This session will focus on how invasive plants are impacting native plants and plant communities. We will share success stories about invasive plant management leading to increased biodiversity.
SESSION CHAIRS Dr. Amanda C. Swanson, Jutta C. Burger
California Invasive Plant Council, Berkeley, CA, USA
Dr. Amanda C. Swanson
California Invasive Plant Council
Amanda’s interest in plants, and especially the interactions between native and invasive plants, began while hiking throughout California in her early 20s. In September 2017, she received a PhD from UC Riverside which was followed by a postdoctoral position at the University of Wyoming. She previously served as an environmental scientist and land manager of four Ecological Reserves in Orange County with the California Department of Fish and Wildlife, where she managed invasive species, conducted plant and wildlife surveys, and supported multiple restoration projects. Amanda joined the Cal-IPC staff in January 2024 after serving four years on the Cal-IPC Board of Directors. Outside of work, Amanda has many interests but most enjoys spending time outdoors, playing music, and making food with her husband and two young sons.
Jutta C. Burger
California Invasive Plant Council
Jutta Burger is an ecologist and the California Invasive Plant Council (Cal-IPC)’s Science Program Director, where she leads its conservation and science programs, including the invasive plant inventory, regional invasive plant management planning and best management practice development projects, and synthesis of research and experience involving invasive plants to support conservation-based land management. She received a BS at Washington State University, an MS at University of Nebraska, and a PhD from UC Riverside. Prior to joining Cal-IPC, Jutta worked as a land manager at the Irvine Ranch Conservancy in Orange County, CA.
30.1 Using WeedCUT to Improve Weed Management and IPM for Native Plant Restoration
Chris McDonald1, Jutta Burger2, Scott Oneto3, Tom Getts4
1University of California, Cooperative Extension, San Bernardino, CA, United States. 2California Invasive Plant Council, Berkeley, CA, United States. 3University of California, Cooperative Extension, Jackson, CA, United States. 4University of California, Cooperative Extension, Susanville, CA, United States
Description Weeds and invasive plants are one of the greatest threats to native plants. Invasive plants are also one of the few habitat stressors that are likely to degrade restored habitat, leading to long term management and maintenance. In addition, many land managers are using integrated pest management (IPM) practices to control invasive plants on their lands. The University of California IPM program worked with the California Invasive Plant Council (Cal-IPC) and a variety of partners to develop a new and free, online tool, WeedCUT. This online tool helps land managers increase their understanding of IPM and adopt IPM practices on their invasive plant and restoration projects in natural areas. Land managers from a variety of experience levels from early career to seasoned professionals can improve their management success with this tool. WeedCUT describes in detail over 50 management techniques often implemented in wildlands. Management techniques in WeedCUT run the gamut from non-chemical, to chemical, to biological control. The tool also details nine different application techniques to ensure users are safely and effectively controlling weeds and reducing non-target damage to native plants. WeedCUT’s most powerful feature is its decision support tool, which can be used to identify potential IPM strategies for over 200 invasive plant species or to filter IPM techniques by site characteristics and/or by plant characteristics. In this interactive session attendees will learn about the key features of WeedCUT and how to build an IPM plan to improve native plant habitat and effectively control weeds and invasive plants.
Presenter Bios
Chris McDonald
University of California, Cooperative Extension
Chris is the Natural Resource Advisor for the University of California Cooperative Extension covering southern, Southern California. His expertise is in managing plants in wildlands with an emphasis on managing difficult weeds using integrated pest management. He conducts research on vegetation management by reducing weed populations and restoring native plant populations. Chris has conducted research and outreach activities in the southwestern US for 20 years working in arid and semi-arid ecosystems.
30.2 CNPS Herbicide Policy: When Are Herbicides Essential and Not Essential?
Bill Neill
CNPS Los Angeles/Santa Monica Mountains Chapter, Los Angeles, CA, United States
Description In 1998, former California Native Plant Society (CNPS) President Jake Sigg authored a Fremontia article titled “The Role of Herbicides in Preserving Biodiversity”, claiming that synthetic herbicides have a long history of safe and economical use. He concluded: “It is misleading to say that herbicides should be used only as a last resort. On the scale of the larger landscape, we already passed the last resort stage.” Subsequent CNPS policy continued to regard herbicide use as a last-resort alternative. In 2023, Steve Schoenig reactivated the CNPS Invasive Species Committee, which proposed that CNPS policy should view herbicides as “sometimes essential” for controlling invasive plants. This revised policy was approved by the Chapter Council in September 2024. As an example of when herbicide may be regarded as essential, I will discuss different approaches to controlling pampasgrass (Cortaderia jubata) in different environments. A comparison of different approaches to any weed management challenge is made easier with the new WeedCUT website developed by Cal-IPC and UCANR. For example, in the case of Arundo, WeedCUT considers tarping practical for areas less than 0.01 acre or about 450 square feet, but no non-chemical method is recommended for areas larger than this. A review of WeedCUT advice confirms that effective control of perennial invasive plants over large areas typically requires herbicides. The CNPS herbicide policy should be cited to help local park administrators and city councils better understand the role of herbicides in protecting biodiversity.
Presenter Bios
Bill Neill
CNPS Los Angeles/Santa Monica Mountains Chapter
During 25 years of employment as a geologist and petroleum engineer (1975-1999), Bill Neill became interested in the problem of invasive species – first, feral donkeys (aka wild burros), then tamarisk/saltcedar from Eurasia that infests desert springs and riparian areas. In 1983 he obtained a California herbicide applicators license and, as a weekend avocation, organized volunteers to cut tamarisk trees and saplings with loppers and chainsaws, then apply herbicide to the stumps, mostly on BLM and TNC land. In 1999 he commercialized his avocation by becoming a professional herbicide applicator, and switched to controlling about 20 invasive wildland weeds in natural areas of coastal watersheds. Since 2019 he has served as co-president or solo president of Los Angeles/Santa Monica Mountains CNPS chapter.
30.3 Detection and Monitoring Using Online Open-Access Databases
Ron Vanderhoff
California Invasive Plant Council (Cal-IPC), Richmond, CA, United States. Calflora.org, Berkeley, CA, United States. CNPS Invasive Plant Committee and Orange County Plant Science Chair
Description Online databases like iNaturalist, Calflora and the Consortium of California Herbaria (CCH2) are important tools for early detections and occurrence monitoring. These databases and tools are now essential components in invasive plant detection as well as rare plant occurrences. We will discuss and highlight the ease of reporting and documenting important new detections as well as delimiting the range of known populations, reporting abundance data, phenology, etc. Using these databases we will also explore and show examples of data-mining large numbers of plant observations to identify and report important new occurrences and management priorities.
Presenter Bios
Ron Vanderhoff
California Invasive Plant Council
Ron Vanderhoff performs invasive species assessments and reviews for the California Invasive Plant Council (Cal-IPC). He is also a member of California Native Plant Society Invasive Committee, and the Chair of Calflora.org. Ron has long been engaged in the early detection, reporting, and prioritization of regional invasive plants and especially facilitating communication and collaboration among citizen scientists, land managers and agencies, and the research community.
30.4 Booms and Busts of Invasion: Leveraging Monitoring Data to Evaluate Impacts of Brassica tournefortii in a Desert Sand Dune Community
Dr. Clarissa S. Rodriguez1, Dr. Lynn Sweet2, Melanie Davis2, Scott Heacox2, Dr. Cameron Barrows2, Dr. Loralee Larios3
1University of California, San Diego, CA, United States. 2Center for Conservation Biology, Riverside, CA, United States. 3University of California, Riverside, CA, United States
Description Arid lands house a diversity of flora and fauna, and the sand dune habitats of the Coachella Valley are no exception. This sand dune flora diversity is highly sensitive to yearly precipitation and is at increasing risk of plant invasions. However, because the diversity in these communities is often observed over time and an invader’s abundance may also vary with rainfall, it can be difficult to track the impact of a plant invader. In this study, we analyzed a 17-year plant monitoring data set to evaluate the cyclical boom-bust dynamics of the invader Sahara mustard (Brassica tournefortii) in a stable sand dune community and linked these attributes to plant community dynamics. We identified that the frequency of Brassica booms and the magnitude of these booms led to changes in plant communities. We found that increasing the mean magnitude of an invader boom led to a decrease in the asynchrony of species within the community and to the stability of the overall plant community. The mean magnitude of Brassica booms also shifted the relationship between community synchrony and stability, where the negative relationship that occurs in uninvaded communities became shallower with increasing boom abundance. Our results suggest that the asynchrony in species abundances that often confers stability within arid communities is being lost with high invasion. Our research highlights the application of a new invasion regime framework to capture invader impacts in a temporally variable system to guide management and mitigate the impact of invasive species and conserve native plant diversity.
Presenter Bios
Dr. Loralee Larios
University of California, Riverside
As an ecologist and associate professor, Loralee Larios leads a research group that seeks to understand the mechanisms that contribute to plant diversity and how those might be impacted by plant invasions and environmental change to aide management and restoration.
30.5 A Regional Collaboration to Survey, Monitor, and Treat Nonnative Limonium Species to Manage and Protect Rare Plants in San Diego Bay Coastal Habitats
Jessie S. Vinje1, Carolyn Lieberman2, Emilie Luciani2
1SageVinje Biological, Escondido, CA, United States. 2United States Fish and Wildlife Service, Carlsbad, CA, United States.
Description European sea lavender (Limonium duriusculum) and Algerian sea lavender (L. ramosissimum) are two nonnative species recently introduced into California that threaten coastal ecosystems. These salt-tolerant plants produce abundant seed and form dense mats that displace native coastal vegetation, resulting in permanent loss of coastal habitats and rare plants, including salt marsh bird’s beak (Chloropyron maritimum subsp. maritimum). From 2021 to 2025, the San Diego Bay Nonnative Limonium Control Project, led by USFWS, SageVinje Biological, and multiple regional partners, surveyed approximately 1,400 acres around San Diego Bay, mapping 13.8 acres of nonnative Limonium spp. totaling over 417,000 plants within a collective 157 acres of infestation. We developed a project-specific ESRI Field Maps Application and trained project partners to use it, ensuring standardized data collection and streamlined mapping. To control Limonium spp., we implemented best management practices, including solarization/tarping, hand removal, targeted flame torching, and a combination of those treatments. While complete eradication of Limonium spp. is difficult and resource-intensive, our work proves that regionally-coordinated, data-driven control efforts are effective and over time, may lead to localized eradication of Limonium spp. and restoration of rare plant habitat.
Presenter Bios
Jessie S. Vinje
SageVinje Biological
Jessie Vinje is a biologist with 27 years’ experience in field biology, botany, and land management primarily in San Diego County. She started her career with the Bureau of Land Management in the Mojave Desert before moving on to private consulting and non-profit work focused on conservation, land management, and research in San Diego County. She has spent the last 14 years conducting monitoring, management, and research on rare plant taxa that occur primarily in western San Diego County and northern Baja California.
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The mission of the California Native Plant Society is to protect California’s native plants and their natural habitats, today and into the future, through science, education, stewardship, gardening, and advocacy.
DateSaturday, February 7
