Centaurea Species, Golden Star Thistle, St. Barnaby's Thistle, Yellow Cockspur, Yellow Starthistle

The bane of my childhood in Northern CA's Gold Country.

This plant is listed on the North Dakota invasive/troublesome list and this information is being distributed in a guide developed by the ...Read MoreND Weed Control Association and other agencies.

Plant Features
Winter annual or biennial, up to 3 feet tall
Single yellow flowers on the end of branches
Flower heads have long, straw-colored spine-like bracts arranged star-like
Small stiff hairs give plants a grayish look
Long taproot
Spreads by seed only
May germinate in fall as a rosette (dandelion-like) and resume growth in the following spring

Distribution
First introduced in North Dakota via contaminated grass seed. All known areas have been eradicated

Interesting Facts
If ingested, causes lethal neurological disorder in horses known as chewing disease
Actually a knapweed, not a thistle
Produces a toxin that inhibits other plant growth (allelopathic)
Most abundant noxious weed in California (infests over 14 million acres)

Yellow Starthistle, Golden Starthistle, Yellow Cockspur, St. Barnaby's Thistle Centaurea solstitialis is naturalized in Texas and other S...Read Moretates and is considered an invasive plant in Texas.

I can't believe this showed up on a gardening site. A particularly obnoxious weed with little ornamental value. A severe problem in much ...Read Moreof California, and hard to manage. Infests thousands of acres of rangeland; seems to suppress native vegetation. Seeds profusely; seeds will survive for years in the soil. The foliage grows very slow at first; while other plants are growing leaves, this one grows a long tap root straight down. By the the time most wildland foliage in my native foothills have browned-up in summer, the star thistle begins to bolt upward, gathering moisture from deep inside the soil. Toxic to horses. Nothing positive to say about this nasty plant.