Scotch thistle is the most common thistle species in New Zealand with spines on both the leaf surface and margins. Scotch thistle is a biennial weed, so it depends quite heavily on the establishment ...

Californian thistle is one of the most common thistle species in New Zealand. It is very troublesome in pastures because it is so difficult to control. Once a plant is established in pasture, it forms ...

Image via National Archives and Records Administration/ Wikimedia Commons (Public domain) While the Russian thistle's rampant spread through North America is perhaps the more well-recorded invasion, ...

February 24, 2025 – Yosemite National Park officials announce that it’s Invasive Species Awareness Week!

For more information visit Midwest Invasive Species Information Network (MISIN). Canada thistle forms extremely extensive root systems that need to be repeatedly damaged to keep them from growing back ...

Identifying features include: Like other thistles, bull thistle is armed with a great number of spines that can and will penetrate exposed skin. For more information visit the Midwest Invasive Species ...

“But some thistles, like Canada thistle, are perennials that spread through underground lateral roots as well as seed.” First ...

This thistle was placed on the endangered species list in 1987 due to severe threats from cattle grazing in its habitat on the Lincoln National Forest, home to 95 percent of its populations. After the ...

POPULATION TREND: The decline of this plant has been documented since 2000. Between that year and 2007, the total population plummeted from 35,000 to 24,000 individual plants.