Tamara Bonnemaison writes today’s entry, which features a representative of a family never previously highlighted on Botany Photo of the Day, the Pontederiaceae:
Today, regular BPotD contributor 3Point141 (3Point141@Flickr) shares his striking photo of Pontederia cordata, taken on the shoreline of Turkey Lake, Orlando, Florida, USA. Rusty Clark ((Rusty Clark@Flickr) also contributed her image of the species in flower. Thank you to both contributors!
Pontederia cordata, or pickerelweed, is a rhizomatous, emergent perennial that grows in wetlands from Argentina north to eastern Canada. It typically has lance-shaped leaves with rounded lobes, but the leaf shape in particular is quite variable and has led to the naming of several now-synonymized varieties. From June through November in eastern North America, pickerelweed sends up a large spike displaying hundreds of light blue flowers. This species grows prolifically and forms dense stands that, when blooming, are stunning in the wild and in garden ponds. To get an idea of how impressive a stand of pickerelweed in bloom can be, have a look at the fourth image shown on Dr. Spencer Barret’s lab’s site on floral displays.
Pickerelweed is common, is adapted to a wide range of wetland conditions, and grows rapidly and aggressively – traits that make the species useful in constructed wetlands in North America. Collins, Sharitz and Coughlin’s (2005) study, titled “Elemental Composition of Native Wetland Plants in Constructed Mesocosm Treatment Wetlands” examines the beneficial role that Pontederia cordata can play in treating runoff from coal-fired power plants. Power plant runoff is both high in heavy metals and acidity, and the species selected for constructed wetlands treating this runoff must be able to survive such difficult conditions. Collins et al. found that Pontederia coradata was able to establish in shallow wetlands receiving acidic and polluted runoff, and was successful in taking up a moderate amount of heavy metals. Pickerelweed and the rush species, Juncus effusus, were particularly effective in accumulating iron and aluminum. Constructed wetlands can be used to treat water contaminated by many sources, and Pontederia cordata is being examined as one of an assemblage of plants that can be used to remove organic solvents, phosphorus, and other contaminants.
The characteristics that make pickerelweed useful in North American wetlands urge caution in other parts of the world. The species’ aggressive nature has allowed it to become invasive in some countries, including Kenya. It has naturalized, though is not recognized as invasive, in areas of Europe, Australia and western North America.