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What are the worst weeds?

The Nature Conservancy's mission is protecting land through direct action. But simply buying land or creating a preserve is not enough to maintain the value of the land for future generations. Sources of stress can damage the land and reduce its biodiversity, quality, and beauty.

Some of the worst invasive plant species are those which alter normal ecological processes. For example, in some deserts fire is rare. Exotic annual grasses may form a flammable carpet that can spread fire easily, and as a result the frequency of fires increases. The native plants are soon killed, and the invasive species spread even further. As a result, what was once a biologically diverse desert may become a solid infestation of just a few invasive species.

What is the worst weed? It depends on where you live. If you live in one of the 48 contiguous states of the USA, indicate your location by clicking on the map below. View a nefarious weed that lives near you!

spurge spurge spurge loosestrife loosestrife loosestrife loosestrife loosestrife broom broom broom knapweed knapweed knapweed knapweed tamarisk tamarisk tamarisk privet privet privet schinus lespedeza lespedeza lespedeza lespedeza honeysuckle
Do you live somewhere else? You are not immune to invasive species. Here are some representative, nasty invasive species problems for a number of other areas where The Nature Conservancy works:

Alaska--relatively weed free (but still invaded by species such as Alliaria petiolata (garlic mustard), this state's most pernicious invasive species are introduced animals.

Hawai'i--this state is beset by a vast array of invasives.

Canada--Many parts of Canada are infested with Lythrum salicaria

Other countries--see our developing section on invasives from other regions of the globe.

If you want to see more pictures of weeds, we have a complete inventory of the photographs on our website posted for your easy viewing. Take a look!

Q &A clinic
The most frequently asked questions answered for your edification.
Ppt presentations
Here we have PowerPoint presentations on invasive species. Web slideshow versions are also on line if you do not want to download the PowerPoint files.
Economic impacts
It is difficult to put an accurate price tag on the costs of invasive species. Here are a few results from studies that have tried to do so.
Learn even more
People who talk about invasive species often present facts without citing their sources. Are you curious about our sources? Here they are for you!
How you can help
Steps you can take to help us protect our own wealth of native biodiversity.

Other site resources

Red Alerts!
Species which are either new to an area, or are showing alarming symptoms such as signs of signicant, new expansion.
Conservation stories
Read about how different people have had great successes dealing with invasive species.
Tool reviews
Read our reviews of hardware that are useful for those working in invasive species management.
About us
Information about the core staff of The Nature Conservancy's Global Invasive Species Team.
Contact information
How you can contact the core staff of The Nature Conservancy's Global Invasive Species Team.

Updated June 2007
©The Nature Conservancy, 2005