There are 657 species of plants on Haida Gwaii, almost 23% are introduced.
This does not include 361 moss and 160 liverwort species and many fungi and lichens.

Many plants were introduced for and remain decorative in our gardens or provide feed for livestock, but some are invading and overwhelming the native species. 

Some plants, like the yellowflag iris got themselves to Haida Gwaii. These plants were first found on the beaches of Luxana Bay and Frederick Island where they had floated from the south.
This iris is big concern in the Cowichan River estuary where it flourishes and excludes native species.

Many of the introduced plant species are restricted to roadsides or other disturbed areas but some are very invasive or aggressive and can move into sensitive ecosystems displacing native species.
Knotweed is one such species and can displace native species that have traditionally been used for Haida cultural purposes.

Knotweed has a unique method of spreading itself. It likes to grow on stream edges, where the roots break off and float away to re-establish itself downstream.
This may be a good for the plant but can add siltation to streams in quantities that cause serious problems for spawning salmon (picture).

Like the introduced Sitka black-tailed deer many plants have become a part of the Island lifestyle and management plans need to consider this social aspect. It is another need to monitor the impacts and perhaps conduct some control in order to maintain native ecosystems.