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To outward appearances, orange hawkweed and northern pike may not have much in common. One's a plant; the other's a fish. But if you overlook the hawkweed's bright orange blossoms, you'll find an organism as voracious as the northern pike and every bit as tenacious.

"It takes over and excludes all other things growing in an area," said Janice Chumley, integrated pest management technician for the Alaska Cooperative Extension Service in Soldotna. "The flowers are lovely, but it becomes a monoculture."

Just as northern pike threaten the Kenai Peninsula's salmon stocks, invasive plants have the ability to displace native plants and change an entire habitat. Given their destructive nature, both are weeds and will be the focus of a free workshop from 9 a.m. to 3:30 p.m. May 1 at the Kenai River Center. The workshop will feature a weed and plant identification workshop, a presentation on reed canary grass and how it affects river systems, and biologists from the Alaska Department of Fish and Game who will talk about what pike could do to the Kenai River.

The workshop will also introduce those who attend to the Early Detection, Rapid Response program that's being developed in the Lower 48. Chumley said those who attend would be given an 800-number to call when they have a problem with invasive plants. And those who keep livestock will be able to learn where to purchase weed-free hay and animal forage.

"The folks that are going to speak are really dynamic passionate individuals," Chumley said. "They spent their own time and money to become weed warriors and they have really just an incredible story."

Invasive plants can push out native species in a variety of ways. One way is by blooming early. Chumley said even though most flowers have yet to bloom, dandelions have poked their heads out of the soil. If the insects pollinate the weeds before the native plants, the native plants don't get pollinated.

"Native plants here have a harder time because they develop in a colder climate, so they don't come out first," Chumley said. "If you look outside right now, dandelion's blooming (but) no native plants are blooming as yet."

If invasive species displaced willow trees, moose would have to go some place else to find food, she said. Invasive plants can also change erosion within watersheds and affect fire frequency, but not all non-native plants are invasive.

"When you stop to think, lawn isn't native and things like potatoes aren't native, but most people think of those as desirable," Chumley said. "The difference with an invasive species is they don't have any desirable qualities to them. They cause economic harm as well as environmental harm."

In addition to orange hawkweed and dandelions, Chumley said other examples of non-native invasive plants include sweet clover, hempnettle and Canada thistle. Sweet clover may sound lovely, but it has colonized gravel bars and river systems in Interior Alaska and has been found alongside the Anchor River and some roadsides. Underground rhizomes of the Canada thistle can grow up to 18 feet a year, Chumley said, and can produce plantlets along each nodule of growth.

"People that farm hay are having a lot of problem with some of the plants we think of as really not an issue," Chumley said. "Things like fox tail barley gets into animal feed. It has barbs that can cause abscesses in animals' mouths. That's a very common plant that's hard to get rid of once it's established."

People who attend the workshop will learn that seeds from invasive plants can hitchhike on clothing, vehicles and plants available at nurseries and grocery stores. Some wildflower mixes and birdseed can contain invasive plants as well, Chumley said.

Folks can come for the entire workshop or stay part of the day. Chumley encourages people to bring their own lunch, but said the cooperative extension service would try to have some refreshments there. The presentation on becoming a weed warrior will happen during lunch, she said, followed by a presentation on pike and reed canary grass.

"Reed canary grass was planted a long time as forage for animals," she said, adding that reed canary grass can be found in river systems. "It's escaped its boundaries and (wound) up changing fish spawning habitat."

Chumley said she hopes nursery owners and gardeners attend the workshop along with backpackers, fishermen and folks who own livestock.

"I think there's just a little something for everybody," she said.

Jessica Cejnar can be reached at jessica.cejnar@peninsulaclarion.com.