In addition to rare natives, El Dorado County has seen the spread of invasive plant species. A study by Lyon et al (2010) examined barb goatgrass (Aegilops triuncialis) on and off serpentine soils in coast range and Sierra foothill (El Dorado County) locations. Serpentine soils are harsh, perhaps toxic, for many plants yet numerous species have evolved to tolerate those conditions (see video on serpentine featuring Dylan Burge below). Lyon et al found that barb goatgrass has an alarming ability to grow well on serpentine soils.
Stinkwort is another plant that is a serious problem in our county. It has been actively invading El Dorado County roadsides for 5 years and is now making its way into roadside meadows and pastures. Stinkwort is the plant growing up through cracks in highway 50 west of Placerville. Its pine-tree shape in summer is unmistakable as is the stench of its aromatic foliage. Neither deer nor livestock will eat it; new growth is only moderately palatable to goats.
For a brochure on stinkwort, click here.
Brooms, our most emblematic—and one of the most attractive—invaders were the subject of research at Blodgett (Stevens and Latimer 2015). Decreased snow and increased fire will likely result from global climate change and the researchers wondered whether these conditions will favor the expansion of brooms beyond their current lower elevational range into the higher mountains. They examined the survival and growth of Scotch (Cytisus scoparius) and Spanish (Spartium junceum) broom populations, planted from seed, with and without low intensity fire, under three snow levels. Both species germinated better following fire, and both species, but especially the more heat-loving Spanish broom, did much better under no snow than with any snow. They predict that reductions in the snowpack and increases in disturbances like fire can result in the expansion of lowland weeds to higher elevations.
Yellow Star-thistle is a common but serious problem in the county as well. For more, see https://www.edcgov.us/Government/Ag/UC_Davis__Pest_Notes_.aspx
Control of Invasives
Killing weeds before they flower and set seed is key to eradicating weed infestations.
Stinkwort: July is a good time to control stinkwort as the plant has not yet flowered. Stinkwort pulls easily from the ground (wear gloves!) and summer mowing can also knock back populations by preventing floweriing. Round-up and Garlon are effective herbicides for widespread populations according to Brownsey, Kyser, and DiTomaso, https://ucanr.edu/repositoryfiles/ca6702p110-102540.pdf
Broom:
Star Thistle: https://www.edcgov.us/Government/Ag/UC_Davis__Pest_Notes_.aspx
