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Nasty alien weeds a growing threat in populated corners of Alaska

  • Author: Rick Sinnott
  • Updated: May 31, 2016
  • Published July 10, 2012

When I arrived in Alaska in 1971, I stepped out of my green Volkswagen Beetle, knelt down, and pressed my palms and forehead to the ground. I was relieved at surviving 1,000 unpaved miles of the Alaska-Canada Highway but, more than that, I had fulfilled a lifelong goal, a pilgrimage to a personal Mecca. I wanted to be a wildlife biologist, and this was a land whose flora and fauna were little changed from prehistoric times.

Last summer, while I waited for my wife to finish admiring the fresh fruits and vegetables at the South Anchorage Farmer's Market, I took a good look at the ground beneath my feet. It bore no resemblance to the Alaska of my youth.

In an area little larger than the shadow of my pickup, I counted 10 invasive plants. I'm a wildlife biologist, not a botanist. But even I could identify dandelion, pineapple weed, foxtail barley, alsike clover, common timothy, yellow toadflax, narrowleaf hawksbeard, oxeye daisy, bird vetch, and common tansy.

The Last Frontier (for weeds)

Alaska's nickname, the Last Frontier, applies not just to development, or the lack thereof, but to weeds as well. Because the state is colder than most plants can tolerate, because of its relative isolation, paucity of roads, and limited areas suitable for grazing and farming, Alaska has lagged behind other states and countries in the race to replace native plants with more aggressive plants from Europe and Asia. But once started, the alien abduction of our state was fast and dirty.

Almost everyone is familiar with a few weedy species, with dandelions crowning the list. Most are unaware, however, that most invasive plant species have been introduced into Alaska since statehood. Other invasive species, already here in 1959, have grown much more widespread because nothing was done about them.

Eric Hulten documented and described Alaska's plants in his Flora of Alaska and Neighboring Territories: A Manual of the Vascular Plants, published in 1968. About half of Alaska's invasive plants have arrived since the publication of this monumental work.

According to the Early Detection and Distribution Mapping System website, Alaska has 223 invasive plant species, fewer than other states, especially California (582 species) and Florida (523 species). But we're catching up.

Ignorance is bliss

About eight years ago someone showed me a stalk of yellow flowers they had picked near my office that looked a lot like dandelions. But the plant had multiple yellow heads on a stiff stem, not a single bloom on a hollow, rubbery tube. It wasn't a dandelion. I shrugged and told the person I didn't recognize it either.

Several years later I realized the plant was narrowleaf hawksbeard, an invasive exotic plant. Then I noticed an invasive vine, bird vetch, covering the native flowers and shrubs along the Seward Highway in south Anchorage. Next I noticed rank growths of white sweetclover lining the streets. I was familiar with the plant from the Midwest, but had never seen it in Alaska.

Something insidious was happening. The city surrounded by wilderness was looking more and more like Los Anchorage, and despite my appreciation of natural ecosystems, I was as clueless as the next guy.

Although I had taken a class in identifying Alaska's plants at the University of Alaska Fairbanks in the early 1970s, I had forgotten most of what I had learned. I resolved to re-acquaint myself with Alaska's indigenous plants. A good place to start was in Anchorage's backyard, Chugach State Park.

Abducted by aliens

In 1986 a graduate student in the Department of Botany and Range Science at Brigham Young University completed a floristic study of Eklutna Valley, about 25 miles northeast of downtown Anchorage. Most of the valley is in Chugach State Park.

LuDean Marvin collected plants in the Eklutna Lake drainage from 1983 to 1985 and identified 372 species. Seventeen of those species were not native to Alaska: pineapple weed, common groundsel, common dandelion, shepherd's purse, pennycress, common mouse-ear chickweed, common chickweed, lamb's quarters, alsike clover, northern willow-herb, knotweed, common plantain, Iceland poppy, smooth-leaf crowfoot, Siberian wild rye, common timothy, and foxtail barley.

As a trained botanist who spent three summers in Eklutna Valley, there's no doubt Marvin was thorough. He probably didn't miss any introduced species, which often colonize disturbed ground, like the sand and gravel shoulders along Alaska's highways. I've found 8 exotic species in Eklutna Valley that Marvin couldn't have missed but didn't list: red clover, white clover, white sweetclover, yellow sweetclover, bird vetch, yellow toadflax, oxeye daisy, and narrowleaf hawksbeard. Although narrowleaf hawksbeard has spread onto the valley floor, all of these plants are most abundant along the road. That suggests that these species have colonized the Eklutna Valley since the mid-1980s.

Eklutna Valley is fortunate. I haven't found several highly invasive plants that are common in Anchorage – for example, orange hawkweed and European bird cherry – in the drainage. Marvin wasn't surprised that I'd found additional invasive species in the valley nearly 30 years after his research. Few residents live in Eklutna Valley, but increased traffic to the water treatment plant and campground area, and many more hikers and four-wheelers since the 1980s, have facilitated distribution of weedy seeds. Some weedy seeds hitch rides on tires and hiking boots.

Marvin was surprised that more weeds hadn't invaded the valley and suspected that elevation played a role. Certainly the paucity of roads and fewer disturbed areas, compared to Anchorage and the Mat-Su Valley, limits the spread of seeds.

At the opposite end of the spectrum, Anchorage, the state's transportation center, is the epicenter for the spread of invasive plants in Alaska. Anchorage leads the state with 162 reported species. The spread of exotic species is related to population and transportation networks. The heaviest infestations are in and around Alaska's largest towns, all serviced by road and ferry systems.

More remote areas are much less affected. But they aren't invulnerable. Other parts of Chugach State Park, closer to the Anchorage metropolitan area and major highways, have been hit much harder than Eklutna Valley.

Trading cottongrass for dandelions

When I arrived in Alaska, the roadside ditches were lined with cottongrass, a sedge topped with a tuft of white fluff. I'd never seen anything like it in the Lower 48 states, so cottongrass became one of the sights that made Alaska special. Now, when I drive around southcentral Alaska, I still see a disorderly rabble of white tufts in the ditches. But they are dandelions going to seed.

Dandelions are the quintessential invasive species, as ubiquitous outdoors as cockroaches in a Florida kitchen. They are also one of the first flowers to bloom in the spring. A field of dandelions beams like a classroom of happy yellow faces. Even the fragile seed heads are marvels of biological engineering. But most of the summer a ditch full of dandelions looks like a motley gathering of pale fleshy antennae.

As spring slides into summer the insurgents of one alien nation reinforce the next along our state highways. First dandelions, then white oxeye daisies, yellow hawksbeard, and bronze foxtail barley. Soon the robust spikes of white and yellow sweetclover will take over.

These days almost every plant one sees along the sides of the Glenn Highway between Anchorage and Wasilla is an invasive species. Tens of thousands of people drive the highway every day; most don't notice. They don't notice the rubbery stems of dandelions, the multiple yellow heads of hawksbeard, the head-high stands of sweetclover just now overshadowing the other roadside plants. When I drive the highway, I see millions of illegal aliens taking jobs from native wild flowers.

Ornamental moose

Every time I write a column on invasive species, a guy who works at the Alaska Division of Agriculture's Plant Materials Center sends me fan mail. Here's an example: "Dandilions [sic] aren't native to Alaska and neither are you or I. We all migrated here. A moose that eats a poisonous shrub probably has genes that the world could do without."

Here's another example: "Do you not recognize the cultural value of human's propensity for moving and culturing useful species (plants in particular) in new areas?"

Well, yes I do. I enjoy eating fruits and vegetables and smelling roses as much as the next fellow. But do you not recognize the cultural value of not turning Alaska's wild areas into a 586,412-square-mile vacant lot?

Many states are already spending millions of dollars to reduce or eradicate invasive plants that threaten livestock, agricultural crops, or wild areas. California spends $82 million every year for invasive plant control, monitoring, and outreach. Estimates of actual impacts, just in California, reach into the billions of dollars. Alaska will follow suit unless we slap some sense into some invasive plant apologists.

But it's not surprising that someone employed by the Alaska Division of Agriculture thinks the only "useful" species are those domesticated or broadcast by humans.

Ironically, it's the people who promote, sell, and cultivate domesticated plants who brought most of the invasive plants to Alaska. Farmers and other agricultural specialists tolerate low levels of weeds, which they often combat with pesticides. Of course, weeds that jump the fence are no longer their problem. Plant nurseries and gardeners import invasive weeds in the same pots as more desirable species, and some otherwise desirable flowers and ornamental plants turn out to be very invasive. Purple loosestrife and yellow toadflax have been sold in Alaska as ornamental plants, but their seeds also contaminate seed mixes.

Highways are a major vector for the spread of invasive species. Highway landscape engineers like to revegetate roadsides with plants that spread quickly to stabilize disturbed soil. Non-native plants that spread quickly are likely to become invasive. For example, white sweetclover is believed to have been brought to Alaska in imported forage or by roadside seeding projects. Reed canarygrass was still being used to revegetate roadsides in 2005.

While some invasive plants are used in folk medicines, eaten in a salad, or brewed as a tea, most were not moved to Alaska because they were "useful." They were weed seeds in grain or hay. They were a unique flower to plant in a garden to satisfy an aesthetic impulse or impress the neighbors.

Some invasive plants are inedible or even poisonous to native wildlife. Unlike the plant materials guy, I'd rather have ornamental moose than ornamental May Day trees.

Invasive is as invasive does

I guess it all depends on how one defines the term "invasive." You don't have to take my word for it. Experts with the Alaska Exotic Plants Information Clearinghouse (AKEPIC) at the University of Alaska Anchorage have ranked exotic plants by "invasiveness." In the simplest terms, they define "invasiveness" as the likelihood of a non-native species establishing itself in Alaska compounded by its adverse consequences to the natural environment.

Invasiveness is relative. Most of us have had some experience battling tenacious lawn weeds like dandelions. It's sobering to realize that AKEPIC considers dandelions and the three species of clover you're likely to find in a yard to be only modestly invasive. Chickweed, plantain, and pineapple weed, other scourges of local gardens and yards, are less invasive than dandelions.

Dandelions, clovers, and chickweeds are wimpy opponents compared to roadside weeds that have recently expanded their footholds in Alaska. According to AKEPIC, white sweetclover is one of about 20 plants that are considered extremely invasive in Alaska. Each white sweetclover plant is capable of producing up to 350,000 seeds. The plant contains coumarin, a toxic compound which presumably discourages foraging. Bird vetch is almost as bad; it's considered highly invasive by AKEPIC. Other common roadside weeds – yellow sweetclover, foxtail barley, oxeye daisy, yellow toadflax – are all more invasive than dandelions.

Invasive plants don't just remain meekly on roadsides. They spread into adjacent meadows and naturally disturbed areas like floodplains. For example, extensive infestations of white sweetclover have been found on Stikine, Tanana, and Matanuska river bars.

Some of Alaska's most invasive plants are aquatic species. These plants threaten to change the natural environment in ways roadside weeds can only dream of. I'll admit that my objection to dandelions is primarily aesthetic. But purple loosestrife and reed canarygrass can take over streams and wetland areas by forming dense stands that exclude and displace native plants and alter biogeochemical and hydrological processes.

No geese, no ducks, no terns, no swans

About a decade ago, some Alaskans started fighting back. Purple loosestrife, an invasive species long planted by local gardeners who didn't think it would spread, had jumped into Chester Creek, a small stream in midtown Anchorage that drains into Westchester Lagoon. The next step was the man-made lagoon itself. In 2005 a well-organized group of volunteers rooted the plants out of Chester Creek. But subsequent efforts have been necessary to eliminate the threat.

Michael Shephard, a plant ecologist with the U.S. Forest Service, expressed the threat of purple loosestrife in terms that most Alaskans can grasp. "This plant, if it were to get established in Potter Marsh, would absolutely cover the marsh," he said. "There would be no more geese, no ducks, no terns, no swans … and then it's just one hop away from the Kenai Peninsula" where purple loosestrife could damage salmon-spawning and rearing habitat that support world-class sport, commercial and personal use fisheries.

The best time to counterattack weedy aliens is when they first appear. Photos and other information on Alaska's invasive plants are on AKEPIC's website. Citizens Against Noxious Weeds Invading the North (CANWIN) is sponsoring Weed Smackdowns in several affected communities and is looking for volunteers.

Rick Sinnott is a former Alaska Department of Fish and Game wildlife biologist. The views expressed here are the writer's own and are not necessarily endorsed by Alaska Dispatch. Contact him at

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