Sequoia and Kings Canyon National Parks Institute Fire Restrictions
Effective June 18, 2014, the parks are in Stage 1 fire restrictions, see link below for more information. These restrictions will remain in place until further notice. More »
Road Construction Delays Begin on Park Roads for 2014 Season
Expect occasional 15-minute to 1-hour delays at various locations in Sequoia and Kings Canyon National Parks beginning Monday, June 2, weekdays only, between 5 a.m.-3 p.m., including delays to/from the General Sherman Tree, Crystal Cave, and Grant Grove. More »
Vehicle Length Limits in Sequoia National Park (if Entering/Exiting Hwy 198)
Planning to see the "Big Trees" in Sequoia National Park? If you enter/exit via Hwy. 198, please pay close attention to vehicle length advisories for your safety and the safety of others. More »
You May Have Trouble Calling Us
We are experiencing technical problems receiving incoming phone calls. We apologize for the inconvenience. Please send us an email to SEKI_Interpretation@nps.gov or check the "More" link for trip-planning information. More »
Bull thistle (Cirsium vulgare) is a biennial thistle that grows sporadically at middle elevations of Sequoia and Kings Canyon National Parks. It is native to Europe, and has naturalized throughout many areas of North America; its presence has been recorded in all of the 48 lower states.
Bull thistle is one of the more frequently encountered non-native plants in the parks above 1,400 meters (4,500 feet). Its ability to thrive at higher elevations and in relatively undisturbed areas makes it a species of concern. Currently, it is most common in and around disturbed areas.
This robust thistle is distinctive because of its purple flowers and rough bristly leaves. It is most common in moist disturbed areas. The first year following germination, the plant appears as a rosette of rough, spiny leaves. During the subsequent year, the plant bolts and produces spiny heads of purple flowers that produce abundant seeds. Each plant can produce more than one head. The bell-shaped heads are commonly 3-4 centimeters (1.2-1.6 inches) in diameter. The plant dies after it has produced seeds in the second year.
Photo by Brother Alfred Brousseau, St. Mary's College.
There are native thistle species that could be confused with bull thistle. The surfaces of leaves on bull thistle are rough to the touch, while the surface of the native thistles that occur in Sequoia and Kings Canyon National Parks tend to be smooth. The stems of bull thistle have obvious spiny wings. The native species tend not to have such distinct wings along the stem.
Bull thistle reproduces entirely by seed. A healthy plant can produce up to 5,000 wind-dispersed seeds. The seeds, however, do not remain viable in soil for long periods.
The most extensive infestation of bull thistle in the parks appears to be in and around the Grant Grove area. There are also populations in some areas of the park wilderness. Sequoia & Kings Canyon Natural Resource Management personnel have been actively controlling populations of bull thistle in the Grant Grove area since 1999.
Did You Know?
The yellow star thistle is one of many invasive and damaging non-native plants threatening the parks. It quickly takes over areas, displacing native plants and the native animals that rely on them. Please avoid bringing seeds and non-native plant materials into the parks. More...