For the Venezuelan band, see Guaco .

For the piece of ancient pottery see Huaco (pottery)

Gauco, huaco, or guao, also vejuco and bejuco are terms applied to various Central and South American, and West Indian plants, reputed to have curative powers.

Native Americans and Colombians believe that the guaco was named after a species of kite, in imitation of its cry, which they say it uses to attract the snakes which it feeds on. Tradition says that the plant's powers as an antidote were discovered through watching the bird eat the leaves, and even spread the juice on its wings, before attacking the snakes.

Any twining plant with a heart-shaped leaf, white and green above and purple beneath, is called a guaco by Native Americans (R. Spruce, in Howards Nueva Quinologia, Cinchona succirubra, p. 22, note), which does not necessarily coincide with which plants are "true" guacos, as far as natuaralists are concerned.

What is most commonly recognized in Colombia as guaco, or Vejuco del guaco, would appear to be Mikania Guace (Humboldt and Bonpland, Fl. equinox. i~. 84, p1. 105, 1809), a climbing Composite plant of the family Eupatoriaceae , preferring moist and shady situations, and having a much-branched and deep-growing root, variegated, serrated, opposite leaves and dull white flowers, in axillary clusters. The whole plant emits a disagreeable odour.

It is stated that the Central American natives, after taking guaco, catch with impunity the most dangerous snakes, which writhe in their hands as though touched by a hot iron (B. Seemanii Hookers Journ. of Bet. v. 76, 1853). The odour alone of guaco, has been said to cause, in snakes, a state of stupor; and Humboldt, who observed that proximity of a rod steeped in guaco-juice was obnoxious to the venomous Coluber corallinus , was of opinion that inoculation with it gives perspiration an odour which makes reptiles unwilling to bite. The drug is not used in modern medicine.