Petrie Island, located in the Ottawa River in Ontario, Canada, hosts a variety of unique plant species, particularly in its wetland and forested areas. Some notable plant species include:

1. Silver Maple (Acer saccharinum): Commonly found along the riverbanks, this tree thrives in wetland conditions.
2. Black Willow (Salix nigra): Another species associated with moist environments, it is often found in floodplain areas.
3. Eastern Cottonwood (Populus deltoides): Known for its rapid growth and tall stature, it is frequently found near waterways.
4. Wild Rice (Zizania aquatica): This aquatic grass is significant in wetlands and is an important food source for various wildlife.
5. Blue Flag Iris (Iris versicolor): A stunning flowering plant that grows in wet areas, contributing to the biodiversity of the island.

The island's diverse ecosystems support various other plant species, including shrubs and herbaceous plants that are adapted to the unique conditions of the area. The presence of these plants plays a vital role in the habitat for numerous bird and animal species as well.

For more detailed information about the flora on Petrie Island, you can refer to local environmental studies or conservation resources.