Fight soil pollution with resilient fern, which has been here for millions of years

Maureen Gilmer | Special to The Desert Sun

Phytoremediation is the science of using plants to help clean up pollution. After all, plants are experts at selectively extracting nutrients and minerals from the soil through their roots. So why can't they be used to remove toxins too? Scientists have tested many species for their ability to reduce toxicity in soils, air and water. Among the most important phytoremediation plants are ferns.

This is because ferns are unique. They are relatively primitive, dominating the earth long before seed-bearing plants and flowers appeared. In fact, at one time great forests of monster ferns covered much of the globe, but climate change forced them to evolve into smaller sizes. They reproduce by microscopic spores typically held on the back or edge of the leaves.Each genus of fern arranges their spores in a different pattern, which is one way of distinguishing the all-too-similar species.

Because ferns were around since the age of dinosaurs, they have survived for hundreds of millions of years relatively unchanged. This requires a powerful ability to withstand cataclysmic climate change and survive. The toxins of volcanic eruptions and the cold of ice ages did not make them extinct like so many other plants we know today only by their fossil record.

One of the most important phytoremediation ferns is the Chinese break fern, Pteris vittata. It has been deemed a hyper-accumulator, which are rare plants with a much greater ability to take up heavy metals and other toxins from soil. This break fern is highly successful at extracting a specific toxin, arsenic. It can draw up arsenic at a rate seventeen times greater than that of other phytoremediation plants. Many other species of the genus Pteris have been designated hyper-accumulators as well.

We are just waking up to the potential for arsenic toxicity in the backyard. Because this toxic substance kills insects, bacteria and fungi, it has long been used as a wood preservative. Where arsenic treated wood has existed in the yards of older homes in the form of fence posts or deck foundations; decomposing wood can leave a concentration of arsenic behind after the structure has vanished.

Arsenic may be present in the soil if your subdivision is located on the former industrial site of metal manufacturing. Homes built on land that was formerly for orchards may also find traces of arsenic once used as pesticide. During the 19th century, arsenic was a common pesticide and it may be present on the grounds of Victorian homes.

Another large study was conducted to try and solve the growing problem of formaldehyde emission concentration indoors. Its source is many types of pressed wood products that use adhesives containing urea-formaldehyde. This form of the chemical is also present in foam insulation and some textiles.

Scientists tested 85 species of house plants to see if they would phytoremediate formaldehyde concentrations indoors. Of five classes of plants tested, the ferns proved far more capable than any other group. Of these, the Japanese Royal Fern. or Osmunda japonica, was fifty times more effective than the least capable plant. Other ferns deemed effective to a lesser extent are hare's-foot fern, Davallia mariesii, spider fern, Pteris multifida and Polypodium formosanum.

In the past we saw indoor Boston ferns as beautiful green foliage plants. Today they are elevated to hard working pollution fighters. Maidenhair ferns, bird's-nest ferns and Japanese painted ferns are perfectly sized for indoors as well. Shop for them in greenhouses and florist shops for smaller sizes that fit easily into all your rooms for house-wide phytoremediation.

For those with new homes or wherever formaldehyde emissions are expected, grow ferns in pots throughout the house. They cannot grow in our desert heat but are easy indoors as shade lovers in the garden. This new science of phytoremediation is a beautiful example of how nature tailored certain plants to clean her earthy carpets, and now they'll do the same for yours.