The Process

Weed Management & Habitat Restoration

Removing Invasive Weeds

This project, the removal of the most invasive weeds in the wetlands and replacement of those weeds with native plants, started in 2005 when we noticed that certain invasive weeds (8-10 species) were rapidly increasing.  These weeds included Harding Grass, Perennial Pepperweed, Star Thistle, Italian Thistle, Bull Thistle, Cardoon, Poison Hemlock, and Black Mustard.  In 2005 we clipped the seed heads off the Harding Grass to retard their expansion.  In December 2005 we wrote a weed management plan with a habitat restoration section and presented it to the City of Petaluma in January 2006.  Mechanical portions of the plan were approved in April 2006.  That summer we clipped Harding Grass seed heads and dug out nearly three hundred 4×4-foot bags of Italian Thistle, which represented about one third of the Italian Thistles in the park.  In November 2006 the chemical portion of our plan was approved.  By January 2007 we were using Roundup to remove the massive Italian Thistle population in Shollenberger.  We also sprayed the Harding Grass and removed Cardoon by a cut-and-paint technique.  A copy of our weed plan (nearly 300 pages) can be obtained on CD by calling 769-8961.

Planting Native SpeciesWe are growing native plants to replace the weeds we remove.  This is being done at a native plant nursery started by Dr. John Shribbs who teaches environmental science at Casa Grande High School (CASA) and is a co-author of our weed management plan.  The nursery is located at CASA and provided nearly 2000 plants between January and April of 2007.  Volunteers are needed to backup the student helpers at the nursery and to assist in the planting during the winter season.  If you can help at the nursery, call John at 769-8961.  Also, help is needed for mechanical removal of weeds between January and June.  Call Gerald at 763-3577 to help with the weed removal.

This weed removal and habitat restoration program will continue for several years at high Watering Plantingsintensity, and we are hopeful that a long-term, low-intensity removal will keep the most nonnative, invasive weeds out of our wetlands.  New invasive weeds are constantly appearing in California and will be treated with the “Early Detection, Rapid Response” approach encouraged by the California Dept. of Agriculture.

Financial donations for weed work are discussed on the Support the PWA page of this Web site.

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