1. Insolent invaders

2. Slitherin' snakeheads

3. Got crabs?

4. Super swine

5. Too many blooms

6. Bogus buckthorn

7. Argentine ants

8. Weed of a 1,000 leaves

9. Weed-beater success story

This small field became a battleground against new weeds. Onionis photo courtesy G.F. Hrusa, Botany Laboratory, California Dept. of Food & Agriculture


"Wanted dead, not alive INVADING SPECIES: Restharrow, Onionis alopecuroides. Alias: With a name that weird, why bother?" Poster photo shows upright plants stand out above a field of brown grass on a hillside.


Heavily branched member of the legume family, known as highly invasive in northern Europe. First North American plants, the 0.7 acre group in the photo, found in 1998 near San Luis Obispo, California. Immediate eradication efforts began, with pulling and herbicides. Plant now under control.



Seeds could have spread downstream, causing wider outbreaks. In Europe, dense colonies outcompete native understory vegetation. Proves utility of an ounce of prevention: fast action staved off a major infestation.

More information




Sift through our weedy bibliography.




  The Why Files  

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