Philodendron

Philodendron is a large genus of flowering plants belonging to the Araceae family. It ranks as the second-largest genus within this family, behind only *Anthurium*. Many species are cultivated as ornamental houseplants. The name comes from Greek, combining *philo-* (love, affection) and *dendron* (tree).

The genus displays an exceptionally wide range of growth habits. Plants can be epiphytic, hemiepiphytic, or, rarely, terrestrial, and some shift between these forms depending on conditions. Primary hemiepiphytes begin life high in the canopy as epiphytes; once large enough, they send aerial roots down to the forest floor to access soil nutrients. Some of these species form symbiotic relationships with ants, hosting ant nests among their roots and secreting nectar from extrafloral nectaries to attract them. In return, the plant gains nutrients from the nest and protection from insect herbivores. Secondary hemiepiphytes start on the ground or low on a tree trunk, rooting in soil before climbing upward. They may eventually become fully epiphytic, losing their ground roots. Those not initially near a tree grow along the ground with long internodes, moving toward darker areas (scototropism) to locate a tree. Once a tree is found, they switch to phototropic growth, with shorter, thicker internodes. A few species, like *Philodendron fragrantissimum*, alternate between clumps of leaves with short internodes and long, bare internodes over a meter in length.

During flowering, some species produce three temperature peaks. This heat attracts beetles inside the spathe and increases the chance they become coated with pollen. A sticky resin, unique to *Philodendron* and *Monstera* among Araceae, forms on the spadix to help pollen adhere to beetles. The resin also appears on stems, leaves, and roots, and may be red, orange, yellow, or colorless when fresh, turning brown upon exposure to air. Thermogenesis may also encourage beetles to mate and helps disperse pheromones. The spadix is held at a 45-degree angle to the spathe, likely to maximize heat-driven pheromone dispersal. The heat comes from oxidizing stored carbohydrates and lipids in the sterile zone of the spadix. Carbohydrates are used first; once peak temperature is reached, lipids are oxidized directly. The reaction is triggered by acetosalicytic acid in the sterile zone, which causes mitochondria to switch to a cyanide-resistant electron transport chain, producing heat. Philodendrons consume oxygen at a remarkably high rate during this process, comparable to hummingbirds and sphinx moths, and the spadix emits infrared radiation.

Leaves are typically large and striking, often lobed, deeply cut, or pinnate. Shapes vary widely, from oval (as in *Philodendron* 'White Princess') to spear-shaped or divided (as in *Philodendron tripartitum*). Leaves grow alternately on the stem. A key trait is that a single plant produces different juvenile and adult leaves. Seedling leaves are usually heart-shaped, then mature into juvenile leaves, and later into adult leaves through a gradual process called metamorphosis. Adult leaves are generally much larger and can differ significantly in shape, which has historically caused taxonomic confusion.