spadix and peduncle of the inflorescence.

In addition to natural variability aroids undergo morphogenesis as they grow.  The morphogenic changes are known as a plant's ontogeny while the changes in their shape is called  heteroblasty.  Ontogeny is the natural and progressive changes made in any living organism as it grows.  Collectors rarely understand the young plants they grow will not remain in that form for its entire life, especially if allowed to climb.  Web forums sometimes have lengthy "discussions" over which juvenile Monstera is a particular species because the grower does not understand how the ontogeny of an aroid causes change.  As a result some believe the juvenile form of Monstera spruceana may be another species or genus such as a Philodendron or a form of Monstera dubia.  As you can see from the photos on this page these species look very little alike in the juvenile stage.

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 to a toddler, a preschooler, an elementary age student and into the teenage years.  As the child grows it morphs into a young adult before progressing into full adult maturity and she/he finally assumes the body common to the elderly stages of life.  As a human matures it changes and so do aroids.  It is rare for an older adult to meet a childhood acquaintance and immediately recognize them as an old friend  thus it is equally difficult to recognize the juvnile form of most aroids.

Those progressive changes in the form and size of a plant are known as heteroblastic development, or the successive way leaves progressively change in both shape and size.  Trying to identify an aroid by examining only a juvenile specimen is often impossible since we have no method of knowing the precise form it may take at any particular stage of its growth.

The juvenile form of Monstera spruceana begins its growth appressed.  Appressed indicates the plant is pressed against the host.   This form of heteroblasty is known as shingling.  In the shingling growth form certain species of Monstera as well as other genera produce very short petioles causing their blades to be held flat against the host tree.  As the plant climbs the over lapping blade sequence has an appearance similar to the shingles or tiles on a roof.  Thus the name "shingle plants". 

Monstera spruceana has been observed growing a meter (3 feet) or more in the shingle form before beginning to change to the pre-adult form.  However, in some specimens the shingle stage does not grow much past the first few dozen leaves before beginning to change.  Both the juvenile shingle stage as well as the first changes into the adult form can be seen in the photos on this page.  In the field notes of aroid botanist Dr. Thomas B. Croat Ph.D., P.A. Schulze Curator of Botany of the Missouri Botanical Garden in St. Louis, MO.  he notes having observed variability in the juvenile blades.  The young blades may be either somewhat velvety and dark green or gray to plain green as well as matte with dark green veins.  The plain green  form is matte to semi-glossy on the underside while the dark green form is somewhat velvety as well as glistening on the upper surface.  Juvenile plants may also have a darker band along margin (edge) of major veins

The species may grow as either an epiphyte or a hemiepiphyte.  An epiphyte is a plant that does not have roots in the soil, but instead lives above the ground's surface supported by another plant, normally a tree. Epiphytes gather nutrients and water from the air or from organic debris from dead vegetation or from the droppings of rain forest animals. 

Hemiepiphytes are divided into two forms with primary hemiepiphytes beginning as seeds in the droppings of a rain forest inhabitant that has eaten the berries of an aroid that germinate on the trunk or limbs of a tree in the same way an epiphyte forms.  The primary hemiepiphyte then develops long roots that eventually reach the ground. In this way a hemiepiphyte attains height in the forest as quickly as possible to reach brighter light.

Secondary hemiepiphytes start their lives in the soil or on a tree trunk near the ground with grounded roots to gather additional nutrients but then then climbs the host where it morphs into the adult form, sometimes completely loosing the connection to the ground.  

As the blades begin to morph they are oblong-ovate finally becoming divided into lobes.  Upon occasion the host tree will fall as a result of fire or a storm requiring a specimen to become terrestrial until it can find a new host tree to climb.  You can observe this precise event in some of Joep Moonen's photos of the species growing in French Guiana.

The adult leaf blades of Monstera spruceana are bicolorous as well as subcoriaceous (less than leathery) to moderately coriaceous (leathery) with a weak glossiness to the blade's upper side (known as the adaxial surface).  Bicolorous means two colored;, i.e. medium green with a dark green as the base on the adaxial side.  Fully grown blades may be a dull matte or weakly to semi-glossy but are slightly paler in color as well as  weakly glossy on the abaxial surface (underside). 

The major feature of an adult leaf of this species includes a pinnatifid leaf with broad pinnae.  Pinnae means "feather" in Latin and describes a leaf that possesses leaflets arranged more or less in the form of a feather.  Pinnatifid indicates a single leaf with divisions reaching almost to the midrib.  Adult leaves typically measure 50 to 70 cm long by 25 to 40 cm wide but the size is also variable. 

The midrib of the leaf is either flattened, slightly sunken or sulcate above but narrowly raised and slightly paler in color on the underside.  Sulcate indicates a furrow or groove such as the depression sometimes observed on the upper surface of a petiole commonly known as a C-shaped depression. 

The midrib is the thick central vein which separates the two halves of the leaf while it mechanically supports the blade as well as being the means for the transportation of nutrients and water.  The primary lateral leaf veins are convex and sometimes whitish below with the minor veins slightly obscure.   The primaries are the veins that branch off the midrib and extend to the leaf margin (edges).   There should be two to four primary lateral veins per pinna with four to ten pinnae per side.  It is not uncommon for some leaves to be pinnatifid on only one side. 

The stem of all plants is the base, central axis and main support which is normally divided into nodes and internodes. The nodes are separated by the internodes that can produce a complete leaf or roots from nodes that hold buds. The stem's roots then anchor the plant either to the ground, a tree. 

Although many collectors believe the stalk that supports the leaf is the "stem", the support for a leaf blade is known as the petiole.  The petiole and leaf together are the complete leaf.  The petioles of Monstera spruceana are typically one-third to two-thirds the length of the of the leaf lamina,  The petioles are normally a medium green while being weakly glossy and often speckled.  The petiole possesses a deciduous petiolar sheath that is curled inward.  Petiole sheaths are extensions on each side of the petiole that are similar to "wings" that may envelope the successive newly developing leaf blade.  The term deciduous indicates the sheaths eventually fall from the plant.

A slight to deeply sulcate geniculum can be observed at the tip (apex) of the petiole. A geniculum is a wrist-like organ always located at the apex of the petiole that allows a leaf to rotate and orient itself in order to control to some degree the sunlight it collects.

Even though collectors commonly believe a Monstera is a form of Philodendron, the genera Monstera and Philodendron  are not one and the same. There are several differences in Monstera species that include the growth of holes known to science as fenestrations and the presence of a geniculum which is commonly associated with plants in the genus Anthurium.  Monstera also have differences in the sexual reproductive process.

During sexual reproduction the inflorescence of Monstera spruceana produces a spathe that is white surrounding a spadix.   The inflorescence of Monstera species are bisexual and produce perfect flowers that include both sexes within a single flower while Philodendron species produce unisexual flowers that have both male and female flowers that grow separately.  Both bisexual and unisexual aroids produce blooms consisting of a simple leaf-like spathe attached to the

The inflorescence of Monstera spruceana is supported on a peduncle that is terete (round) and shorter than the spadix,   The inflorescence is solitary and if pollinated the spadix begins to produce berries and then becomes known as an  infructescence.  A spadix which is producing fruit is white.  

To learn more about natural pollination within aroid species refer to this link.

The scientific information in this article was extracted from the field notes and published material of Dr. Tom Croat along with information available on CATE Araceae   My thanks to both Dr. Croat and to my friend Joep Moonen for the use of their photographs.
 

  
 

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