Philodendron species: Philodendron

Family

Araceae

Common Names

Philodendron, money plant, sweetheart vine.

Plant Description

This large and diversely complex genus of some 500 species is native to tropical America and the West Indies. In North America philodendrons are most frequently found as a house or garden plant. As a morphologically diverse genus, philodendrons can vary from small vine-like plants, to shrubs and large climbing species gaining considerable size in their natural tropical habitats. These evergreen plants have stout stems, often with and adventitious aerial roots that facilitate their climbing habit. Leaves are generally simple, dark green, leathery, heart or arrowhead-shaped, varying in size from a few inches to three to 4 ft. in length. In some species, the mature leaves become deeply load. In contrast to Monstera deliciosa (Ceriman), which is commonly mistaken for a philodendron, the leaves of philodendrons do not contain perforations or holes. Some species have red stems and purple-red new growth (Fig. 306, Fig. 307 and Fig. 308).

Philodendron scandens, a widely grown Mexican species with heart-shaped glossy green mature leaves, has immature foliage that is golden-brown. The fluorescence is a white, green, or yellow spathe often with red or purple margins overlapping to form tubes. The spadices are shorter than the spathes. Fruits are white or orange red berries. The common house and garden plant, pothos (Epipremnum species), is frequently mistaken for a philodendron.

Figure 306. Philodendron bipinnatifidum.

Figure 307. Philodendron scanders (variegated).

Figure 308. Philodendron species.

Toxic Principle and Mechanism of Action

Like other members of the Araceae family, Philodendron species contain oxalate crystals in the stems and leaves [1,2]. The calcium oxalate crystals (raphides) are contained in specialized cells referred to as idioblasts [1,2]. Raphides are long needle-like crystals bunched together in these specialized cells, and when the plant tissue is chewed by an animal, the crystals are extruded into the mouth and mucous membranes of the unfortunate animal. The raphides once embedded in the mucous membranes of the mouth cause an intense irritation and inflammation. Evidence exists to suggest that the oxalate crystals act as a means for introducing other toxic compounds from the plant such as prostaglandins, histamine, and proteolytic enzymes that mediate the inflammatory response [3]. (see Dieffenbachia species)

In addition to the contact irritant effects of the philodendrons, the plants appear to have nephrotoxic and neurotoxic properties, especially in cats [4-7]. Signs of renal failure do not appear until several days after the ingestion of the plant.

Risk Assessment

Philodendrons are frequently grown for their foliage and hardiness as house plants and consequently household pets have access to the plants.

Clinical Signs

Household pets that chew repeatedly on the leaves and stems of philodendrons may salivate excessively and vomit as a result of the irritant effects of the calcium oxalate crystals embedded in their oral mucous membranes. The painful swelling in the mouth may prevent the animal from eating for several days. Severe conjunctivitis may result if plant juices are rubbed in the eye. If a cat is known to have ingested the leaves, it should be monitored for signs of renal failure for several days and treated accordingly.

Treatment

Unless salivation and vomiting are excessive, treatment is seldom necessary. Anti inflammatory therapy may be necessary in cases where inflammation and edema of the mouth is severe. The plants should be removed or made inaccessible to the animals eating them.