Update on Eradicating Algerian Sea Lavender: Month Two

It’s now two months since we began our trials of differing eradication methods for the Algerian sea lavender in the estuary at the mouth of the San Diego River.

Algerian sea lavender after receiving two months of solarization treatment

Solarization is not having the desired effect on the sea lavender. Perhaps we might have had better results had we begun the solarization later in the year, with longer, hotter days.

Scraping treatment after one month

Scraping treatment after two months 

Hand pulled treatment after one month

Hand pulled treatment after two months

One month ago, the growth of native flora in the plot where the Limonium ramosissimum had been hand-pulled had been about twice that of the plot that had been scraped. Now it looks like the natives in the scraped plot are catching up. Cover of natives in the hand-pulled plot is now about 35 percent, while native cover in the scraped plot is about 25 percent. Regrowth of the sea lavender in both the scraped and hand-pulled plots is about the same, with each plot having about 20 of the invasive plants.

            Considering that the results of treatment are virtually the same and how much more labor intensive hand pulling is than scraping, scraping might prove to be the favored method for removing the sea lavender. Stay tuned for updates on the Sea lavender.

Update on Eradicating Algerian Sea Lavender at the San Diego River Estuary

Yesterday was one month since we had started our trials of differing eradication methods for the Algerian sea lavender that is plaguing the estuary at the mouth of the San Diego River.

An Algerian sea lavender infested plot one month ago before treatment

The solarization has yet to show any effects upon the Limonium ramosissimum underneath the black plastic cover. This is unsurprising, given that most solarization projects leave the solarization material in place for at least two months.

Limonium treated with solarization one month after being covered with plastic

One month later there is an apparent difference between the area in which the sea lavender was scraped away and the area where we pulled the weed out by hand. The regrowth of the sea lavender is slightly greater in the area that was scraped. Neither the hand pulled plot nor the scraped plot, however, have a great deal of regrowth, with less than five percent of the plot area taken up by the sea lavender. The regrowth of the native flora is about twice as great in the area that was hand pulled. So far it looks like hand pulling is more successful in getting rid of the sea lavender and promoting growth by natives. Stay tuned for more updates on the Algerian sea lavender.

A plot that was scraped of limonium one month after treatment

A plot in which the limonium was hand pulled one month after treatment

Testing Methods For Eradicating Algerian Sea Lavender

More on the Algerian sea lavender project at Dog Beach. We’ve gotten the area of infestation mapped. Yesterday we started a project to see the effectiveness of differing eradication methods. We chose three methods: pulling the invasive plants out by hand, scraping them from the landscape with garden tools, and “solarization,” covering the plants with black plastic to deprive them of sunlight.

            Solarizing was the easiest method, just spreading the plastic out over the sea lavender. The other two methods took a lot more time, about 20 minutes to scrape a 6 x 6 plot and about twice as long to hand pull a plot of the same size.

About 75 percent cover by Algerian sea lavender

Nonnative and invasive species are big problem worldwide. They reduce species diversity and can affect crop yields. The continental United States has been invaded by more than 1,500 nonnative plants. Florida and California share the distinction of having the most nonnatives, with each state plagued with about 1,000 unwelcome taxa from around the world.

            As you can see from the photograph, the Algerian sea lavender really takes over. The plots we treated were about 75 percent covered with the unwelcome plant. It pushes out native pickleweed (Salicornia virginica), as well as rare and endangered species like grab lotus (Lotus nuttallianus). Stay tuned for updates on this project.

Algerian sea lavender removed by scraping

A plot being solarized to kill the Algerian sea lavender

Eradicating Algerian Sea Lavender in San Diego

I know I post a lot here about news stories, but I thought I would start including some of the things that I’m involved with on a personal level as well. Here goes.

I’ve volunteered with the San Diego River Park Foundation for a number of years now. And I’m really excited about this latest development, at least as far as my involvement with the organization goes. I’ve been working with a couple interns on an infestation of Algerian sea lavender (Limonium ramosissimum). This is an invasive of Mediterranean origin that plagues California estuaries from here in San Diego up the coast to San Francisco.

As an exotic or invasive, it hasn’t been around a very long time, so strategies for eliminating it have yet to be developed. Our first step has simply been to figure out exactly where it is. So far Winnie and Kayla, the two interns, have mapped out where the sea lavender is growing. They are also investigating strategies that have been used to eliminate similar exotics and exotic plants that are found in similar estuary environments.

Where the Algerian sea lavender has encroached in the estuary of Dog Beach at the mouth of the San Diego River