All weeds in California that are thorny or have stickers were brought by the Spanish when they first came here to set up their ranches. They came in the bales of hay brought on ships for livestock they were transporting.
In the 300+ years since, these invasive weeds have crowded out native grass and other small plants statewide. It's fairly rare for me to find native grasses in meadows and grassland areas when I'm out hiking or mountain biking.
