Unwelcome weed 'stinkwort' spreading quickly in California

 

Invasive weed stinkwort, Dittrichia graveolen, can spread rapidly on overgrazed land, river and stream banks and roadsides.

UC Cooperative Extension experts are advocating for aggressive control of invasive stinkwort to prevent it from becoming an established California weed, reported the Sacramento Bee. Joe DiTomaso, UCCE specialist in the Department of Plant Sciences at UC Davis, said he believes CalTrans will have to treat stinkwort as an invasive of high and unique concern if it has any hope of controlling its spread.

Stinkwort made its first California appearance in 1994, but remained quite rare until the mid-2000s, when it began spreading rapidly. Stinkwort is now found in 36 of the state's 58 counties, particularly along roadsides.

"If it gets a major foothold and produces millions and millions of seeds, then the seedlings will grow and they can form a carpet," DiTomaso said. "Then it would block light and prevent the growth of more desirable species – like native plants. It will out-compete them, and that is a concern."

Another troubling aspect is that the weed has been seen in vineyards, said John Roncoroni, UCCE advisor in Napa County, a weed science expert.

"I've seen it on the roadsides in Napa, and it's just encroaching into the vineyards at Napa Valley College," he said.