milk thistle (Silybum marianum) observed in Santa Clara County, US-CA, US
iNaturalist: fexcad
Invasive Species
Milk thistle spreads aggressively in disturbed soils and roadsides near your neighborhood, and if you spot its spiny rosettes in a garden or park, it can outcompete native wildflowers before you know it's taken hold.
Someone spotted and photographed milk thistle — a prickly, purple-flowered plant originally from the Mediterranean — in Santa Clara County, California, and the sighting was confirmed as accurate by the iNaturalist community. Milk thistle is a tough, fast-spreading plant that shows up in disturbed areas like roadsides, vacant lots, and the edges of gardens. While some people grow it for its seeds, which are used in herbal supplements, it's considered invasive in California and can crowd out local plants.
Key Findings
A research-grade (community-verified) observation of milk thistle was recorded in Santa Clara County, CA in 2026.
Milk thistle (Silybum marianum) is classified as an invasive species in California, spreading across disturbed and open habitats.
The observation contributes to citizen-science occurrence data, helping track the plant's distribution across the state.
chevron_right Technical Summary
A research-grade observation of milk thistle (Silybum marianum) was recorded in Santa Clara County, California. This confirms the presence of this well-known invasive Mediterranean herb in the region, contributing to citizen-science biodiversity tracking.
Abstract Preview
Research-grade observation of milk thistle in Santa Clara County, US-CA, US.
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Species Mentioned
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Silybum marianum is a species of thistle. It has various common names including milk thistle, blessed milkthistle, Marian thistle, Mary thistle, Saint Mary's thistle, Mediterranean milk thistle, variegated thistle and Scotch thistle. This species is an annual or biennial plant of the family Aster...