Photo courtesy Kenai National Wildlife Refuge Water smartweed (Polygonum amphibium) grows on the surface of Daniels Lake in Nikiski.

Photo courtesy Kenai National Wildlife Refuge Water smartweed (Polygonum amphibium) grows on the surface of Daniels Lake in Nikiski.

Refuge notebook: What puts the ‘smart’ in Water Smartweed?

  • By MARIAH MCINNIS
  • Thursday, August 11, 2016 6:27pm
  • News

It was a beautiful sunny day and we were well into surveying for the hybrid Elodea on Daniels Lake. The sun was beating down on us and I suddenly realized that it is indeed possible to get sunburn in Alaska. Elodea is an invasive waterweed and we were hoping that previous efforts to eradicate it were successful and that we would not be detecting any on our sampling rakes. After pulling up an array of native aquatic plants but no Elodea most of the day, we were confident that it wouldn’t be showing up anytime soon.

Being a Florida native, Alaska sunburns aren’t the only thing I’m not used to. There are many plants that I’m not used to seeing here on the peninsula. One of these plants is the water smartweed (Polygonum amphibium) which caught my eye as our boat rounded a corner. It’s pretty recognizable with its bright pink buds that shoot up on a stalk a few inches from the water’s surface. There were so many that this area of the lake appeared dotted with pink.

But this plant is more than just a pretty sight—it’s incredibly interesting and serves many different functions. Not only is it native to Alaska, but this plant is found almost everywhere across the U.S. except for my home state of Florida, Georgia, Alabama and, not surprisingly, Hawaii. It’s also native to Asia, Europe, and parts of Africa.

As you can tell from its extensive range, Polygonum is a large and variable genus of around 65-250 species, depending on how taxonomists classify it. Common names for this genus include knotweed, knotgrass, tear thumb, and of course, smartweed. The genus name is from the Greek word ‘poly’ for “many” and ‘gonu’ meaning “knee” or “joint” in reference to the swollen jointed stem.

More recently it has been split into more natural segregate genera with the smartweed belonging to Persicaria, along with 100 other Polygonum species with similar flower structures. The name ‘Persicaria’ means “little peach” in Latin, named for the resemblance of the leaves of many species in this genus to those of little peaches.

The perennial water smartweed commonly grows semi-submerged in shallow water. The oval or short-cylindrical spikes of pink flowers and the floating elliptic or oblong leaves distinguish it from the closely related marsh smartweed (Polygonum muhlenbergii). They are typically found in fresh, moderately acidic or mildly alkaline water. Although they enjoy shallow water, they can continue to grow with very little moisture.

Plants may have bisexual or unisexual flowers, with some plants bearing only male or only female flowers. There is also a terrestrial form of the smartweed which is quite different in general appearance to the aquatic version. This trait explains “amphibious” in the full species name P. amphibium.

The smartweed has a long history of being used by humans. Plains Native American tribes used the species as a food source while others used the roots, stems and leaves medicinally. Many species under Polygonum are also used in a variety of Chinese medicines as well. Some species are thought to have antibacterial and antifungal properties as well as being an antioxidant.

When I first heard the name smartweed I immediately was curious about what made the weed so ‘smart’. Funnily enough, it has nothing to do with intelligence. The name apparently comes from the original word “arsmart” for the use of the plant in medieval times to relieve itching and swelling of the human posterior. I didn’t see that coming!

Not only have humans used the smartweed as a food source but they are also an excellent food source for waterfowl, particularly game ducks, of which Alaska has plenty! The small, pink seeds are the main part of the plant that is usually consumed.

In more recent years, scientists in England have found that the water smartweeds growing in old gold mine tailings can accumulate trace amounts of gold into their tissues at levels significantly higher than expected from background levels. Some have suggested that the plant could be used as a bioassay of useful minerals or to clean up badly polluted sites. Polygonum amphibium, in particular, is a good accumulator of phosphorous and nitrogen.

After all my research I felt genuinely surprised—I would have never guessed that this pink-budded waterweed could prove to be such an interesting plant with such a rich history. Who knows, maybe we’ll be seeing the smartweed being used in the future to help mitigate the effects of pollution. Now that would be smart!

Mariah McInnis is a biological intern at Kenai National Wildlife Refuge. She recently graduated from Florida State University, majoring in Environmental Studies. Find more information at http://www.fws.gov/refuge/kenai/ or http://www.facebook.com/kenainationalwildliferefuge.

More in News

A woman stands with her sign held up during a rally in support of Medicaid and South Peninsula Hospital on Wednesday, June 18, 2025 in Homer, Alaska. (Chloe Pleznac/Homer News)
Homer residents rally in support of South Peninsula Hospital and Medicaid

The community gathered on Wednesday in opposition to health care cuts that threaten rural hospitals.

Hunter Kirby holds up the hatchery king salmon he bagged during the one-day youth fishery on the Ninilchik River on Wednesday, June 7, 2023 in Ninilchik, Alaska. Photo by Mike Booz
Ninilchik River closed to sport fishing

The closure is in effect from June 23 through July 15.

Señor Panchos in Soldotna, Alaska, is closed on Wednesday, June 4, 2025. (Jake Dye/Peninsula Clarion)
Soldotna restaurant owner remains in ICE custody; federal charges dropped

Francisco Rodriguez-Rincon was accused of being in the country illegally and falsely claiming citizenship on a driver’s license application.

Brent Johnson speaks during a meeting of the Kenai Peninsula Borough Assembly in Soldotna, Alaska, on Tuesday, April 1, 2025. (Jake Dye/Peninsula Clarion)
Borough to provide maximum funding for school district

The Kenai Peninsula Borough School District will receive less money from the state this year than it did last year.

Jake Dye/Peninsula Clarion
Pool manager and swim coach Will Hubler leads a treading water exercise at Kenai Central High School on Tuesday.
Pools, theaters, libraries in jeopardy as cuts loom

The district issued “notices of non-retention” to all its pool managers, library aides and theater technicians.

A sockeye salmon is pictured in Kenai, Alaska, on Tuesday, July 25, 2023. (Jake Dye/Peninsula Clarion)
Fishing slow on Russian River, improving on Kenai

Northern Kenai fishing report for Tuesday, June 17.

Josiah Kelly, right, appears for a superior court arraignment at the Kenai Courthouse in Kenai, Alaska, on Tuesday, Nov. 26, 2024. (Jake Dye/Peninsula Clarion)
Anchor Point man accepts plea deal for November shootings

Buildings operated by a local health clinic and an addiction recovery nonprofit were targeted.

A demonstrator holds up a sign during the “No Kings” protest on Saturday, June 14, 2025, at WKFL Park in Homer, Alaska. (Chloe Pleznac/Homer News)
Homer hits the streets to say ‘No Kings’

Around 700 gathered locally as part of a nationwide protest.

Brooklyn Coleman, right, staffs The Squeeze Squad lemonade stand during Lemonade Day in Soldotna, Alaska, on Saturday, June 14, 2025. (Jake Dye/Peninsula Clarion)
Kids learn business skills at annual Lemonade Day

Around 40 stands were strewn around Soldotna, Kenai, Nikiski and Sterling for the event.

Most Read