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New: Understanding, pronouncing and using Botanical terminology, a Glossary

 Are you watching the Amorphophallus titanum inflorescence at the Houston Museum of Natural Science?
Lois is an aroid and this page explains what you are seeing.

Photo of Lois below


Pollination in Aroids
Anthurium, Philodendron, Alocasia,
Amorphophallus, Colocasia, Spathiphyllum, Monstera

and other aroid genera

Philodendron imperfect flowers, Anthurium perfect flowers, Photo copyright 2010 Steve Lucas,

By Julius Boos
with additional input by Steve Lucas
All photos by Steve Lucas unless otherwise noted

Please note:  you can click on the photos to be taken to the correct page for additional information.
Aroid expert Julius Boos at Fairchild Tropcial Botanic Garden, Photo Copyright Ted Knight
My dear friend Julius Boos who authored the basis of this text died on July 11, 2010 after a one year battle with pancreatic cancer.  He was 64 years old and will always be missed.  Photo by Ted Knight.
The inflorescence of any aroid whether an Anthurium, a Philodendron, Alocasia, Colocasia, Monstera, Caladium or other member of any genus in the larger plant family Araceae is composed of a spathe, which many people incorrectly believe is a "flower", and a spadix which is at the spathe's center.  The spathe is more like a "flower holder" since it is a modified leaf or bract .  The flowers of Araceae are very small and grow along the spadix.  Each tiny flower is supported on a very small stalk known as a pedicel but the flowers can rarely be seen with the naked eye.
Phildoendron sagittifolium inflorescences, Photo Copyright 2010 Steve Lucas, www.ExoticRainforest.comThe spathe appears in the shape of a hood while the spadix that holds the flowers is a spike on a thickened fleshy axis.  In botany a bract is a specialized leaf that is associated with the reproductive structure of the plant.  The spadix can only produce flowers at sexual anthesis.  True flowers contain near microscopic sexual parts including anthers, stamens, and stigmas.  Some aroids have tepals but others do not. 
The spathe itself contains no sexual characteristics but all the flowers can be observed with a good magnifying glass on the spadix.  If these tiny flowers are pollinated then fruit in the form of berries containing seeds will eventually be produced.
The inflorescence of any aroid species is unique and is a primary method  used by botanists to determine the species of the aroid.   Although some inflorescences are not particularly beautiful many are dramatic in their appearance.   Regardless of the aroid's structure the basic reproduction and pollination techniques are similar but the pollination of an aroids is dependent on which of two basic flower configurations may be involved.  Those configurations are based on the structure of the inflorescence.   This article explains in basic terms some of the details of an aroid's inflorescence as well as how pollination is accomplished in nature.
Aroids are divided into two basic configurations with some inflorescences such as Pistia straitotes (Water lettuce) being very small.  The first produces a bisexual inflorescence with perfect flowers containing both male and female Pistia stratiotes, Water lettuce, Photo Copyright 2010 Steve Lucas, www.ExoticRainforest.comorgans mixed together throughout the  length of the spadix.  To help prevent self pollination the female flowers are receptive prior to the production of pollen by the male flowers.  The second or unisexual group includes those species which produce an inflorescence with imperfect flowers which are either male or female in separated zones. 
The separated zones are in regions from bottom to top and include female, sterile male, and finally the male flowers which are located higher on the spadix.   An overview of what happens under natural conditions in the rain forest is necessary in order to be able to understand what we are trying to replicate artificially under green house conditions. 

In nature an inflorescence signals that it is about to open and begins to emit an odor known scientifically as a pheromone that is attractive to
selected insect pollinators.  The pheromone is often released in waves so the intensity will rise and fall depending on the sexual activity of the inflorescence.  When the flowers are fully receptive the pheromone (perfume) is often more intense but then wanes and rises as the chemical is released.  Recent viewers of Amorphophallus titanum (Lois) at the Houston Museum of Natural Science were often curious why the scent was not always fully intense.  As the event reaches the conclusion the pheromone level often drops dramatically.  A photo of Lois is below.
 Although the natural pollinators for Philodendron are primarily beetles that are members of the subfamily Dynastinae found in the family Scarabaeidae known as Cyclocephala or "scarab beetles" there are also insect pollinators for genera  that include Euglossine bees, frugivorous bats (fruit eating), flies, weevils and sometimes even small birds including hummingbirds.  These pollinators which appear to be "assigned" by nature to a specific species, especially the Cyclocephala beetles, can Frugivorous bat, Photo Copyright Dr. Merlin D Tuttle, Bat Conservation International, www.Batcon.orgdetect the pheromones at distances of approximately 200 meters or over 600 feet away.  The beetles fly a zig-zag pattern through the forest in an effort to follow the "perfume" to its source.   It is suspected there are approximately 900 species of Cyclocephala beetles but only about one half have been scientifically identified. 
Photo of Frugivorous bat (right), courtesy Dr. Merlin D. Tuttle, Bat Conservation International,
In addition to beetles from the genus Cyclocephala  members of the genus Erioscelis are also known to pollinate some aroids.   Within Araceae (aroids) the primary insect pollinators for Philodendron are the Scarab beetles found in the genus Cyclocephala. Some beetle species are not host specific and visit members of both Philodendron subgenus Philodendron as well as Philodendron subgenus Pteromischum while a few visit other aroid genera such as Dieffenbachia, Homalomena, Syngonium, Xanthosoma and some other plant families including palms.   Many pollinator species are host specific seeking out only the pheromone (scent) of one particular species' inflorescence.  Pollinators for Anthurium are largely flies (according to their smell), Eeuglossine bees and Curculionids (beetles and weevils from the family Curculionidae.   Hummingbirds have been observed pollinating Anthurium sanguineum. 
Colocasia esculenta "Black Magic" inflorescence including spathe, spadix, female floral chamber. Photo Copyright 2009 Steve Lucas, www.ExoticRainforest.comOne or several of these insect species have evolved to be the specific or "assigned" pollinator of any particular plant species. Once the bodies of those "assigned" pollinators come in contact with the resin (if present) on the spadix (see photo, top of page) they collect and hold the dehisced pollen grains from one inflorescence which is shedding pollen at male anthesis and transport it to another bloom at female anthesis in order to cause the pollen to adhere to the tiny sticky female flowers, As a result pollination is achieved. The term dehisced indicates pollen that has been shed.
That ingenious design is nature's plan and in principal works very well as long as man has not intervened to destructively counterbalance the natural regions where both the plant and the pollinator were naturally selected to exist in the environment.  However, if enough of the natural area of either is affected the outside interference may strongly disturb the natural breeding grounds of these important insects are limited or defeated in their attempt to achieve natural pollination. 

Since many birds, bats and small animals including monkeys rely on the berries of aroids as a food source during  the reproductive season the destruction of any rain forest region may adversely affect the life cycle of countless plant and animal species.  Some have now either gone completely extinct or are unusually rare as the result of nothing more than the destruction of the habitat of a specific natural insect pollinator.  It is also thought the natural pollinator of species such as Philodendron spiritus-sancti may have become extinct due to to forest devastation.  That southeastern Brazilian Philodendron species is now incredibly rare  with only six specimens known to exist in nature as a result of deforestation. 


The inflorescences of Bisexual Species

spathe and spadix of Anthurium schlectendalii, Photo Copyright 2005, Steve Lucas,

Both bisexual and unisexual aroid plant species produce blooms consisting of a simple leaf-like and sometimes attractively colored spathe that is attached to the base of its attending spadix.  The spadix is a spike or rod-like structure along the length of which are hundreds of minute but actual flowers.
Within the bisexual inflorescence each tiny section on the spadix observed with a good magnifying glass is an individual perfect flower consisting of a central female structure with a stigma at its center having several male flowers surrounding that stigma.   Within Anthurium species as well as other genera the flowers are contained withing a roughly "diamond-shaped" structure known as a a perigone.  The male organs are almost impossible to observe except during male anthesis when they are actually producing pollen.  The spathe itself is not a flower but instead is a modified leaf.  Examples of a few of the genera of Araceae (aroids) belonging to the bisexual group include Anthurium, Monstera, Dracontium, Stenospermation, Heteropsis, Rhodospatha, Spathiphyllum and others.
All Anthurium produce "perfect flowers" which bear both the male and female sexual organs. However the stigma or female parts are ready for pollination before the male pistals produce pollen. Since the different portions of the flower are not  productive at the same time Nature works to insure pollination from another plant at male anthesis while discouraging self-pollination.  Once the female flowers have completed anthesis the male flowers begin to produce pollen which is taken to another plant by the insect pollinator. 

Anthurium perfect flower, Photo Copyright 2007, Steve Lucas, www.ExoticRainforest.comTo prevent self-pollination in nature two events occur, one following the other.  The first is the initiation of female anthesis.  At this reproductive stage the female flower's stigmas are ready to be pollinated by the pollen from another more mature inflorescence located on a near-by plant.  That second inflorescence would necessarily already have reached male anthesis.  After the spathe is fully opened, a process that may take a considerable amount of time including days or even weeks, the stigmas can be observed to produce a tiny drop of liquid on their tips.  This liquid serves to hold the pollen grains in place once presented by an assigned pollinator.   This liquid is produced in both bisexual and unisexual reproduction.  However, within Anthurium species it is at times possible for self pollination to occur since some flowers begin the production of pollen before all the female flowers are spent.

An odor which is sometimes attractive and at others hardly noticeable to the human nose (but always attractive to the specific pollinator) is produced and released at this time through a process known as thermogenesis (thermo= heat, genesis= birth).  That pheromone is distributed by an increase in temperature within the spadix as a result of the release of salicylic acid and other natural occurring heating of the spadix.  Salicylic acid is the same chemical compound used in the production of aspirin.  After female anthesis (AN-th-sis) is complete, usually in a matter of days, the stigmas dry and turn brown.  
p to several weeks."
Tiny Anthurium flowers, each contained in a perigone, Photo Copyright 2010 Steve Lucas, www.ExoticRainforest.comShortly after this event occurs male anthesis initiates and pollen begins to be produced.   In some species the pollen is observed as a powdery dust that is visibly shed while in others it appears like a fuzzy material on the spadix.  Pollen is also produced in a similar fashion within unisexual aroid genera. 
Within bisexual genera pollen is produced in rings around the spadix over a long period of time. Some genera produce pollen in these rings from the spadice's top progressing slowly on towards the bottom. More commonly in genera such as Anthurium the pollen production starts at the bottom of the spadix and continues upward to the very tip. Most Anthurium species have been found to produce pollen from the bottom of the spadix moving slowly upwards to the tip and in others such as Anthurium regale it was observed this species produces pollen beginning at the top of the spadix moving slowly downwards. Acroscopic pollen production is from the bottom up while basioscopic is from the top downward. Aroid botanist Dr. Tom Croat of the Missouri Botanical Garden offers this additional explanation of either event, "Most Anthurium produce their pollen acroscopically (toward the apex) but rarely basioscopically as in those with thumb-shaped spadices. I think that Dracontium produces stamens basioscopically."   













The inflorescences of Unisexual Species

Inflorescence of Amorphophallus titanum, a group of flowers

The second group of aroids are those which produce unisexual inflorescences.   Philodendron, Alocasia, Colocasia, Caladium, Amorphophallus and Xanthosoma species are representatives of this group.  All produce inflorescences in Amorphophallus konjac inflorescence, www.ExoticRainforest.comwhich the spathe consists of two sections, both normally wrapped around the spadix with a constriction separating the two sections.  The upper portion of the spathe is called the limb or blade while the lower is a convolute tube or chamber.  On the spadix the imperfect male and female flowers occur in separate regions or zones.   Normally the zone of female flowers occurs at the very bottom of the spadix within the lowest portion of the spathe known as the spathe tube or floral chamber.  Above this female zone at the constriction is a zone of sterile male flowers.  These sterile flowers produce a pheromone (odor) which attracts insect pollinators in exactly the same fashion as bisexual species.  Normally, above these sterile flowers and within the upper spathes blade or limb, occurs the zone of fertile male flowers.   The female floral chamber of some species is well hidden and often constricted. 

The floral chamber of Alocasia species can be tightly constricted just beneath the spathe.  The spathe of these species is divided into a convoluted thicker lower region which hides the female flowers.  The spathe is observed to have a constriction with the female zone being roundish to globe shaped (globose to ovoid).  When ready to be pollinated the restriction loosens to provide the pollinating insects access to the flower pistils.  Once pollinated the zone remains on the peduncle and opens to become the fruit producing region.  Once fruit begins to develop the inflorescence is then known as an infructescence (see list of definitions at the bottom of this page).  Allocation are pollinated primarily by beetles and flies.
In some genera the uppermost section of the spadix also consists of a zone of sterile male flowers.  In this group, female anthesis occurs just at or even before the spathe begins to show signs of opening.  In Caladium species and perhaps Xanthosoma species it has been seen the peak period of female anthesis and receptivity actually occurs the day before signs of opening can be observed. 
Amorphophallus titanum is somewhat different since it does not have a well defined floral chamber on the day the spathe first opens.  Dr. Wilber Hetterscheid, the world authority on the genus explains, "A. titanum doesn't have a real floral chamber at first because it opens wide, without any constriction closing it off. The male flowers are thus fully exposed during the female phase of flowering (when stinking), only shortly after that phase, the spathe closes again and then a kind of floral chamber exists. It is close to that moment when the pollen is released and the male flowers are indeed below the constriction that develops and as such in the chamber."  Amorphophallus species are pollinated mostly by flies and beetles of a variety of species.
A titanum is also different in regard to the sterile flowers.  Since the pheromone is normally released through the sterile male flowers this is significant.  Again, Dr. Hetterscheid explains the differences, "Anthurium titanum has no sterile flowers. The appendix is in fact one giant collection of sterile male flowers and that is why the heat development is found in both the male zone and the appendix. I guess the chemicals also emanate from those zones although there are reports of scent developed from the inside of the spathe base. So in fact sterile male flowers, functional male flowers and appendix are all expressions of one ontogeny, with different functions."
The insects that serve as pollinators in these genera are likely attracted by subtle odors propelled by natural heat produced within the aroid that is produced by the as yet unopened blooms.  With their hairy bodies and legs covered with pollen from a previously visited bloom already at male anthesis these beetles actually force their bodies through the slightly relaxed spathe opening and down into the floral chamber containing the receptive female flowers.   Pollination in nature is done by a species of  beetle or fly assigned that task by nature.   The beetles only stay inside the inflorescence long enough to pollinate the spadix, eat some of the pollen, breed and gather more pollen.  The beetles use the warmth of the spathe as a place to stay warm during the night as well as source of food since they eat the pollen and some of the flowers as well as mate within the spathe due to increased metabolism as it begins to close.
The inflorescence continues to open during female anthesis for only one day then on the second day the female flowers are no longer receptive and the upper male flowers open while the spathe is fully open and produce large amounts of pollen to be picked up on the bodies and legs of the departing beetles. Within unisexual genera male anthesis is usually complete in 24 to 36 hours, sometimes less.  Male anthesis rarely lasts more than a single night.  This serves to assure the newly collected pollen is transported to a newly opening inflorescence while it is fresh and when the second inflorescence is first approaching female anthesis.  French aroid pollination researcher Marc Gibernau added this explanation, "one reason for the beetles to leave the inflorescence which is a great place to stay is that the spathes close and force the beetles up along the spadix. Once above the male zone, they will eat some of the pollen.  If they don't go up, they can finish by crashing the spathe against the spadix,  I observed it once in French Guiana.  So the plants "decide" when the pollinators arrive and depart."  The Cyclocephala beetles in Marc's photo can be seen near the bottom of a Philodendron spadix as they are eating pollen.  Of additional interest is the fact Marc now is close to scientifically proving the spadix is capable of attracting the pollinator beetles by producing a "glow" visible only to the insect as a result of infrared heat detected by the beetle's antennae rather than visually. 

Since the majority of aroids require a very specific insect species to do the work of pollination if that Cyclocephala beetle is not present it is unlikely the plant will be naturally pollinated unless the species is capable of self pollination. There is another genus of smaller beetles known as Neelia that visit some aroid species but these beetles do not appear to feed nor mate on the inflorescence.  It appears Cyclocephala beetles do almost all the work of aroid pollination. 
The Cyclocephala pollinators are members of subfamily Dynastinae in the family Scarabaeidae (thus "scarab beetles) and most belong to the genus Cyclocephala.  Some of these beetles are not particularly species specific and visit more than a single species or genus however it is surmised the height of the plant from the ground may be a particular attractant to individual beetles thus causing them not to cross pollinate other than their naturally specified plant species.   However, human induced cross pollination is not only possible but is frequently accomplished.

The beetles are generally drawn to the inflorescence in the late day or at dusk and are attracted by a combination of pheromones (scent) and a source of food and shelter which is composed at least in part of an oil produced on the staminate flowers containing lipids along with the enclosure of the spathe.  Shelter may play a part since the male often brings along his mate in to breed at the same time.  Some species have sweet smelling pheromones while others show
no noticeable aroma.  This aroma is produced by the sterile male flowers on the inflorescence which are attempting to entice the pollinator and to the male of that insect species the scent may be similar to the same pheromone that attracts him to a mate when she is ready to be impregnated.  This point is not factually certain.
During both female and male anthesis the spathe of Philodendron species opens to provide space for protection and often entices these beetles to use that area for feeding along with a place to safely copulate.  At anthesis the open spathe of some Philodendron species provide protection from the elements including rain since the spathe blade is bent slightly forward to prevent rain falling directly into the spathe's tube.  The plant provides a source of nutrient rich lipids which is an excellent food source for the beetles but the plant also benefits since it will be pollinated.  It is not uncommon for the beetles to spend the night within the spathe and spadix of the host Philodendron and mating during this period is common.  Beetles are typically active during the first ten to twenty minutes after their arrival time when the pheromone scent production is strongest.  Copulation has been observed to be strongest immediately after arrival but the beetles tend to become less active and to eat much less as the spadix begins to cool.

So why do they spend the night?  Thermogenesis!  Quite simply, the spadix can warm enough to be noticeable to the touch and for the insects that may be tired from traveling long distances Pollen on Philodendron renauxii, Photo Copyright 2009 Steve Lucas, www.ExoticRainforest.comto perform their required tasks this additional source of heat in the rain forest creates a microclimate and may actually increase their metabolism and encourage them to explore all portions of the spathe and spadix.  A microclimatic zone of warmth is now being generated within the spathe that offers both comfort and protection along with food.  This feature alone may increase the chance of self pollination within the specimen, but another may inhibit the same. 

The thermogenesis produced by the plant during anthesis is simply a natural heat produced by many living beings and appears to stimulate the beetles into a period of copulation.   Of major interest, even though the effects of thermogenesis have been observed for over 200 years, not until relatively recently did anyone know the cause.  So what is the chemical cause?  Salicylic acid, the same compound used to manufacture aspirin!  The salicylic acid begins not only the heating process but also the production of the pheromones (scent).  This unique process is not limited to Araceae (aroids) but is also found in other plant genera.  Of interest, salicylic acid may also help to prevent self pollination which is an interesting contradiction in and of itself.
The thermogenesis (heat birth or heat production) caused by the salicylic acid appears to be one of the stimulators to cause the beetles to be active and as a result to both feed and copulate.  It is known the rate of thermogenesis (heat rise) is sometimes dramatic, however thermogenesis does not produce a consistent temperature since the highest temperatures appear to last only 20 to 40 minutes.  In fact, it may be the visit of the beetles that contributes to the effect botanists know as thermogenesis.  The presence of beetles appears to increase the temperature produced by the event and the temperature increase appears to increase the amount of pheromone (perfume) being exuded by the tiny flowers.  Up to 200 beetles at a single time have been observed on a single Philodendron inflorescence during anthesis, however, the normal number is closer to 5 to 10.  Researchers have noted the highest temperatures appear to occur during the period when the highest number of beetles are present.   However the exact role of thermogenesis is still not well understood.  The pheromones (scent or perfume) produced by Philodendron species are not always detectable to the human nose. Some species have noticeably sweet scents in the early evening while some exude no noticeable smell on the first day of sexual anthesis.  On other species the pheromone is noticeable only during specific hours of the day, normally in the evening.  Most Philodendron produce their own unique pheromone which is attractive to only a single species of pollinating beetle.

A more recent train of thought includes the likelihood infrared heat acts as an increaser to the production and distribution of the pheromones.  Aroid pollination expert Dr. Marc Gibernau (GHEE-ber-no) of the University Paul Sabatier in Toulouse, France created and provided the chart below.  His chart (below) shows just how "bright" the "glow" of infrared heat is the the pollinating beetle as well as indicating the increase in temperature of the spadix above the ambient temperature of the rain forest.  Marc is shown standing next to the glowing inflorescence.  A discussion of infrared heat and its relationship to pollination follows the chart.

Alocasia cucullata inflorescence with pollen, Photo Copyright 2010 Steve Lucas, www.ExoticRainforest.comMarc suspects the beetles are also attracted to the spadix in the darkness of the forest due to the infrared heat produced during sexual anthesis.  In both private and public discussions with Marc in Miami, FL in September, 2008 he explained in a presentation to the International Aroid Society as well as to several of those of us (Julius Boos, Christopher Rogers and Steve Lucas) individually there is a significant increase in temperature above the ambient temperature of the rain forest at night once the inflorescence reaches anthesis.   The average Philodendron temperature increase is approximately 12 degrees Celsius (a 21.6 degree Fahrenheit increase) above ambient but a few plant species can increase in temperature by as much as 20 degrees C (36 degrees F) above ambient.  The heat can be so intense it can be felt on the palm of an opened hand held in front of the spadix which we have personally experienced.   On the chart below the spadix shown is Philodendron solimoesense.  If you notice the temperature gradients you will see the spadix of Philodendron solimoesense increases in temperature 14 degrees C or 25.2 degrees F above the surrounding rain forest ambient temperature.







This graphic is the Copyrighted property of Dr. Marc Gibernau, University Paul Sabatier in Toulouse, France and may not be reused without written permission

In photographic documentation seen on the chart (above) created with an infrared camera the "glow" of a sexually mature Philodendron solimoesense spadix is "visible" and Marc theorizes the beetles can detect that infrared heat with a method similar to a pilot seeing the glow of a runway light at night.  Since the beetle uses the spathe and spadix as a source of food (pollen) and a place for warmth during its own sexual reproduction the "glow" is an open invitation to fly to that source of food, shelter and warmth. 

At present, Marc and his associates are working to prove the beetle does not actually "see" the infrared heat, but instead detects it with receptors on their antennae or bodies instead of seeing it with their eyes. 

Marc forwarded these additional comments in a personal email received on October 14, 2008:  "My picture (below) is an inflorescence of Philodendron solimoesense.  Your paragraph  about anthesis may also need to explain the time shift between male and female phases (protogyny) because people may think an inflorescence can self-pollinate.  On day one the female flowers are receptive and the next day the male flowers produce pollen because the flower are synchronized.  On the first day the inflorescence is at the female stage and all stigma are receptive Cyclocephala beetles feeding on Philodendron pollen, Photo Copyright 2008, Marc Gibernau, Francefor fecundation/pollination by pollen grains.  On the next day (2nd day), the stigma are no longer receptive but the anthers are fully ripe (mature) and shed the pollen.  In a few species, such as in some Anthurium, these two sexual phases are overlapping and self-pollination may occur.  Hence, aroids need pollen vectors (insects) for pollination between different inflorescences.  The Cyclocephala beetles carry the pollen from a male-stage inflorescence to a female-stage inflorescence.  From the standpoint of a botanist the aroid reproductive structure would be the same as to view the inflorescence, which is composed of many flowers packed together, to functionally "behaves" like a flower."  As a result of the Cyclocephala beetle bringing pollen from one aroid species to another aroid of the same species the specimen is able to grow viable seeds. 

I asked Marc how the beetles find the inflorescence in the dark of the forest and was told the two attractants appear to work together.  First, since the pheromone produced by inflorescence can travel on the wind for 200 meters or so the beetles apparently first detect the scent in the wind.  But since the wind shifts through the forest they have to fly a zig zag pattern back and forth in to follow it to the source.  Once they are close enough to "see" the "glow" of the infrared heat they are drawn to the source in the same way a pilot sees his destination runway and simply follows the "lights" home. 

You can find more information on Philodendron species by clicking this link.




Forced commercial inflorescence inducement

Aroids produce their inflorescences depending on the time of year and season nature has predetermined.  Some species produce a spathe and spadix only during the dry or wet season in their natural habitat while others freely produce an inflorescence any time of the year.   Hybridized forms of Anthurium andreanum (Flamingo Flower) as well as hybridized Spathiphyllum (Peace Lilies) commonly sold in garden centers and discount centers can be seen with an open inflorescence virtually any month of the year. 

The commercial growers that produce these plants use a chemical known as gibberellic acid often sold as GA3 to induce the plants to produce an inflorescences in order to make them more saleable at the time a buyer sees one in the store.  Gibberellic acid is natural plant hormone and is used in agriculture to stimulate both cell division and cell elongation that affects the leaves as well as stems of a plant.  The continued use of the chemical in agriculture eventually affects fruit development.  Since the fruit of an aroid is produced on the spadix gibberellic acid thus speeds up the the production of inflorescences. 

Gibberellic acid is used commercially to make all the plants in one group bloom at the same time.  Through repeated use these large growers force the natural growth of a spathe and spadix regardless of season.  They have calculated the quantity to be used and know how much gibberellic acid to apply to any particular species but these formulations are often guarded secrets. 

An article by Dr. Paul Resslar on the production of an inflorescence of Caladium humboldtii can be found in the IAS journal Aroideana, volume 31, where he discusses the amounts and methods of application used in his research.  In Dr. Resslar's experience the chemical also can result in deformities.  Deformity is considered a minor problem in commercial aroid production including double spathes, spadices with strange shapes, malformed leaves and other side effects.   One of the side effects may well be the plant becomes dependent on the chemical to induce the production of an inflorescence and flowers.  A presentation by aroid enthusiast Ted Held at the 2008 International Aroid Show in Miami pointed out these exact problems.

Discussions on these effects can be found on the International Aroid Society forum Aroid l by searching the archives of the forum on the internet.  Some of the world's best aroid botanists and experts do not find the use of the chemical to be wise.  As a result, the use of gibberellic acid by aroid collectors with no experience in chemical use is not advisable and Spathiphyllum inflorescence (Peace Lily), Photo Copyright 2010 Steve Lucas, www.ExoticRainforest.comshould be used with caution even though it will work.  The use is primarily not advised since collectors have no way of knowing how much of the chemical to apply to any particular specimen based on species or size.  But there are other problems.  The instructions on some of the containers of GA3 say to apply the chemical near the base of the plant but it also says boldly not to allow the chemical to come in contact with the roots!  Some material indicates this may not be accurate but the warning can be found on sometimes on the product itself.  Since the roots are at the base of the plant is is obvious the chemical can be dangerous to your plants.  Other potential problems stated in papers on the commercial use of GA3 indicate the chemical will increase plant height, slightly reduce leaf width, and soften stems during periods of low light during shorter days.  Still, commercial growers love the product because it increases their production and profit.

The next time you buy a beautiful Anthurium or Spathiphyllum at a discount store and find it begins to produce odd shaped leaves and spathes or rarely if ever produces an inflorescence once you get it home there may be a reason.  The specimen has very likely been fed gibberellic acid since it was nearing sexual maturity to force it to mature and bloom early.  Without the constant use of the hormone to induce inflorescence production the specimen cannot get its "fix" and as a result may rarely bloom again.  It has been "hooked" on the chemical!  Collectors should consider using the product with extreme caution.

Aroideana is the journal of the International Aroid Society and out of print copies can be ordered at




Artificial pollination

spathe and spadix of Anthurium regale, Photo Copyright 2006, Steve Lucas, www.ExoticRainforest.comTo achieve hand-pollination the pollen from a bloom of the same or a related species which is already at male anthesis must be transported.  In nature the event is completed by an insect pollinator that has been attracted by the bloom's odor but within cultivation it must be done manually.  The hand of man must perform the tasks of collecting the pollen and transferring it from one inflorescence which is experiencing male anthesis to another younger inflorescence which is at female anthesis. 
To accomplish this task within any group of aroids an artist's brush wetted with sterile water is used to collect and hold the pollen from the spadix on one plant and transfer it to the wet stigmas on the spadix of the second inflorescence of another plant which is now undergoing female anthesis.  If the pollination is successful the inflorescence will "hold" on the second plant and the fruit will begin to develop.   If the artificial pollination is truly a success this will become obvious as the female flowers enlarge to produce  berries.  Each berry ranging in color from red to orange through yellow, purple or white may contain a single large seed or several medium sized seeds which are surrounded by a pulp and skin which is often tasty depending on the genus and species involved.  The development time may be long and in some species may take more than a year from pollination to ripeness and seed maturity. 
Anthurium jenmanii seeds, Photo Copyright 2007, Steve Lucas, www.ExoticRainforest.comHand-pollination of any aroid species can be accomplished relatively simply by collecting pollen from one bloom using a small brush such as a camel hair artist brush wetted with sterile water and transferring this pollen to a bloom as soon as it is observed the second is beginning to open.  Be careful to observe for the sticky liquid exuded by the female flowers once ready to accept the pollen.  Coating the female flowers with as much pollen as possible will act to ensure the pollen "holds" and the reproductive cycle is complete. 
Although not foolproof, it is possible to collect and store pollen for periods several months and possible up to one year by simply sweeping any excess pollen into a small glass tube that can be tightly capped.  The tube should contain a small amount of desiccant to prevent moisture from reaching the stored pollen.  If you only have a single specimen producing pollen and none to which the pollen can be transferred simply sweep the spadix and brush the pollen with a totally dry brush pushing the pollen grains into the test tube.  If the pollen comes in contact with moisture it will not remain viable.  Cap the tube tightly and store the labeled tube in a freezer.  Once another spadix develops and enters female anthesis take the tube from the freezer a few hours before use and warm it slowly to room temperature.  If you use it within one year the chances are fair it will be viable, however this method does not always work in every case.  However, pollination and hybridization researcher LariAnn Garner does not recommended freezing Philodendron or Caladium species which produce a wet strings of pollen.  The ability to store these types frozen for long periods of time are likely to fail.
In the case of unisexual imperfect flowers such as Philodendron, Alocasia, Colocasia, Caladium species etc. you may need to create a thick "pollen soup" and slowly introduce  it into the female floral chamber as soon as the restriction is loosened.  Be sure and tape the edges of the spathe closed for at least 16 minutes to keep the liquefied pollen from leaking out, but don't forget to remove the tape.  In many Philodendron and other species the spathe is only partially open at the time the female flowers are fertile and reach anthesis.  The pollinating Cyclocephala beetle does not care if the spathe is open since they can force their way through the restriction in order to enter the closed spathe. 
Successful growers have learned it is possible to use a vial of viable pollen and mix a small amount of sterile water with the pollen to create a "slurry".  This slurry can then be dribbled with an eye dropper down the sides of the spadix through the small opening at the top of the spathe as soon as the heat of thermogenesis and the pheromone is detected.  With luck you may be able to pollinate the hidden female flowers inside the floral chamber.
The International Aroid Society is now working to establish a database of serious member/collectors who have viable pollen in storage.  This project will eventually include providing appropriate testing material to verify the pollen is viable as well as pollen sharing among IAS members.

For Information on joining the International Aroid Society please click this link.


Want to see the development of a Philodendron spathe and spadix? 

How to grow Anthurium species

Watch pollen develop!  78 Days of the Anthurium regale reproductive cycle.

Species in the Exotic Rainforest Collection
Terms you may encounter in further research:
Anther - (AN-ther)
The part of the stamen where the pollen is produced and contained
Anthesis - (an-THE-sis) 
The period during which a flower is fully open and functional.  The time of pollination or bloom.
Inflorescence - (in-flor-ES-ence)
A group or cluster of flowers on a branch of a plant, in botany used to describe the structure of a spathe and spadix

Infructescence - (in-fruc-TES-sence)
The fruiting stage of an inflorescence

Nectar - (NEC-tar)
The exudate produced by the spadix in to attract pollinators

Perigone - (PERU-gown)
Collective term for the outer parts of a flower (parts of the spadix in this case) enclosing the stamens and pistils

Pheromones (fer-UH-mones)
A scent produced by the spadix during anthesis to attract insect pollinators and distribute pollen.

Pistil - (PIS-til)

The female, ovule-bearing organ of a flower, including the stigma, style, and ovary
Pollen - (POL-in)
sometimes incorrectly called flower sperm, is a fine to coarse powder consisting of pollen grains which produce the male
gametes (sperm cells) of seed plants
Stamen - (STA-men)
 Male reproductive parts of a flower

Stigma - (STIG-ma)
The pollen receptive surface, usually sticky, where the pollen enters the pistil. Usually the stigma will bear a sweet
solution which can attract insects to the sticky surface of the stigma where pollen is received and on which pollen

Stigmatic Hairs (stig-MAT-ic)
Hairs at the end of the stigmas designed to entrap the pollen grains.  These trichomes may also induce germination of the pollen grains.