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Sprawling patch on disturbed (mowed) oak grassland. There were no other plants in this field but for a few Shortpod Mustards (also invasive).

Southern Russian Thistle is number 23 on the list of “The Evil 25” invasive bully plants in the Santa Monica Mountains, https://www.nps.gov/samo/learn/management/invasive-plants.htm

The Center for Invasive Species Research, at UC Riverside, notes "Russian thistle is damaging as a seed contaminant, as a forage weed that may contain toxic levels of soluble oxalates and nitrates, and as an alternative host of several economically significant insect species. The mature plants break off at ground level, creating spiny, brittle, windblown tumbleweeds that fill drainage canals, catchments and swimming pools, and pile up against fences and dwellings, becoming eyesores, fire hazards, and foci for the accumulation of other windblown debris."
https://cisr.ucr.edu/russian_thistle.html