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Persicaria amphibia

Also called Longroot Smartweed, Water Smartweed, Willow Grass

More About Persicaria amphibia

  • AKA Polygonum amphibium
  • Habitat includes shallow waters along lakes, ponds, ditches
  • Adaptable to short periods of drought
  • Long stems may creep, float or grow erect, before rooting at the stem nodes
  • Leaves can be lance-shaped or take various other shapes
  • Can grow in water depths up to 2.5 meters or less
  • Pink, spiky, flower clusters
  • Bloom Time: June to September

Interesting Notes:

Native to Ontario

"Persica" is a latin word meaning "peach" and "aria" means pertaining to, which is referring to the similarity of the leaves. 


30-125 cm


0-0 cm



Water Knotweed Growing and Maintenance Tips

Persicaria amphibia are adaptable to various levels of water, including the ability to survive short periods of drought. They are suitable for naturalizing in storm sewer ponds and runoff ditches where water availability is inconsistent. Both terrestrial and aquatic versions may take on very different appearances. 

Persicaria amphibia Characteristics

Full Sun
Full Sun
Partial Sun/Shade
Partial Sun/Shade
Deer Resistant
Deer Resistant
Native to Ontario
Native to Ontario
Bog or water garden
Bog or water garden

Soil Moisture

Moist to Average
Moist to Wet Soils
Wetland (Root submerged)

Foliage Color


Landscape uses