Integrated Weed Management
University of California
Integrated Weed Management


Medusahead (Taeniatherum caput-medusae (L.). Medusahead (Mh) has been invading California rangelands since 1950.  It is an annual grass that germinates and matures later than more desirable annual grasses.  There is a very distinct color difference during the growing season and dry portion of the year.  During the growing season, Mh is a grey green color that stays greener later in the season after all other annual grasses have developed seeds and are starting to senesce.  Once seed development begins, the awns are very long and wavy, giving the appearance that give Mh its common name – Medusa’s head.  During the dry season, Mh is a lighter yellow color than they other annual grasses, allowing you to see the patch effect across the landscape.

Mh is not as palatable to livestock as other annual species, and quickly develops a thatch layer of the previous year’s growth.  The thatch layer prevents other species from germinating and growing, further allowing Mh a competitive edge.  A monoculture of Mh is quickly established, degrading the biodiversity of plants and animals that previously existed.  The thatch layer also reduces the carrying capacity of the ranch.

Since it matures later than other annual grasses, prescribed burning is a management tool that has had success at controlling the plant, both by breaking up the thatch and by killing the current year’s seed crop.  Currently there are no herbicides that will selectively kill one grass and not another.  Therefore the option for controlling chemically is not as appealing.  There would also be an added cost of re-seeding the area that was sprayed.   Controlled grazing and mowing have been effective to different degrees.   Precise timing is needed to be successful for both programs.  There are no biological control agents at this time for Mh.

For more information and research papers about Mh control, please go here.

If you are ready to enter the Medusahead Decision Support Matrix, please click here to walk through the process and determine management practices that work best for your Mh patches.

Mh samples
Medusahead Seed heads at different stages of maturity.

Green Medusahead seed heads in the field.

Medusahead seed head still green while other forages turning brown in background.

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