Lunada Canyon gardening

I volunteer about once per month to look after Lunada Canyon.  This weekend I was inspired to spend about an hour cutting back on some Acacia cyclops (aka red-eyed wattle or coastal wattle) which is a native of Australia that is invasive in California due to prolific seed production and bird-dispersal of seeds.

In South Africa, they have used biological pest control to decrease the spread of this plant.  They report 90-100% seed damage when a seed-feeding weevil, Melanterius servulus, was unleashed on the Acacia population.(Biological control of an alien tree, Acacia cyclops, in South Africa: impact and dispersal of a seed-feeding weevil, Melanterius servulus, F.A.C. Impsona, V.C. Morana, J.H. Hoffmanna).  (The bad news is that the weevil spreads about 2 km per year.)

 As I started cutting back Acacia branches, I found Artemisia Californica (California sagebrush) and Heteromeles arbutifolia (Toyon) hidden under the outer branches.  Photo above shows Toyon in foreground and Acacia in background.

Along the way I pulled and roughly chopped  some Anise (Foeniculum vulgare).  Unless this has seeds, I like to mulch it in place.

 The Acacia had for the most part already gone to seed.  Above photo is one of the rare times I found remaining seed.  You can see why it's called red-eyed wattle.

 When I was done, the Sagebrush and Toyon could breath (above).

I left my pile (the fresh one at right) and alerted the PV Land Conservancy who have the capability to pick up large amounts of green trash.  There's clearly more work to be done.

There's a ton more of this plant around the peninsula.  Fortunately, there may be a biological pest control available.  From the abstract of the article mentioned earlier,

Several Australian Acacia species have become highly invasive in a number of ecologically sensitive areas of South Africa. Many have useful attributes that, to an extent, have hampered biocontrol efforts by restricting potential agents to those reducing seed production whilst not affecting vegetative growth. The outcome of the introduction of a seed-feeding weevil, Melanterius servulus, against Acacia cyclops in 1994, was assessed by investigating the plant’s reproductive phenology, as well as levels of damage caused by the beetles. The study provided essential information on host/agent interactions and, on the build up and spread of populations of the agent. Seed damage is commonly as high as 90% (exceptionally it reaches 100%), and dispersal rates of the beetles on average is almost 2 km per year. The consistently high levels of seed damage achieved hold promise for the future of the program, however, its ultimate success will be further enhanced through the integration of biological control with other manual clearing operations that are currently employed on a large scale in South Africa.

So, in other words, you can have your mature plants but slow their spread into new regions while you plot their demise on your own schedule.  Sounds good to me.