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Yellow
starthistle first appeared as an agricultural
pest in alfalfa fields. It spread along roadsides, where it had
access to abundant light.
About 80 years after its introduction, yellow starthistle
invaded grasslands that were used for grazing.
Yellow starthistle produces seed in
pods that have bristles
and barbs. The pods stick to clothes and animal fur, dispersing
the seed to new areas.
Long distance dispersal results from human activities. Yellow starthistle
can be distributed in contaminated hay and uncertified seed and
on vehicles, such as machinery used for road work.
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Introduction 
