Poplars to Become More Popular
By Neil Moran
Plants never cease to amaze me. And one amazing plant may be growing right in your backyard. Poplar trees, which are included in the populus species, include aspen, poplars and cottonwoods. While perhaps not one of the most sought-after trees for ornamental purposes (although there are several cultivated varieties bred for homeowners), the poplar tree is quickly becoming one of the most important species of trees for cleaning up industrial and wastewater pollution.
In a process called phytoremediation, poplar trees are being used from coast to coast to clean up and restore abandoned mining areas to normal by planting over sites that have been strip-mined. Poplar trees have been used for decades as wood pulp, but are now recognized as water pumping machines. Poplars have an amazing ability to grow deep roots. In fact, they are phreatophytic plants, meaning their roots extend all the way to the water table. Drawing as they do from the “zone of saturation” makes them capable of pumping pollutants out of contaminated areas. A five year-old poplar tree can pump up to 50 gallons of water per day.
While poplars aren’t currently being used in any high-profile phytoremediation projects around the Bay area, homeowners could take the lead in using poplars to clean up suspected contaminants in their yards, or even as a preventive measure by installing what is called a riparian buffer. If you suspect contaminants in your soil you could plant poplars as a means to clean up the contamination. And if you’re concerned with keeping the Bay clean for present and future use one could very easily establish a riparian buffer. A homeowner can simply plant poplars near the shore of a waterway, such as the Bay and its tributaries. The roots of the poplars would actually help to prevent contaminants, such as lawn fertilizers and pesticides, from seeping into the waterways. This was actually proven in a study that was undertaken by engineers at the University of Iowa. In the study, nitrates were measured from areas buffered with poplars and those that were not buffered with poplars. The results indicated a marked reduction in nitrates measured in the buffered areas.
In addition to phytoremediation, poplar trees can be grown as biomass for fuel and to make paper. There are advantages of using poplar trees as opposed to other plants for phytoremediation and as biomass. For one thing, poplars are not part of the food chain. They also grow fast, up to five meters per year. They are also easily propagated by cuttings, i.e., by cutting off a five-to-six-inch piece of stem and inserting it in a rooting medium. Poplars will also easily regenerate from stumps of felled trees. Finally, poplar trees are less expensive than other ornamental trees. Because they do grow so fast and aren’t in peak demand, they are sold for less than more popular (no pun intended) ornamental trees, such as Japanese Maple.
Many garden catalogs include poplar trees in their offerings. Take a close look at what you’re purchasing, because they do come in different varieties, some that have very attractive bark and foliage. Whatever you choose there couldn’t be a better time of year for improving your landscape with a tree that can not only beautify your property but will more than earn its keep with its contribution to cleaning up the water and soil in and around the Bay area.
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