Daisies, other undesirable plants crowd out those that belong here

Weeding out pretty pests

Posted: Friday, July 19, 2002

A rose is a rose in William Shakespeare's book, but here on the Kenai Peninsula, a daisy is a weed.

That is, according to the University of Alaska Fairbanks Cooperative Extension Service, currently on the lookout for noxious and invasive weeds.

An invasive weed is a plant, either native to an area or not, that has the ability to spread itself so rapidly it can completely take over, choking out desirable, native species of plants, according to Extension Service technician Janice Chumley of the Soldotna office.

The white daisy, which is seen in abundance particularly along roadways and driveways, is one such plant.

"The daisy is imported to Alaska," Chumley said. "And, it comes back every year, reproducing and moving everywhere, and eventually, it will completely take over an area."

She said several factors contribute to a weed's ability to be so prolific, including the fact that the natural food chain of an area does not include that imported species.

"Many introduced plant species are not going to be eaten by our wildlife," she said. "Left unchecked, the species can overtake plants that do have natural controls, including plants that local wildlife and insects feed on.

"They may reduce areas of moose browse, for instance," said Chumley. "These will then become areas moose avoid, and moose will be forced out.

"Invasive weeds also have a tendency to get a jump start on desired plants. In a garden, weeds usually come up before desired flowers and vegetable plants, taking away water and nutrients from the soil before desired plants have a chance."

Invasive weeds become "noxious weeds" when economics enter the picture, according to Tom Jahns, land resources district extension agent, who works closely with agricultural growers on the peninsula.

"Noxious weeds are weeds that create an economic hardship," he said. "They reduce crop production or require large costs to control them, or they may displace wildlife habitat."

Jahns said if a grower raises hay to be used or sold as animal feed and undesirable weeds enter the hay field, animals won't want to eat the weeds. If allowed to spread, the weeds may even take over the entire field, prohibiting hay from growing at all.

A weed that tops Chumley's list of undesirables is hawkweed.

"It can outcompete any species on the slope," she said, describing an instance where an orange variety of it spread in Homer and has completely taken over the Hickerson Memorial Cemetery. It also has a yellow variety.


Cooperative Extension Service technician Janice Chumley holds up a sample of narrow-leafed hawksbeard that sprouted up last year and will replace woody plants including willow by shading out the other species.

Photo by Phil Hermanek

"It's a very attractive plant and people want to plant it in their gardens," said Chumley. "Then, in about two or three years, it takes over."

Other invasive weeds becoming common on the peninsula, according to the Extension scientists, include hempnettle, Canada thistle, dock weed, Norwegian cinquefoil, equisidum (or horsetail), mustard seed and narrow-leafed hawksbeard.

These can be introduced by cars and trucks passing along roads, by people and animals carrying the seeds or in topsoil or seed brought in after a construction project.

Many of the noxious, invasive weeds spread via the flower's seeds, but "many also have rhizomes,"Jahns said.

Rhizomes are stems of the plant that grow underground, producing plant shoots above and roots below.

As an example, Jahns points to the daisy that can actually be a part of the daisy plant that appears right next to it, and the one next to that and so on.

"Another example of an invasive weed that reproduces by way of rhizomes is the yellow hawkweed," Chumley said.

Similar in appearance to the common dandelion, the yellow hawkweed "has fibrous roots with nodes that can each produce separate plants and can take over, eventually becoming a mono-culture."

The dandelion differs in that it has a single tap root and can be controlled by spraying herbicide directly on the plant.

"Spraying herbicides over a large area to control invasive weeds, however, means you will be spraying the remaining desirable plants along with the weeds," Chumley said.

Once invasive weeds take over an area, they can't be controlled. Agricultural land, range land and wildlife habitat are destroyed permanently.

"If people learn something about a plant before bringing it into an area, it's a lot better than finding out later, when it becomes a problem," she said. "Exclusionary measures are far easier than eradication."

She described the problem of noxious and invasive weeds as being a problem for home gardeners, landscapers and agricultural growers alike.

"When people have problems with weeds, we will help them out," she said.

In addition to advice, the Extension office on Kalifornsky Beach Road also offers full-color brochures identifying problem plants in Alaska and information of prevention and control measures.

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