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Philodendron sp. Schott 1829
pronounced: fill-oh-DEN-dron species
(Araceae – the arum family)
common name: Philodendron
Philodendron is derived from two Greek words, φιλο- (philo-), love, and δενδρον (dendron), a tree. Taxonomically the genus is still poorly known, with many undescribed species. Many are grown as ornamental and indoor plants.
These can be found in many diverse habitats in the tropical Americas and the West Indies. Most occur in humid tropical forests, but can also be found in swamps and on river banks, roadsides, and rock outcrops, in a diverse range of elevations from sea level to over 2,000 m. Species of this genus are often found clambering over other plants, or climbing the trunks of trees with the aid of aerial roots. They usually distinguish themselves in their environment by their large numbers compared with other plants, making them a highly noticeable component of the ecosystems in which they are found. Although they can be found also in Australia, some Pacific islands, Africa and Asia, they are not indigenous to these regions, but have been introduced, often as garden escapees.
Compared with other genera of the Araceae, Philodendrons have an extremely diverse array of methods by which they grow. They can be epiphytic, hemi-epiphytic, or terrestrial, although very few grow terrestrially. Some show a combination of these growth habits, depending on the environment. Hemi-epiphytic Philodendrons can be classified into two types: primary and secondary. The former start life high up in the canopy where the seed initially sprouts. The plant then grows as an epiphyte. Once it has reached a sufficient size and age, it will begin producing aerial roots that grow towards the forest floor. Once the roots have reached the forest floor, nutrients can be obtained directly from the soil. The plant’s strategy is to obtain light early in its life at the expense of nutrients. Some primary epiphytic species have a symbiotic relationship with ants. The ants’ nest is built among the plant’s roots, which help keep the nest together. Philodendrons have extra-floral nectaries, glands which secrete nectar that attracts the ants. The plant in turn obtains nutrients from the ants’ nest, and the aggressive nature of the ants helps protects the plant from other insects that would eat it.
Secondary hemi-epiphytes start life on the ground, or on a tree trunk close to the ground, and have their roots in the soil very early in their lives. They then begin to climb up a tree, and eventually may become completely epiphytic, doing away with their subterranean roots. They don’t always, in fact, start their lives close to a tree. Some Philodendrons grow with long internodes along the ground until a tree is found. They find a suitable tree by growing towards darker areas such as a tree’s dark shadow. This trait is called scototropism [σκοτος (skotos), dark – growth towards the dark]. Once the tree has been found, this scototropic behaviour stops, and a phototropic [φως, φωτος (phos, photos), light – growth towards the light] growth habit is adopted. The internodes then shorten and thicken.
The leaves are usually large and imposing, often lobed or deeply cut, and may be more-or-less pinnate. They can also be oval, hastate, or with many other possible variations. The leaves are borne alternately on the stem. The same plant carries two types of leaves at the same time – juvenile and adult – that can be drastically different from one another. The leaves of the seedling plants are usually cordate. Early in the plant’s life, but after it has got past the seedling stage, the leaves will have acquired the typical juvenile leaf’s shape and size. Later in life, it starts producing adult leaves, a process called metamorphosis. Most Philodendrons go through this process gradually: there is no immediate distinct difference between the juvenile and the adult leaves. As well as their being typically much bigger than the juvenile leaves, the shape of the adult leaves can be significantly different. Incidentally, this difference in shape is one of the reasons for the taxonomic confusion surrounding this genus – plants have been mistakenly classified as different species when they are actually the same. The mechanism that triggers the leaf changes can vary considerably. One trigger can be the height of the plant. Primary hemi-epiphytes, as mentioned earlier, start off on the dark forest floor and climb their way up a tree, displaying their juvenile type leaves along the way. When they are close enough to the forest canopy for the light to be brighter, the larger adult leaves are formed to take advantage of this improvement in the light. Secondary hemi-epiphytes have a different trigger: the juvenile leaves suffice until the roots reach the soil, and the increase of nutrients then causes the plant to develop its adult leaves and rapidly gain in size. Another interesting qualify of Philodendron leaves is that they are often quite different in shape and size even between two plants of the same species – another cause of taxonomic confusion.
The inflorescence is a spathe and spadix. Depending on the species, there can be anything from a single inflorescence up to a cluster of 11. The spathe tends to be waxy, and is usually bicoloured. In some species the base of the spathe is a contrasting colour with the upper part, and in others the inner and outer surfaces are of different colours. The paler colour tends to be either white or green, and the darker usually red or crimson. The spadix is usually white, and shorter than the spathe. On the spadix are fertile female, fertile male, and sterile male flowers. The sterile male flowers form a barrier between the fertile males and the fertile females, to prevent fertilization within the same inflorescence. Often, as an added precaution, the female flowers are not ready for fertilization when the males of the same inflorescence are producing pollen. Reproduction is achieved by means of beetles, with many Philodendron species requiring the presence of a specific beetle species to achieve pollination. Unlike the pollinating wasps of many of the fig species, these particular beetles do not confine themselves to Philodendrons, but also pollinate other genera. In order to attract the beetles, the sterile male flowers give off pheromones, chemical factors that trigger a social response in members of the same species [from Greek φερω (phero), to bear + hormone from 'ορμη (horme), impetus].Those given off by the sterile male flowers are thought to imitate the pheromones given out by the female of the beetle species – the fertilization of the plant is done by male beetles. Towards the end of the pollen production of the inflorescence, the spathe begins to close up from the bottom, forcing the beetles to move up and across the fertile male flowers situated at the top end of the spadix. Having crawled over the pollen, the beetles become covered in it, and deposit it when they crawl into another inflorescence. The beetles feed on the pollen, and also eat the sterile male flowers, which are rich in lipids, compounds which contain fats and oils.
The fruit produced is a berry. The spathe enlarges to hold the maturing berries. Once the fruits are mature, the spathe will begin to open again, and it will then break off at the base and fall to the forest floor. The seeds within the berries are tiny. The berries of some species of Philodendrons give off odours to attract animals to eat them and disperse the seeds. Possible dispersers include bats and monkeys.
Photographs taken in Picnic Bay 2010
Page last updated 18th January 2017