Of the nearly 200 non-native plant species in Sequoia and Kings Canyon National Parks, fewer than half appear to have significant impacts on park ecosystems. Many of these invasive plants (the foothill annual grasses in particular) are so well entrenched and widespread that it is not feasible to control them. However, many others are recent arrivals and will be relatively easy to remove in the near future.

In 2001, the Biological Resources Division of the U.S. Geological Survey published an extensive report detailing the characteristics of each non-native plant species known to exist in Sequoia and Kings Canyon National Parks. Each plant species was researched extensively and ranked according to its invasive ability, its current distribution in the parks, its ability to be controlled, and additional invasion characteristics. The findings of this report figure prominently in Sequoia and Kings Canyon National Parks' weed management program.

The plant species discussed in these pages are some of the most troublesome in Sequoia and Kings Canyon National Parks. Most of them are not well entrenched and can be removed if control efforts begin soon. Most of these species are the targets of current or future control efforts.

Prevention is by far the most effective means of controlling non-native plants. This fact is highlighted by the absence of yellow star thistle in these parks. While several individuals have been discovered, all were eradicated immediately and currently there are no known populations in the parks. Each year, millions of dollars are spent controlling this highly aggressive species in California. It is abundant in many areas adjacent to Sequoia and Kings Canyon National Parks. Early detection, costing almost nothing, has allowed the parks to avoid a major eradication effort.