Invasive Plants

 What is an invasive plant?

An invasive plant is one that is harmful to native plants and ecosystems.  An exotic plant is a non-native plant that has been brought in by natural (birds, mammals, wind, water) or human (cars, trucks, shoes, garden ornamentals) means.  Not all exotic plants are invasive.  Some are benign.

Are all invasive plants equally harmful?

No.  There is a ranking system to determine how harmful an invasive plant can be.  The first question is: can the plant live in this new environment?  Many plants  that are highly invasive in a warmer climate, cannot survive in Alaska.  The plant is then rated on four more characteristics: ecological impact, biological characteristics and dispersal ability, distribution and feasibility of control.  The plant is then assigned an invasiveness ranking between 1 and 100.  Pineapple weed has a ranking of 32 which makes it of little concern.  It has not been observed in undisturbed natural areas and it doesn't compete well with native species..  It is easily pulled out and is a weed of farmyards and roadsides.  On the other hand, spotted knapweed has a rank of 86.  Research has shown that spotted knapweed can increase soil erosion leading to sediments in fish rearing streams, grow so densely that reduces native plant populations, is dispersed by wind so can travel far and fast, inhibits growth of other plants and seeds can remain viable in the soil for 8 years.

Plants ranked 80 or more are considered extremely Invasive.  They are ranked 70-79 are highly invasive, 60-69 moderately invasive 50-59 modestly invasive, 40-49 weakly invasive and less than 40 weakly invasive.  

What are the most invasive plants in Upper Lynn Canal?

Common Name


Invasiveness Ranking

Spotted Knapweed

Centaurea stoebe


Leafy Spurge

Euphorbia esula


Reed Canarygrass

Phalaris arundinacea


Ornamental Jewelweed

Impatiens glandulifera


White Sweetclover

Melilotus alba


Orange Hawkweed

Hieracium aurantiacum


Canada Thistle

Circium arvense


Perennial Sowthistle

Sonchus arvensis


Bird Vetch

Vicia cracca


Rugosa Rose

Rosa rugosa


Yellow Toadflax

Linaria vulgaris


Yellow Sweetclover

Melilotus officinalis


Herb Robert

Geranium robertianum


Foxtail Barley

Hordeum jubatum


Smooth Brome

Bromus inermis Leyss


Oxeye Daisy

Leucanthemum vulgare



What should I do if I find an invasive plant?

Report any high ranking invasive plants to the Takshanuk Watershed Council or The
Alaska Exotic Plants Information Clearinghouse ( AKEPIC )

NOTE: We have had reports of the possible presence of four highly invasive species.  Please let us know if you see any of them and exactly where you saw them.

Spotted Knapweed (86)
Leafy Spurge (84)
Himalayan Blackberry (77)
Japanese Knotweed (87)


Where can I get more information? click here or see below

See also Northern Lynn Canal Cooperative Weed Management Area








Click here to download    

                                                                                            Click here to download