Seeds of destruction: Group works to clear invasive plants


These trees in San Elijo Lagoon are dying, and possibly being treated as an invasive species by the San Elijo Lagoon Conservancy. (Photo by Scott Allison)

Christopher Earley

Unbeknownst to many North County residents, they are living the midst of a battleground. But it’s not a traditional battle. And the enemies are a list of invasive plant species.

To the untrained eye, many of these plants may appear to be beautiful, lush parts of the landscape. But according to scientists such as Doug Gibson, they’re the root of a host of issues.

Gibson, principal scientist at the San Elijo Lagoon Conservancy, explained that these plants can house pests, cause changes in the hydraulic function of the soil and even increase fire danger.

Three of the worst offenders include the Arundo, or giant reed, pampas grass and castor bean. Similar to bamboo, the giant reed has been known to choke native plants and streams, causing flooding. Pampas grass, which was originally imported from South America as an ornamental plant, is especially dangerous because its plumes release loose seeds that scatter in the wind. Castor bean is a very aggressive plant, and like the giant reed, it can outgrow and eliminate native plants. Other invasive species include eucalyptus and palm trees.

While the giant reed and pampas grass can be purchased at some local nurseries, the conservancy and other groups encourage residents to avoid buying them, and to ask nurseries not to carry them.

According to Wally Kearns at San Diego’s Evergreen Nursery, they only carry the dwarf version of the pampas grass, which is sterile. Kearns said that they stopped carrying the fertile version not necessarily from pressure not to, but because of its invasive nature inside the nursery.

But the San Elijo Conservancy, which collaborates with the Carlsbad Watershed Network, has begun programs to control the invasives and restore areas in the Carlsbad Hydrologic Unit to their natural habitats. The watershed network includes seven cities in coastal North County, more than 10 governmental agencies and nine nongovernmental organizations.

The Carlsbad Hydrologic Unit encompasses more than 200 square miles in North County, and includes a number of watersheds.

Within the San Elijo Lagoon Ecological Reserve itself, the conservancy holds Community Habitat Restoration events on the third Saturday of each month, in which community volunteers help to remove invasive plants, and plant native species. In some cases, docents and visitors to the reserve keep the conservancy informed of new infestations, which are then targeted at these events.

“We’ve spent upwards of almost five and a half million dollars and we’ve restored something like 49 miles of streams, and approaching a thousand acres of habitat,” Gibson said. “So it’s really been a very big program of ours, and it’s all to better the community. And what we’re doing is saving the cities a lot of money in the long run because once they involve their sub-area plans for the habitat conservation areas, they’re going to be on the hook to control invasive plants.”

And according to Mike Grim, who is the senior planner for the city of Carlsbad’s Habitat Management Plan, the conservancy has done a good job helping them save time and money. One success story includes an area near the Costco at 951 Palomar Airport Road, where a grove of pampas grass had completely taken over.

“They (the conservancy) removed all of that, and the water table rose so dramatically, and we have an endangered species living in there that wasn’t there before,” Grim said. “We have an excellent habitat out there now.”

During a detailed planning process, the conservancy maps out problem areas, then determines who owns the property. Permission letters are sent to owners, and at no cost to them, the staff get to work eliminating the invasives, a process that most often includes the use of herbicides. They are also careful to avoid doing such work during bird breeding season, which runs from mid-February to September.

Gibson said that the invasive plant control program, funded by grant money from Proposition 13, has been successful in slowing down the spread of invasives since its launch in 2003. He’s careful to point out, however, that complete eradication is unlikely. And while they do have to return to the same sites, they’re doing so less and less.

Christopher Earley is a San Diego freelance writer