The pau d'arco (Tabebuia impetiginosa (Martius ex de Candolle) Standley) is a member of the Bignoniaceae known as the trumpet vine family for its large number of profusely flowering vines. There are 113 genera in the family with around 800 species. The family has its share of colorful trees and shrubs; Tabebuia alone comprises 100 species of the family. (A Guide to Flowering Plant Families, Wendy B. Zomlefer, University of North Carolina Press, 1994)
The "Lapacho group" of the Tabebuia are huge trees known for their hard, weather- and insect-resistant lumber variously called pau d'arco, ipé, lapacho, or yellow poui. The famous boardwalk in Atlantic City is made of Tabebuia lumber.
Native to Brazil, Tabebuia impetiginosa [ta be bu' ya im pet' e gi no' sah] loses its leaves during the dry season (tropical winter). It blooms before setting new leaves. In its native habitat, blooming when few leaves are present probably serves to attract more pollinators. Carpenter bees are thought the primary pollinators, but the Arizona-Sonora Desert Museum reports that two species of hummingbirds visit their pau d'arco. In west-central Florida, bloom-time is late January and February.
The tree was first 'discovered' by European science during the 1817 to 1820 Austrian Commission, an exploration of Brazil by Johann Baptist von Spix, a zoologist, and Carl Friedrich Philipp von Martius, a botanist. In that time, Martius collected 12,000 herbarium specimens for study back in Europe. Augustin Pyramus de Candolle named it Tecoma impetiginosa in 1845. (The generic name was established by Antoine Laurent de Jussieu in 1789; he took the name from tecomaxochitl, a Nahautl (Aztec) name meaning pot-tree flower.)
Paul Carpenter Standley moved the tree to the genus Tabebuia in 1936. Tabebuya was the aboriginal name meaning antwood, perhaps meaning a wood that resisted ant damage. (Composition of Scientific Words, Roland Wilbur Brown, Smithsonian Institution Press, 1991 and W3 Tropicos, Jim Solomon, Missouri Botanical Garden)
The species epithet, impetiginosa, refers to impetigo, a skin eruption. Today, impetigo refers to those skin infections caused by Streptococcus or Staphylococcus bacteria. The contagious infection is usually found around the mouth and nose and is most often seen in children during hot summer months. Pau d'arco has antifungal and antimicrobial properties and may have been used against impetigo. But impetigo can set in after a rash has allowed bacteria to enter the skin and contact with freshly cut Tabebuia wood can cause a severe rash. No sources have been found as to whether the name refers to a cause of or a cure for impetigo.
The common name, pau d'arco, is Portuguese meaning bow wood. Natives made hunting bows from the dense resilient wood found in many of the Tabebuia species. The wood is still used for training weapons especially in the martial arts.
Pau d'arco as an "herbal tea" actually refers to bark from three species of Tabebuia. There are not any set standards as to precisely what pau d'arco contains, but there are numerous folkloric claims to the remedial powers. Chemical studies have discovered 51 chemicals in Tabebuia impetiginosa. Memorial Sloan-Kettering Cancer Center warns against its use citing adverse effects--nausea, vomiting, dizziness, and anemia.
