UC Irvine

 Overview. Artichoke Thistle (Cynara cardunculus; CYCA), a deep-rooted perennial thistle, is an extremely problematic invader of disturbed grasslands in southern California. It has invaded large areas (over 4,000 acres) of the Nature Reserve of Orange County (NROC). The NROC, working with The Nature Conservancy (TNC), established a control program for CYCA involving direct application of herbicide to individual plants. Thousands of acres have been treated annually since 1994. We had three objectives of this project. First, we resurveyed areas initially surveyed in 1998 to assess the changes in areas that have been part of the control program. We particularly focused on changes in CYCA cover, and if it was associated with other aspects of NROC management (Brassica nigra; BRNI, Nassella pulchra; NAPU, native species richness). Secondly, we assessed how treated areas responded to the cessation of herbicide control for one year. Thirdly, we initiated a restoration project in eight areas with low native diversity. We detail the results of these efforts in this report, and include data collected as part of the accompanying CD.