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Removing Invasive Species

Invasive species can outcompete native species and hurt local ecosystems. The Conservation Program removes invasive plants on Stanford lands, especially in sensitive habitats, to protect Stanford's biodiverse native ecosystems. You can help protect threatened species, reduce fire risk, and improve native biodiversity by joining us for a volunteer weeding day!

Sadly, Stanford has a lot of invasive species. This list describes some of the most notorious invaders on Stanford lands, but there are many others:

Taeniatherum caput-medusae

Also known as: medusahead, medusahead grass

Identifying it: Medusahead is a thin grass with long, spiky heads that stays green after most other grasses have browned.

Why it's a problem: Medusahead creates a dense litter layer that's difficult for native grasses and other plants to break through. It increases summer fire risk and is largely unappetizing to native herbivores.


Brassica nigra

Also known as: wild mustard, black mustard

Identifying it: Wild mustard has clusters of tiny yellow flowers on top of long stalks (sometimes up to eight feet tall!) It commonly grows along roads and in open grassland areas.

Why it's a problem: Mustard's explosive seedpod bursting, chemical (allelopathic) exclusion of native plants, and increased fire risk for some California biomes makes it one of the worst invasives the Conservation Program fights. We've made dramatic progress removing it over the last few years, in particular inside Gerona Gate (the right side of the start of the Dish trail).

Cytisus scoparius

Also known as: scotch broom, common broom

Identifying it: Woody shrub with bright yellow flowers

Why it's a problem: Scotch broom can quickly crowd out native species and increase fire risk.

Vinca major

Also known as: periwinkle, big periwinkle, greater periwinkle

Identifying it: Vinca is a dark green vine with purple-blue flowers about the diameter of a golf ball. It makes itself at home in shady, damper areas, like the riparian zones around Stanford's creeks.

Why it's a problem: Vinca's vines form a dense mat which allows it to take over an area and block other plants from growing.

Carduus pycnocephalus

Also known as: Italian thistle

Identifying it: Italian thistle has purple flowers and broader, spiky leaves. It is one of the most common invasive thistles.

Why it's a problem: Italian thistle can grow densely and exclude native plants, especially in grassland ecosystems, oak savannas, chaparral, or along disturbed margins. It can worsen wildfire risk in spreading grassland fires into tree canopies.

Centaurea calcitrapa

Also known as: purple starthistle

Identifying it: Spiky green leaves and purple flowers surrounded by 'starlike' spikes.

Why it's a problem: Purple starthistle can quickly grow as tall as a person and choke out native plants.

Dittrichia graveolens

Also known as: stinkwort, stinking fleabane

Identifying it: Dittrichia can look almost Christmas tree-shaped, with wiry, light green stalks growing up to a couple feet tall. It has small, pungent yellow flowers that resemble daisies.

Why it's a problem: Dittrichia's tens of thousands of wind-borne seeds and lack of appeal to grazing animals make it difficult to control. It has spread rapidly across California in just a few decades, and continues to spread today.

For more information about these invasive plants or others, please visit the California Invasive Plant Council webpage. For information about Stanford-specific removal efforts, please contact us!

Photo Sources

Cytisus Scoparius: Danny S., Wikimedia Creative Commons
Centaurea calcitrapa: Philmarin, Wikimedia Creative Commons
Vinca major: Forest and Kim Starr, Flickr Creative Commons

All other photos are creative commons photos with no attribution required or belong to the Stanford Conservation Program.