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Economic Plant Photographs #24

Pokeweed: An Interesting American Vegetable

Pokeweed Family (Phytolaccaceae): Pokeweed

Pokeweed (Phytolacca americana) is a robust perennial potherb native to the eastern United States. It belongs to the pokeweed family (Phytolaccaceae), a small family found mostly in Africa and the New World. In addition to pokeweed, it also includes several enormous South American trees and some unusual serpentine vines of the tropics. Poke is derived from the Algonquian Indian word "pakon" or "puccoon," referring to a dye plant used for staining. It is sometimes spelled polk and the leaves were reportedly worn by enthusiastic supporters during the campaign of James K. Polk, 11th president of the United States. The generic name Phytolacca is derived from the Greek word phyton (plant) and the French lac (lake--a dark red pigment), referring to the crimson juice of ripe berries. Pokeweed may grow to nine feet tall, with large, alternate leaves and a carrotlike taproot. It may become a very invasive weed in southern California gardens and is difficult to eradicate when it becomes well-established. Greenish-white flowers are produced in long clusters (racemes) that droop due to the weight of ripening fruit. The flattened berries change from green to shiny purplish-black. Ripe berries yield a crimson juice that was used as a substitute for red ink and to enhance the color of pale wines. The coloring of wine with pokeweed berries has been discouraged because they are very poisonous.

Freshly cut young leaves and shoots may be cooked and eaten like spinach. They should be boiled twice, and the first water being discarded. In 1969, when astronaut Neil Armstrong walked on the moon, a popular song on the radio was "Poke Salad Annie." The song depicted a poor southern girl who picked a wild plant called pokeweed for a vegetable. The greens are also called poke salet, and they are sometimes canned and sold in markets.

Left: Flowering branch of pokeweed (Phytolacca americana) showing the characteristic dark green leaves and developing berries. Right: A can of poke salet greens, the young, tender leaves of pokeweed.

Left: Fruiting branch of pokeweed (Phytolacca americana) showing the characteristic dark green leaves and purple-black berries. Right: A can of poke salet greens, the young, tender leaves of pokeweed.
Several toxins have been identified in species of Phytolacca, usually concentrated in the roots, berries and seeds. These poisons include an alkaloid (phytolaccine), a resin (phytolaccatoxin), and a saponin (phytolaccigenin). According to W.H. Lewis and M.P.F. Elvin-Lewis (Medical Botany, 1977), the most serious health hazard from Phytolacca comes from a very toxic plant protein called a lectin. Lectins can cause red blood cells to clump together (agglutinate) and may stimulate abnormal cell division in quiescent B and T-lymphocytes. Lectins are the primary toxic principle in the world's deadliest seeds, including the castor bean (Ricinus communis) and prayer bead (Abrus precatorius). The agglutination property of lectins serves a useful purpose in legumes, by binding and localizing essential nitrogen-fixing bacteria within the swollen nodules of roots.

Phytolacca Family (Phytolaccaceae): Ombu Tree

But of all the species of Phytolacca, the most remarkable is the ombu tree (P. dioica) of the Argentine pampas. Ombu trees (also called umbu trees) grow to a height and spread of 60 feet (20 m) or more, often with multiple trunks developing from an enormous base resembling a giant pedestal. The huge base may be three to six feet tall (1-2 meters) and 95 feet (30 meters) in circumference. Ombu trees are native to the grassy pampas of Argentina, usually widely spaced and the only trees for miles. They are called "lighthouses of the pampas" by gauchos who use them for welcome landmarks and shelters. The massive, fire-resistant trunk contains water storage tissue, an excellent adaptation for raging grass fires that periodically sweep across the pampas. Even young trees develop the characteristic enlarged (caudiciform) base, an obvious advantage in surviving prolonged months of drought during the dry season. Several specimens of ombu trees are planted at the Palomar College Arboretum, including another interesting species from Peru (P. weberbaueri) and an unusual hybrid between the two species.

The North American pokeweed (P. americana) is synoecious, a term applied to a plant (or a species) in which the flowers are perfect (bisexual) with functional male stamens (androecium) and female pistil (gynoecium). Flowers of P. weberbaueri and a hybrid between P. weberbaueri and P. dioica are also bisexual, with a ring of numerous stamens (androecium) surrounding a multicarpellate gynoecium. Although the specific epithet for the umbu tree is dioica, the plant is not truly dioecious. In the Palomar College Arborteum, flowers of P. dioica have stamens (androecium) and a pistil (gynoecium) in the same flower, although racemes in fruit may be lacking evidence of stamens. In some flowers with mature stamens the gynoecium is not fully developed.

Left: Massive base of an ombu tree (Phytolacca dioica). Right: The foliage and inflorescences (racemes) of the ombu tree. The older, far right raceme is composed of numerous multicarpellate fruits, each representing a separate flower.

Close-up view of an immature, bisexual flower of Phytolacca dioica showing a central gynoecium (red arrow) surrounded by many stamens (androecium).

Phytolaccaceae: Phytolacca weberbaueri

Left: The Peruvian species Phytolacca weberbaueri in the Palomar College Arboretum showing the large base which is similar to the Argentine ombu tree (P. dioica). Right: A hybrid between P. weberbaueri and P. dioica in the Palomar College Arboretum. This large tree has developed a massive trunk greater than one meter in diameter in only 25 years.

The pokeweed family also includes some unusual tropical vines, mostly native to the Caribbean region, Central and South America. Agdestis clematidea is a climbing vine native to Mexico and Guatemala. It grows from a huge gray tuber weighing up to 150 pounds (68 kg) and resembling a large granite boulder. Another interesting species called hoop vine (Trichostigma octandrum) in native to the Virgin Islands. Like a woody boa constrictor, it trails along the forest floor, ascending tropical trees and often forming tangled masses of writhing serpentine branches. It is essentially leafless except on new growth where leaves are produced that superficially resemble pokeweed. Hoop vine is used in basketry on the island of St. John, a rare art that is only practiced today by a few native islanders. The tightly woven baskets are made entirely from strips of hoop vine and are masterful works of art.

Photos Of Hoop Vine On The Island Of St. John

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