Described to science in 1913, Philodendron callosum is found in Venezuela, the Guiana Shield, and northwestern Brazil, P. callosum is largely found as an epiphytic species growing on dead trees. epiphytes (ep-a-FIT) are those plant species that grow attached to another plant, in most cases a tree. But the epiphytic Philodendron callosum is botanically in a section of species that commonly grow on the ground and even on stone.  That Philodendron section is Philiopsammos.

 Almost all specimens in this section are limited to the Guiana Shield and the Amazon region near that part of northeastern South America. Rather than growing as epiphytes, species in sect. Philiopsammos are largely terrestrial or epipetric.  Epipetric species are those that grow on stone.  Section Philiopsammos includes approximately one dozen species, almost all are known to creep across the ground.   One common factor to species within this section is these Philodendron possess short internodes.   An internode is defined as the portion of stem between the plant's nodes.  The nodes are the places along a stem where leaves are placed.  Although Philodendron callosum is placed botanically in this section it tends to grow in the rain forest on dead trees as an epiphyte.  Philodendron species, and especially hybrid forms, 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 scientific principle of natural variation and morphogenesis.  Click here.

Dutch naturalist Joep Moonen (pronounced yupe) works in the rain forests of the Guiana Shield and lives in French Guiana. French Guiana is a relatively small country in the northeastern portion of the South American continent which bs on the Atlantic Ocean to the north and Brazil to the south.  In an email received in November, 2007 Joep indicated Philodendron callosum is quite rare within the region and is a "Nice small epiphyte with extra ordinary leaf surface tissue. (It is) Not common."   He continues in his brief note saying the species "loves to live on dead trees and feeds on the dead bark".   Later in the same message Joep stated P. callosum lives well "under ideal circumstances (with) lots of humidity and food (dead bark), grows well in direct sunlight and makes compact beautiful leaves."   It also "grows in the shade hanging on the trunks of living trees (growing) relatively long dark green leaves." Joep also stated P. callosum is not often found in flower in the rain forest. He pointed out, like some other epiphytes, the species does not grow well in a pot with plant soil. He is actually considering attempting to grow it strictly in sawdust.

When a Philodendron species is "in flower", the term is not used the same way as if one were speaking of a bed of perennial or annual flowers.  The "flowers" on a Philodendron are quite small, almost microscopic.  Aroid expert Julius Boos explains, "What usually is referred to as a flower on an aroid actually is a complex or combination of several different structures, and is referred to as an inflorescence. The spathe is actually just a modified leaf, sometimes attractively colored, which surrounds and protects the spike-like central spadix. The true and usually tiny flowers are located along the spadix."
Philodendron species are a uni-sexual genus.  Julius explains it best regarding Philodendron species, "The male and female flowers are situated in different areas, the female at the base of the spadix, then sterile flowers, then above them are the male, and in some species there is also a sterile zone at the top of the spadix."

Many Philodendron species are pollinated by a very specific insect "assigned" in nature to fulfill that purpose.  Mother nature uses these "assigned" insects to prevent cross pollination within a species and keep the species relatively pure.  Those "assigned" to pollinate a specific species are normally the males of the insect species and are drawn to the plant by a type of "perfume" known as a pheromone.  And in the case of Philodendron callosum, that insect species is known by botanists and entomolostists to be pollinated by a scarab beetle known scientifically as Cyclocephala rustica.

There are at least three known variations (forms) of Philodendron callosum.   But even though P. callosum does grow in nature primarily as an epiphytic species, it can and does grow on the ground.  In fact, the majority of collectors prefer to grow the species as a ground spreading species.   And despite the fact you can find references on the internet that indicate P. callosum is now "wild" within the Hawaiian islands, Hawaiian native, grower, and author Leland Miyano, who is an expert in aroids, palms, and cycads, made these observations regarding the species, "Philodendron callosum is not wild in Hawaii, but it grows well. There are three forms that I grow. There is the French Guiana form that is slightly rough, semi-coriaceous,with acuminate tips, and medium green blades. There is the Venezuelan form that is the most attractive in my opinion...dark green, very rough, rounded tips, and stiffly coriaceous. The other form is Philodendron callosum var. ptarianum, which was described as Philodendron ptarianum...oddly Kew accepts both names. It has leathery glaucous blades that are smooth. I grow mine as terrestrials in dirt...but it would grow as an epiphyte or on rocks as long as it is kept slightly moist."  In a separate message, Leland commented further about the species possibly thought by some in Hawaii to be Philodendron callosum  when he indicated perhaps the messages on the internet "is mistaking Elahoglossum ferns for the Philodendron. The common name is Maui's Paddle and Philodenron callosum has a similar paddle-shaped leaf. Specifically,the endemic species, Elaphoglossum crassifolium ( Gaudich.) W.R. Anderson & Crosby, has thick coriaceous leaves and grows as an epiphyte or terrestrially."

At present, we grow our specimen, which was a gift from Florida collector Christopher Mink, in extremely loose soil.  The soil mixture is composed of approximately 30% soil, 20% peat, 40% orchid bark with charcoal , 10% Perlite and some finely cut and shredded sphagnum moss works well.  We also make our own compost and add it in place of some of the peat when available.  This mixture is based on the fact this species appears to do best, at least in the rain forest, as an epiphyte with its roots exposed to the air.  This very loose mixture allows even more exposure to the atmosphere than would a mixture that stays constantly wet.  The mixture is kept damp, but never wet. However, we are seriously considering transferring our specimens into a large 30cm (12 inch) square wooden orchid box packed around the edges with sphagnum moss and filled completely with orchid potting medium.

If you enjoy spending time in a rain forest filled with exotic creatures and extremely rare exotic plant species Joep Moonen (pronounced yupe) also enjoys introducing people like you to the rainforests of northeast South America.   The Emerald Jungle Village website can be found at:  http://home.planet.nl/~gumamaus/   For eco-tour information and a brochure contact Joep Moonen (pronounced yupe) directly at EmeraldJungleVillage@wanadoo.fr