Stinkwort could be your new best friend or worst weed
Stinkwort at the I-280 and Page Mill Road exit in Palo Alto.

The STINKWORT (Dittrichia graveolens) is your BEST FRIEND, depending on what side of the California grassland fence you are on. --Are you maintaining exotic grasses for hay and grazing or are you restoring native bunchgrasses and wildflowers?

Copyright © 2013, 2017 by Craig Dremann, The Reveg Edge, Box 361, Redwood City, CA 94064 (650) 325-7333

The Stinkwort was first noticed in California in Santa Clara County less than 30 years ago. The infestations on the San Francisco peninsula are mainly spreading along the roadsides, and in 2017, this new weed is not being eradicated by any road management agencies, like those of Towns, Cities, County road crews or Caltrans.

Now that this new weed has spread to infest more than half of California's counties, government agencies are starting to pay attention, especially since it is showing up in the Napa County vineyards and there are concerns that the plant might give an off-flavor to the wines.

Also there are concerns about the plant going into the rangelands of the State, and injuring stock. BLM on their web site has issued the following notice:

Warning! Touching stinkwort can cause dermatitis, itchy skin, or blistering. Grazers that eat this plant can produce tainted milk or meat. When the seeds are ingested by grazing animals they can cause inflammation of the small intestine, and can lead to pulpy kidney disease or sudden death.

Stinkwort is a California native tarweed mimic, in that it has sticky stems and grows and flowers in the summer, after the annual weed grasses have died for the year. The original tarweeds could be called "exotic grazing-animal antibodies" in that they interfere with exotic animal grazing in California, and did not allow the animals to graze the land to barren dust and desert.

After 1865, when the perennial native grasslands were largely grazed to dust during the two year drought (William H. Brewer's accounts), then the non-palatable plants like the tarweeds flourished in California between the 1870s to the 1920s.

Photos taken by Frederick Clements when he worked at Stanford at the Carnegie Institution in the 1920s show how densely the tarweed grew in California grasslands, and ranchers have worked diligently to exterminate the native tarweeds and the other summer-blooming native wilflowers from rangelands. Tarweeds were probably largely wiped out after the invention of herbicides in the 1950s, so by the 1970s were absent from most of California grasslands.

Now, a new exotic tarweed-mimic recently arrived, spreading quickly to fill the ecological niche left by the essentially extinct native tarweeds. Stinkwort has now put a spotlight on the last 200 years of grassland management in California.

When the original California native grassland was exterminated, it included many tarweed species and other summer-blooming members of the sunflower family like the Golden Aster, the Gumplants and many others.

The Europeans and Americans were hoping to cherry-pick the useful-to-humans-and-their-introduced-livestock exotic grass, filaree and exotic and invasive clover species that could replace the now extinct native bunchgrasses and wildflowers.

However, an ecological rule is--When you exterminate an entire native grassland ecosystem and converting it to an exotic plant biome, it is impossible to have fields of only the desirable wild oats and not expect the weedy exotics like medusa head grass, and yellow star thistle to follow. You cannot have the desirable filaree without the potential of having stinkwort, cheatgrass, or Italian thistles for example.

So, the battle begins for the empty tarweed ecological niche in California. If you are using the original native grasslands for planting exotic plants like European grape vineyards, or using bunchgrass lands that have been converted to exotic grasses for grazing or hay, expect to budget tens of millions of dollars to keep Stinkwort from filling in that now-empty tarweed ecological niche.

Stinkwort's almost magnetic attraction to the open tarweed niche, plus the seed pappus allowing it to blow in the wind, will help this plant to eventually become perhaps one of the most hated weeds in California or maybe in the West.

However, if your job includes Ecological Restoration of the native bunchgrasses and wildflower fields, then this new weed can become your teacher. Stinkwort can be used to indicate, wherever it grows, that you still have some more work to do on that spot of land, to fill in all of the proper native grassland ecological niches and puzzle pieces.

Updated August 28, 2017. Back to Craig Dremann's main Contents page.