What is Pteris?

Pteris, colloquially known as brake, is a genus of about 280 species of fern. Pteris species are native to tropical and subtropical regions around the world. Many of the smaller species are commonly kept as house plants and called "table ferns." Pteris species are popular as garden plants as well.

Some Pteris species grow in a very limited geographical range. Perhaps the most extreme example is the critically endangered fern P. adscensionis, which grows only on Ascension Island, a small volcanic island in the South Atlantic Ocean. There are only an estimated 500 P. adscensionis plants remaining in the wild due to habitat loss. P. umbrosa, or the jungle brake, has a native range limited to the rain forests of eastern Australia, where it grows in large colonies.

There are about seven Australian Pteris ferns, including P. tremula, commonly called Australian brake, tender brake, or shaking brake. The species name tremula means "shaking" or "trembling." The species is known for its pale green, lacy fronds.

P. tremula is native to sheltered rain forest and wet sclerophyll environments of Australia and the surrounding islands. It was reportedly the most commonly cultivated Pteris species grown in the United States during the 1950s. There are four horticultural varieties of P. tremula: caudata, minor, pectinata, and tremula. The plant prefers shade and filtered morning light, and grows best in moderately drained soil that retains some water.

P. vittata, commonly called the ladder brake or Chinese brake, is considered an invasive species in the United States, where it grows in the southern states, ranging from Texas to Florida, Georgia, and South Carolina. It is also grown in parts of California and Hawaii. P. vittata is a hyperaccumulator of arsenic in the soil, meaning it absorbs large amounts of the chemical. This ability of P. vittata was discovered by Dr. Lena Q. Ma of the University of Florida, who studied a ladder brake plant growing in an area of central Florida with heavy soil concentrations of copper arsenate.

Many Pteris species have been discovered to hyperaccumulate arsenic, including P. cretica and P. multifida. Not all Pteris ferns share this trait, however. For example, P. tremula does not tolerate soil with a high arsenic content. In addition, ferns belonging to other genera may be hyperaccumulators of arsenic. Scientists hope that such plants can be used in bioremediation efforts to remove excess arsenic from contaminated soils.