Starr Ranch Audubon Sanctuary Thistle Removal

Starr Ranch is an Audubon Sanctuary in Orange County. It’s a 4,000 acre preserve of what was once a 10,000 acre cattle ranch in the 1960s. In the late 1990s, the research staff surveyed the grasslands within the ranch and assessed that close to 20% was invaded by artichoke thistle, Cynara cardunculus. The lead researcher at Starr Ranch initiated an adaptive management strategy to eradicate the artichoke thistle. The goal for the project was not complete eradication of the plant but to keep cover within a range of 0-5% in grasslands.

The restoration practitioners decided that chemical control was not an option, and began multiple experiments testing different control treatments. Based on their results, they implemented two removal strategies (Brush cutting and surface tilling) based on the abundance of thistle. Areas that were cleared of artichoke thistle were replanted with coastal sage scrub species and native grassland species. Their target goal date for complete control of artichoke thistle is 2015; however this was initially 2010. While it has taken longer than they originally anticipated, they are very satisfied with their methods and results (see the link to the newspaper article on the website).

I find this project interesting because they opted to use very labor-intensive methods when on a small budget, when in contrast the Nature Reserve of Orange County and The Nature Conservancy were spending close to a quarter of a million of dollars on artichoke thistle control. However, the neighboring control efforts did not incorporate any plantings or seed addition. It seems like the pairing control with active plantings done at Starr Ranch seems to have resulted in greater success (higher native species recovery) than the neighboring control efforts. Was taking a non-chemical approach better? It’s hard to say given it’s taken the ranch longer than the neighboring agencies to see large scale reductions in thistle cover given that they were working with a smaller area. But, for the organization this project has definitely been successful thus far -- it’s reduced thistle cover without using chemical herbicides.

Image credit: field covered in artichoke thistle taken at Starr Ranch. The image comes from the Starr Ranch website

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