Yellow Flag Iris (Iris pseudacorus)

Yellow Flag Iris (Iris pseudacorus)


Yellow Flag Iris grows in wet areas such as ditches, wetlands and around streams and ponds. It is an aggressive invader that forms dense thickets that prevent the growth of native plants. Infestations can impact amphibians, birds, and other wetland wildlife. Wetland plants are especially difficult to eradicate once established. Prevention is the only weapon we have in this fight!


Yellow Flag Iris originated in Europe, Western Asia, and Northwest Africa. It was introduced to North America in the early 1900s as an ornamental garden flower. It has since spread throughout Canada and the U.S. It can be found in several ponds and streams across Prince Edward Island.


Positively identifying Yellow Flag Iris can be difficult, especially when it is not in bloom. Here are some distinguishing features to look for:

  • ¬†Very robust iris, more so than native iris species
  • Leaves are sword-shaped, 0.5-1.5m long, 1-3cm wide, and have a raised ridge in the middle of the leaf
  • Large yellow flower with 3 petals facing up and 3 petals hanging down
  • Brown-purple stripes on petals
  • Blooms June to August
  • Flowers yield seed pods that resemble small, green, bananas
  • Forms large clumps
  • Extensive root system

PEIISC factsheet on Yellow Flag Iris

PEIISC factsheet on Managing Yellow Flag Iris

Yellow Flag Iris is considered a priority species for the PEI Invasive Species Spotters Network.  If you see this plant, please report your sighting.