Invasive Exotic Plants

Invasive Exotic Plants are plants introduced to an area by humans
that may endanger native species or entire ecosystems.

They are also called “noxious weeds” or "alien" plants.

 

This patch of English ivy is smothering other plants by cutting off their access to sunlight.

NPS Exotic Plant Management Team

How Bad is the Problem?

They are a serious threat to wild lands
(other serious threats include habitat degradation and global warming).

Invasive plants can harm humans, cause crop damage, kill livestock, impede irrigation, as well as altering natural ecosystems.

They can affect fire ecology, water movement, soil erosion, native plants, and wildlife. The weeds do this by drying out wetlands, smothering native trees, poisoning animals, or causing other impacts.

 

The Exotic Plant Management Team treats some invasive plant species, like the Japanese knotweed pictured here, with careful and limited herbicide spraying.

NPS Exotic Plant Management Team

Prevention and Control

Prevention and early detection of invasive plants are the best and cheapest control methods. The more a weed has become established, the more costly and time-intensive it is to stop its spread. Control measures for invasive plants cost the National Park Service millions of dollars every year.

The NPS Exotic Plant Management Team treats invasive plants in Olympic and elsewhere after a complete site assessment and comprehensive park review. They use a control method that fits the particular species and location. The weeds may be controlled by manual pulling or cutting, by herbicides, or by other methods.

If you are starting any home weed removal projects, first contact your local County Noxious Weed Control Board for information and assistance.

 

Scot's broom, like this patch in flower,
can outcompete native plants if not controlled.

NPS Exotic Plant Management Team

Olympic's Worst Invasive Plants:

Scot’s Broom
Canada Thistle
Himalayan Blackberry
English Ivy
English Holly
Herb Robert
Japanese Knotweed

Want to help us here at Olympic
and elsewhere?

See Help Stop The Spread of Invasive Species

Report invasive plants in Olympic to the nearest visitor center or ranger station.

Want more information? See Weed Resources.