Invasive plants threaten The Preserve’s biodiversity and natural beauty. Left unchecked, they can take over a landscape and out-compete native species. Invasive plants are those species that are not native to an ecosystem, which once introduced, cause harm to native plant communities. The Conservancy’s top priority invasive species to remove are French broom (Genista monspessulana), poison hemlock (Conium maculata), invasive thistles, including milkthistle, yellow starthistle, and bull thistle (Carduus spp., Silybum sp., Circium spp.), and stinkwort (Dittrichia graveolens). These plants may require intervention and control measures to reduce their spread, mitigate their impact, and stave off the threat they pose to our native ecosystems. Invasive species require ongoing monitoring and treatment to ensure their eradication. Strategies to control these plants include hand removal, mowing, or herbicide application.
Timing of treatment and annual maintenance are imperative for reducing of invasive weed populations. It can take several years to deplete the seed bank of these species in the topsoil to control and, ideally, eradicate these persistent plants. A major goal of treatment is to remove weeds before they “go to seed”, or introduce a new year’s seed to the soil.
Invasive species removal is a key component of the Conservancy’s Grasslands Initiative. To support this, the Conservancy deployed its first-ever Field Crew in March 2019. The five-member team worked full-time for 20 weeks to address prioritized invasive species threats- notably French broom, poison hemlock, thistles, and yellow starthistle – in Conservancy-owned Wildlands. Read more about the seasonal field crew’s experience here .
The 2019 Field Crew Team, from left to right: Brett Williams Scott, Isidro Blanco, Austin Robinson, Ryen Wright, and Christopher Terry.
For Openlands management, the Conservancy works with individual homeowners to devise a targeted weed management plan to eradicate invasives on The Preserve. Standards for managing invasive weeds in the Homelands are outlined in our 2019 Weed Management Guidelines.