Invasive Plant Species

Invasive species can have a dramatic impact on the environment, economy, and human health. Invasive plants can outcompete native plants because they have little to no natural predators to moderate their spread, often release poisons that inhibit growth of native plants, have vigorous reproduction strategies, and can disperse easily. Invasive plants can reduce biodiversity, degrade fish and wildlife habitats, alter water quality, disrupt natural erosion processes, distort soil chemistry, and can reduce recreational activities.

Reporting and early detection of these species can help minimize their spread and possibly eradicate species before they become new infestations. To help treat, control, and keep our garden city clean of invasive plants, please report and be aware of spreading any of the following invasive plants:

• Reed Canarygrass
• Ornamental Jewelweed
• White Sweetclover
• Orange Hawkweed
• Canada Thistle
• Bird Vetch
• Yellow Toadflax
• Oxeye Daisy
• Common Tansy
• Narrowleaf Hawksbeard

Note: invasiveness rank prioritizes non-native plant species in Alaska on a scale of 0-100 based on four subcategories of invasiveness: ecological impacts, biological characteristics and dispersal ability, distribution, and feasibility of control.

Other ways to help prevent the spread of invasive species:

• Checking tires and boots of invasive plant seeds before going on roads or trails
• Purchasing weed-free forage for animals
• Gardening with Alaska native plants
• Minimizing soil disturbance whenever possible

 

Left: Reed Canarygrass bloom.  Right:  Reed Canarygrass stem and leaf attachment.

Reed Canarygrass
(Phalaris arundinacea)
Invasiveness Rank: 83

Characteristics

• Roots have rhizomes (creep at ground)
• Leaves are broad, >1cm wide
• Leaves spread from stem at right angles
• Flower head is dense and hangs off the tips of grass

Habitat: margins of lakes, streams, and wetlands

Impact: overcrowding; steals water resources

 

Left: Ornamental Jewelweed flowers.  Right: Ornamental Jewelweed leaves.

Ornamental Jewelweed*
(Impatiens glandulifera)

Invasiveness Rank: 82

Characteristics

• Stem is hollow and has a purple/red tinge
• Leaves have serrated margins
• Leaves are arranged opposite/whorled
• Leaves are oblong to egg-shaped
• Flower is white, red, pink, or purple

Habitat: ornamental beds

Impact: river bank erosion; out-competition

 

Left: White Sweetclover flowers.  Right: White Sweetclover leaves and stem.

White Sweetclover
(Melilotus albus)

Invasiveness Rank: 81

Characteristics

• Leaves are compound with 3 leaflets
• Leaves have a toothed margin that extends two-thirds down leaf
• Flower is white and fragrant (vanilla)

Habitat: streams, fields, vacant lots, airports

Impact: overcrowd and hurt riparian habitats

 

Left: Orange Hawkweed flowers.  Right: Orange Hawkweed plant with leaves.

Orange Hawkweed*
(Hieracium aurantiacum)

Invasiveness Rank: 79

Characteristics

• Roots have rhizomes
• Leaves contain a basal rosette
• Stem is leafless with occasional exceptions
• Stem and leaves contain thick, black hairs
• Flower head is orange

Habitat: disturbed sites, alpine areas

Impact: forms dense monocultures

 

Left: Canada Thistle flowers.  Right: Canada Thistle plant growing in the ground.

Canada Thistle
(Cirsium arvense)

Invasiveness Rank: 76

Characteristics

• Roots have extensive creeping rhizomes
• Lobes of leaves are spiny/prickly
• Tops of leaves are hairless
• Bottom of leaves are hairless or hairy
• Flower head is narrow and purple-pink

Habitat: overgrazed pastures, roadsides

Impact: overcrowding, crop yield losses

 

Left: Bird Vetch flowers. Right. Close up of Bird Vetch leaves.

Bird Vetch*
(Vicia cracca)

Invasiveness Rank: 73

Characteristics

• Stem is non-winged and climbing/trailing
• Leaves contain 8-10 leaflets
• Leaves contain branched tendrils
• Flower head is dense with one-sided, blue-violet clusters of 20-50 flowers

Habitat: roadsides, trails, hay fields

Impact: steals sunlight, space, and moisture

 

Left: Yellow Toadflax flowers.  Right: Yellow Toadflax plant.

Yellow Toadflax
(Linaria vulgaris)

Invasiveness Rank: 69

Characteristics

• Leaves are linear to narrowly lance-shaped
• Leaves are a bluish-green color
• Flower head has many small, snapdragon-like flowers
• Flower head is yellow with orange throat

Habitat: roadsides, railroads, ditches, fields

Impact: overcrowding, poisonous to cattle

 

Left: Oxeye Daisy flowers.  Right: Oxeye Daisy plant.

Oxeye Daisy
(Leucanthemum vulgare)

Invasiveness Rank: 61

Characteristics

• Leaves are less than 10cm long
• Leaves are spoon-shaped
• Leaves are coarsely or irregularly toothed
• Flower heads have white ray florets
• Flower heads have yellow disc florets

Habitat: meadows, pastures, ornamental beds

Impact: soil erosion, overcrowding

 

Left: Common Tansy flowers.  Right: Common Tansy leaves.

Common Tansy
(Tanacetum vulgare)

Invasiveness Rank: 60

Characteristics

• Stem is woody with a purple-red tint
• Leaves are twice-divided into narrow toothed segments
• Leaves exude a strong odor when crushed
• Flower heads have many button-like flowers

Habitat: roadsides, streams, waste places

Impact: overcrowding, native displacement

 

Left: Narrowleaf Hawksbeard flowers.  Right: Close up of Narrowleaf Hawksbeard leaf.

Narrowleaf Hawksbeard
(Crepis tectorum)

Invasiveness Rank: 56

Characteristics

• Stem leaves are narrow and have extensions at the base that appear to clasp the stem
• Sepals at the base of the flower are hairy
• Flower heads are stalked (branched)
• Similar to dandelions from afar but taller

Habitat: roadsides, fencing, railroads

Impact: overcrowding, forms monocultures

 

*Uncommon species that have been found recently within the area, please report immediately. If found, take a clear photograph of the species, a description of where it was found, and the coordinates of where it was found, if possible. Report findings to the Natural Resources Department at [phone].