Idaho's Noxious Weeds – Yellow Starthistle

Home

Conservation planner

Conservation Funding Programs

Wildfire Management

Nutrient Management Plan

Pest Management

Pesticide Application Recordkeeping (PAR)

Animal Feeding Operations

Carbon Sequestration

Range Management

Farmstead

Organic Farming

Water

BMP/Conservation Practices

Reference

Idaho OnePlan recommends the website of the Idaho Weed Awareness Campaign as the best resource for up-to-date information about Idaho's noxious weeds, and their control.
Source for this page: Idaho's Noxious Weeds by Robert H. Callihan & Timothy W. Miller

BACKGROUND

Yellow starthistle (Centaurea solstitialis) originated in the Mediterranean area and Asia. It spreads exclusively by seed, which may lie dormant for as long as 10 years. It causes "chewing disease" and death in horses. Yellow Starthistle will grow wherever downy brome (cheatgrass) grows.

(Thumbnail images are linked to a larger photo)

DESCRIPTION

Yellow starthistle is a winter annualPlant that germinates, flowers, seeds, and dies during one growing season, maturing from 2 to 72 inches tall. A rosetteA circular, normally basal, clump of leaves of deeply lobed leaves up to 8 inches long forms after seed germination in the fall. Stem leaves up to 4 inches long develop in early spring, their blades forming fringelike extensions down the side of the stem. Yellow flower headsA group of flowers borne tightly together develop at the tips of branched stems from late spring until fall. Flower head bractsLeaflike structure at the base of flowers or leaves bear stiff, sharp thorns ¾ inch long. Seeds are tan with white and brown mottling, 1/8 inch long; both plumedA hairlike or featherlike structure, often on a seed and unplumed seeds are borne in each flower head. Plumed seeds are not highly windborne; unplumed seeds not at all.

DISTRIBUTION

Yellow starthistle is widely scattered throughout the U.S., but is a severe problem only in the West.

CONTROL

Three seed head weevils and 2 seed head flies have been good to excellent biological control agents in Idaho.

Agencies & Organizations | Contact Us | Site index | Site map | Search

This site and its content are ©2012 by The University of Idaho. You may not copy, transmit or reproduce any images, text or any other content without prior written permission.