INVASIVE PLANT CONTROL

Working to restore habitats in San Elijo Ecological Reserve and Carlsbad Hydrologic Unit.

Conservancy staff members work in conjunction with County of San Diego Parks and Recreation to control invasive plants in San Elijo Lagoon Ecological Reserve. This important work is funded by several restoration partners.

Staff continually monitor invasive plant occurrences, coordinate treatment and removal of invasive plants, and conduct re-vegetation efforts using native plants from local sources. Of particular concern on reserve lands are purple loosestrife (Lythrum salicaria), perennial pepperweed (Lepidium latifolium), and giant reed (Arundo donax).

The Conservancy is indebted to its docents and other frequent visitors of the reserve, who keep us informed about new infestations of these and other invasive plants.

Since 2004, San Elijo Lagoon Conservancy has administered a regional invasive species control program on behalf of Carlsbad Watershed Network (CWN). The CWN is a consortium of nine non-governmental organizations, seven cities in north-coastal San Diego County, County of San Diego, and more than 10 other governmental agencies and academia working to restore Carlsbad Hydrologic Unit (CHU).

The CHU includes the watersheds of the following waterbodies: Loma Alta, Buena Vista, Agua Hedionda, Encinas, San Marcos, Cottonwood, and Escondido Creeks. These watersheds drain into the Pacific Ocean. Restoration efforts focus on controlling the most threatening invasive plant species, listed below. Landowners with invasive plant species on their property are contacted, and written permission is obtained to access the property and initiate eradication of the invasive plant of concern. There are no costs or fees to the property owner associated with this project.

The targeted plants are treated by applying herbicide to the plant. Fully licensed and insured professionals carry out the applications. Once the plants are dead, the remaining biomass is reduced on the site if possible. This reduces the chances of infestation by other invasive plants. Extra care is taken to avoid impacting native vegetation during the biomass reduction process. If site conditions are appropriate, native plants are planted within the treatment area with the goal of restoring habitat function.

The priority invasive non-native plant species we focus on include:

• Giant reed (Arundo donax)
• Pampas grass (Cortaderia selloana)
• Perennial pepperweed (Lepidium latifolium)
• Tamarisk (Tamarix ramosissima)
• Mexican fan palm (Washingtonia robusta)
• Canary Island date palm (Phoenix canariensis)

These plants do extensive damage to private property and natural resources. They contribute to flood damage, increase risks associated with fire, and degrade native habitat. They also host rats and snakes. These plants spread aggressively, often onto neighboring properties, making them difficult to control. 

Before and after arundo removal and native vegetation regrowth along a stretch of Escondido Creek
(Photo: SELC Archives)

Re-vegetation with natives
Re-vegetating the area with native shrubs and trees reduces the risk of re-infestation, and improves habitat for native species. In riparian, or streamside habitat, native vegetation ultimately improves the quality of water entering the lagoons of the CHU, including San Elijo Lagoon. The program was initially funded by a Watershed Protection grant from the State Water Resources Control Board. With that initial funding we treated 279 acres of invasive non-native plants throughout the CHU and identified an additional 290 acres of invasive plants to be treated with other funds. 

The continuation of the invasive species control program is essential to maintaining and improving the ecologic health of the CHU. In 2006, the Wildlife Conservation Board granted an additional $1.5 million to the CWN for the continuation of the CHU invasive species control program. The Conservancy has also received funding from SANDAG’s Transnet EMP funds for invasive species control within the CHU. 

Our funding partners with the invasive species control program are:

• California Coastal Conservancy–Southern California Wetlands Recovery Project
• The Wildlife Conservation Board
• The California Regional Water Quality Control Board
• San Diego Association of Governments–Environmental Mitigation Program
• United States Fish & Wildlife Service

For this reason, the service imposes no cost on landowners to treat invasives on their properties. If you know of high-priority invasives (listed above) on your property, please contact our Land Management Staff for consultation (see contact in next column).