InTrans / Sep 28, 2015

Animals abroad: Do plants count?

Go! Magazine

Sign in weedsposted on September 28, 2015

In the last article, “Animals abroad: The invasion of the species,” we defined “invasive” and took a look at what impacts invasive species have on humans and the environment.

Next up is another, although non-mammalian, type of invasive species—plants! What can be done? What are the impacts of letting them spread?

First, let’s answer the most obvious question: How do plants move? Well, invasive plants can be spread through a variety of ways. Some of the main culprits include the wind, birds, and water. Humans also can aid in the spread of invasive plants, whether it be through gardening or at construction sites.

As we learned from the other articles in this series, once invasives begin to spread they are difficult to manage. Now that we know how they spread, let’s look at where they are going.


“According to the Federal Highway Administration, roadside rights-of-way account for more than 10 million acres of land in the US” (US Fish and Wildlife Service). Roadways are becoming one of the most prominent pathways in which invasive plants are spread. Why? Well, roadway corridors are often long, linear habitats that are rarely managed.

Invasive plant species can create new hazards for the roadways. Let’s take a look at some of the possible effects.

Decreased visibility

Plant species, such as the Japanese knotweed, can grow around traffic signs and thus reduce visibility. Knotweed is dangerous and can actually damage concrete foundations, roads, pavements, and buildings with its strong root system and growth.

Japanese knotweed covering up a traffic sign
Japanese knotweed covering up a traffic sign.

Native country: This invasive weed can be found in 39 of the 50 states in the US, and is native to eastern Asia, Japan, China, and Korea. The most effective way to eradicate knotweed is through use of herbicide during the flowering stage.

Interesting facts: Surprisingly, this plant is edible. It is actually valued by some beekeepers for its nectar and yields a mild, tasty honey.

Increased fire hazard

Following a wildfire, sometimes invasive plants can be at an advantage and take over during the natural recovery period. Some invasive plants, such as drooping brome, can even increase the intensity of fire. These are very dangerous for fire managers. Drooping brome not only spreads rapidly after a fire has taken place, but also can increase the frequency and intensity of fires by leaving behind dry leaf matter called “detritus.” This acts as literal “fuel to the fire,” thus making it a very dangerous invasive plant to have in areas prone to wild fires.

Drooping brome in Nevada
Drooping brome in Nevada. Photo from Wikipedia.

Native country: Drooping brome is prevalent in the US along rangelands, pastures, prairies, and roadsides. The grass is originally native to Europe, southwestern Asia, and northern Africa.

Interesting facts: Drooping brome seeds can be spread by rodents and/or attach to animal fur. The plant produces 300 seeds per plant!


Many plants exist that people should never touch. One plant that persists on roadsides is called giant hogweed, which can have stems that are more than two meters high. The sap from the giant hogweed plant is phototoxic, which means that when it touches human skin and then is exposed to sunlight, it can cause severe skin inflammation. This poses problems to roadside managers trying to manage invasive plants. Anyone harvesting this plant should wear protective gear to protect their skin.

Giant hogweed
Giant hogweed. Photo from Wikipedia.

Native country: Although originally from central Asia, it is prevalent now in the northwestern and northeastern US.

Interesting facts: Giant hogweed was actually introduced on purpose because of its pretty flowering. One tactic to get rid of hogweed is to let pigs and cows eat it, because the toxins do not seem to harm them.

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By Jackie Nester, Go! Staff Writer

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