Pontederia cordata

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.

Pontederia cordata
Pontederia cordata

10 responses to “Pontederia cordata”

  1. Lee Foote

    Great photo of a beautiful wetland plant. Thanks! I had to wonder if the common name “Pickerelweed” is another classic misnomer or whether the species really does overlap with the range of pickerel? Here, pickerel are the fish called pike or Esox lucius, but there may also be other fish of this name, possibly chain pickerel or sauger. The habitat in shallow water would make good pike cover.

  2. Clement Kent

    Ooops! “north to the eastern USA” you say, and then you point to Spencer Barrett’s photo of Pontederia blooming massively in Paugh Lake, Ontario, Canada.
    Check a map, and you’ll find that pickerelweed goes considerably to the north of eastern USA in Canada.
    I’ve seen it well to the north of the northern tip of Maine.

  3. Hugh Nourse

    We have seen this plant choking the tributaries to the Amazon River in Peru.

  4. Daniel Mosquin

    Thanks for pointing that out, Clement. That was my edit, so I take responsibility.
    I used the distributional range for Pontederia cordata on the USDA GRIN web site, which excluded any Canadian sites. What I (strangely) needed to do was click through to Pontederia cordata var. cordata to get the native Canadian sites included.
    As for the cognitive dissonance, I guess my only excuse is that I was doing the edits on a Friday evening at the end of another long week.

  5. Richard Old

    For distributional maps of North American plant species, the best place to find information is:
    USDA sites use the USDA PLANTS database which is obsolete.
    See: http://www.bonap.org/BONAP-PLANTS/BONAPvsPLANTS.html
    for a comparison of the two sites.

  6. Emma

    That is really an amazing photo! I want that flower in my garden! I hope that there is a place where I can buy it. Regards!

  7. Rusty Clark

    Thanks so much for including my photo of pickerelweed. It was, in fact, taken in my backyard. I collected a couple plants that had been washed up at a local lake by boat traffic, and it flourished in a large plastic planter full of water and a couple pet store feeder goldfish. It bloomed most of the summer.

  8. Daniel Mosquin

    Richard, I tend to use the distributional information from USDA GRIN, which I believe is a separate system from the USDA PLANTS database. I don’t know how that one compares, but I do recall GRIN being different from PLANTS in terms of taxonomic treatments.

  9. OrchidGrowinMan

    This plant is a favourite of mine, for several reasons:
    It is a cousin of Eichhornia crassipes, the Water-Hyacinth beloved in summertime ponds in the North and much-despised where the waterways are overrun in the South. The flowers of Pontederia are miniatures of Eichhornia’s, in more ways than one.
    Both species have a peculiar reproductive strategy: they have THREE genders (“trimorphism” or “tristyly”), a form of heterostyly or herkogamy, like to the “dimorphism” of Primula (where “Pin” flowers preferentially are fertilized by pollen from “Thrum” flowers and vice-versa).
    Anyway, a pandering politician by the name of Proxmire issued his “golden fleece awards” for what he claimed were risibly wasteful research grants, including one for “How Radishes Have Sex” (what an inappropriate image comes to mind!) The research in question had to do with the mechanism by which Rhaphanus could somehow select that ovule fertilization would favour outcrossing rather than self-pollination. This is important, because many economically important plants, like Malus (Apple), are pretty-much self-incompatible, while others, like Triticum (Wheat) are the opposite. For the latter, hybridization, though critically important to agriculture, is terribly complicated, expensive, slow and unreliable. Understanding the mechanisms and advantages of self-compatibility/incompatibility is of enormous economic significance, and radishes were the study subject. The system in Pontederiaceae is pretty damn interesting in this context!
    I really hope you all will research his subject a little; it’s a hoot!
    A very very interesting book: http://www.amazon.com/Wildflower-Genetics-British-Columbia-Northwest/dp/091984300X
    A place to start:

  10. Therese

    I have also photographed quite a few Pontederia cordatas in Quebec, North of Montreal, in the Laurentians. It may go up further North. The Location was North Wentworth, Quebec. So, expect it to grow much further North than your reference books say.

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