Invasion of the land-snatchers

Nonnative plants have taken root, and in some areas they reign supreme

NATURAL DEDICATION<br>Susan Mason checks on a work site in Lower Bidwell Park where Japanese privet (<i>Ligusticum japonicum</i>) has been successfully removed—not an easy task.

Susan Mason checks on a work site in Lower Bidwell Park where Japanese privet (Ligusticum japonicum) has been successfully removed—not an easy task.

Photo By Virginia Moran

Nonnative plant lists
The California Department of Food and Agriculture maintains lists of invasive plants ( Another great source is the California Invasive Plant Council The Natural Resources Conservation Service does a great job of consolidating all the various “lists” (

About the author
Environmental scientist Virginia Moran runs Ecological Outreach Services in Grass Valley. She holds degrees in field biology and botany, and she’s written for numerous publications over the past 20 years. She can be reached through

Sitting on the tailgate of my truck after a foothills hike, munching on a doughnut while looking out across the Sacramento Valley, I think of John Muir—and how he saw the landscape when he walked across the San Joaquin Valley in the late 1800s.

“The Great Central Plain … during the months of March, April, and May was one smooth continuous bed of honey-bloom, so marvelously rich that in walking from one end of it to the other, a distance of four hundred miles, your foot would press about a hundred flowers at every step. Mints, gilias, nemophilas, catillejas, and innumerable Compositae were so crowded together that had ninety nine percent of them been taken away, the plain would still have seemed to any but Californians extravagantly flowerey.

“The air was sweet with fragrance, the larks sang their blessed songs, rising on the wing as I advanced, then sinking out of sight in the polleny sod; while myriads of wild bees stirred the lower air with their monotonous hum—monotonous yet forever fresh and sweet as everyday sunshine."My heart aches thinking about it because the scene Muir describes is something I will never see. It is something none of us will ever see.

That’s because the native flowers, which are mostly made up of annuals, biennials and perennials, are on their way out. They’re going extinct across the state and possibly across the entire Western United States.

Here’s another early description of the California landscape, from Mary Austin’s 1903 book The Land of Little Rain:

“There is always a lupin [lupine] wash somewhere on a mesa trail. … In their season, which is after the gilias are at their best, and before the larkspurs are ripe for pollen gathering, every terminal whorl of the lupin sends up its blossom stalk, not holding any constant blue, but paling and purpling to guide the friendly bee to virginal honey sips … and of these there will be a million moving indescribably on the airy current that flows down the swale of the wash.”

Not anymore. There wasn’t a native lupine or any native plant to be seen in the wash I hiked through today. It’s covered with nonnative brome grasses (Bromus spp.), commonly called foxtails. And, as if to dig the point in further of how ecologically stunted things have gotten in the great state of California, the foxtails are stabbing my ankles through my socks.

But Austin’s “rainbow-colored hills” and the “soft web of bloom” are not what most of the diligent and determined American settlers saw when they got here, either. They saw grazing pasture, old-growth virgin timber, water, minerals, gold. They saw opportunity, money and prosperity for themselves, and this is pretty much all the human species has ever been about—itself.

If we have time or something strikes us at the right time, maybe we’ll put up a sign and declare some place special, but only after we get our other stuff done—our fields plowed, our houses and roads built, our dams up.

TAKING OVER<br>There are no young oaks coming in underneath the old ones in a former walnut orchard in Lower Bidwell Park, and the herbaceous layer—there used to be wildflowers here—has been completely devoured by nonnative brome grass (ripgut/foxtail), which is extremely flammable.

Photo By Virginia Moran

While Austin was waxing poetic about lupines, her neighbor was grazing the hell out of them while introducing some other plant in their place.

The definition of “native plant,” according to the California Native Plant Society, is a plant that was here prior to European contact. The definition goes on to state, “California’s native plants evolved here over a very long period, and are the plants which the first Californians knew and depended on for their livelihood. These plants have co-evolved with animals, fungi and microbes to form a complex network of relationships. They are the foundation of our native ecosystems, or natural communities.”

Current numbers show California has 5,862 native plant species, 2,387 endemic species, and at least 1,023 nonnative plant species. The number of nonnative species continues to grow.

Plants that grow nowhere else in the world but in California are called endemics. Of the 2,387 endemic plants, 1,955 are considered rare or endangered, are on a state watch list or lack essential information. Twenty-five California native plants are considered extinct.

A nonnative plant is a plant introduced from somewhere else and no one is really sure how it will act once it gets here—like an uninvited guest at a party. “OK, Mr. Giant Reed Grass (Arundo donax), are you going to behave yourself?” Answer: No. And once they’re established, you cannot simply ask these plants to leave. Giant reed grass, ripgut grass (Bromus diandrus) and star thistle (Centaurea spp.) aren’t going anywhere. Howdy neighbor.

The uninvited plants that decide not only to crash the ecological party but also to hit the neighbors’ places are called invasive nonnative plants, or “noxious plants.” Like any good guerrilla warrior, they invade and take over the native grasses, lupines, clovers and hundreds of other perfectly fine native wildflower species. It is not uncommon to be botanizing somewhere and find a cluster of native plants hunkered down, clinging to their existence on a steep slope, rocky outcrop or saturated wet spot just because this is where the nonnative weeds have not yet gone.

Some nonnative plants, too, have become “naturalized,” which is another way of saying they are here to stay, so get used to it. The line between nonnative and naturalized is a fuzzy one.

One woman’s native plant is another’s pain in the ass. One of the most annoying and locally invasive plants in the Sierra foothills is hedge parsley (Torilis arvensis). The seeds of this plant are like Velcro (apparently the seeds inspired Velcro’s creation). They get attached to anything and everything, including dogs, chairs and socks.

Hedge parsley is in the carrot family. I dropped my jaw (and weed wrench) when I found out hedge parsley is considered a rare plant in the United Kingdom. I wrote to them to come on over and get as much as they want. The response was that I am welcome to come over there and remove their invasive plants from California, like salal (Gaultheria shallon). I did not appreciate the snotty comment about our California poppy, which quite frankly is a far better nonnative plant for the U.K. than nasty hedge parsley is for us. Hurumph!

Then there is the not-so-small problem of “the thing that escaped from the nursery,” as in horticulture. Then all hell can break loose—periwinkle (Vinca) anyone? Many of the nonnative plants in California got their start at local nurseries (like the aggressive nonnative brooms Genista and Cytisus), and the battle still rages to get sales of these plants to stop. Nonnative plants can hybridize with native plants (London Planetree Platanus Xacerifolia) hybridizes with our native Eastern sycamore (P. occidentalis). In some cases, nonnative plants then attract their nonnative animal friends—after all, they evolved together.

BUTTERFLY DOMAIN<br>The yerba santa (<i>Eriodictyon californicum</i>) is important to pollinators, including rare butterflies. As you can see, the landscape, covered with blando brome (<i>Bromus hordeaceus</i>), will not provide nectar like Yerba santa, which often gets wacked out from “clearing.”

Photo By Virginia Moran

The nonnative brome grasses and many of the other nonnative annual grasses are thought to have been introduced into California more than 120 years ago when cattle were brought into grasslands and meadows. Nonnative plants introduced from the Mediterranean regions do well in California in part because the climate is so similar and, in the case of nonnative plants, their natural competitors are missing in the new habitat. Native wildlife typically shun nonnative plants, preferring the ones they evolved with, again giving a competitive advantage to the interlopers.

Indeed, nonnative annual grasses are flourishing in California, and as a result the California landscape is being converted into more of a nonnative annual grassland flora. This means fewer wildflowers, which insects need for nectaring. Coupled with the recent paranoia about fire, important native shrubs for pollinators such as manzanita (Arctostaphylos sp.); coyote bush (Baccharis pilularis), which can literally be completely covered with bees; goldenbush (Ericameria spp.); and many other native shrubs are being extirpated by massive “thinning” projects (i.e. habitat destruction for “fire safety”).

What come back in many cases are nonnative plants. Many of these areas will burn anyway, and at what cost to the ecology?

Invasive plants cost the state of California not only ecologically, but also economically—about $33 billion a year. They take over desirable forage for livestock, severely affect wildlife populations that evolved with native plants, increase fire risk, and consume tons of water. Salt cedar or tamarisk (Tamarix), once planted for erosion control by public agencies, can consume up to 300 gallons of water a day. (Removing it can result in water showing up on the surface within a few days. This is how dramatically it affects native riparian ecosystems).

The relationship between native plants and wildlife is one that has evolved over thousands of years, and these relationships can be complex. The state Department of Fish and Game has even created a database called CWHR (California Wildlife Habitat Relationships).

Former program coordinator Monica Parisi (now an environmental scientist for the habitat conservation branch of the state Department of Fish and Game) explained the WHR model provides something called a “suitability value rating,” which is a measurement of habitat suitability. It is a baseline value from which changes to this habitat can be measured. The WHR model allows a researcher to compare two habitats—say, pre- and post-impact. It is predictive, which means you can ask it a question and get an answer that may help with managing native habitats.

Parisi pointed out the model is a kind of index that can be used to look at possible trends in a habitat from a change in the system. “But the onus is on the user to translate the model as far as assessing impacts for resource-management purposes,” Parisi said. She reports the model is used by professionals all over the state and the world and is free to download from the state Web site (

The anchor point for this model is native habitats comprised of native plants. These two things go together. Change them and you change wildlife species dynamics.

When native plants are replaced by nonnative ones, an animal species may be pushed against a kind of evolutionary wall—build a nest in the tumbleweed and call it good or go extinct. This was the observation I made while doing surveys one year in San Diego County. I observed a female California gnatcatcher that had built a nest in, of all things, nonnative tumbleweed (Salsola tragus). This species would normally nest in native California sagebrush (coastal sage scrub habitat), which was being wiped out.

World-renowned entomologist and butterfly specialist Dr. Art Shapiro of UC Davis points out that a lot of insect species already are making evolutionary lemonade out of lemons. Native insects utilize nonnative plants. The mylitta crescent (Phyciodes mylitta) is a common butterfly that has made the transition from native thistles to the European weedy ones (cirsium, carduus and silybum). One butterfly has earned a new common name from switching from native members of the carrot family to nonnative “anise,” otherwise known as fennel (Foeniculum vulgare), which can be a serious weed in California. The butterfly is now known as the anise swallowtail.

ARE WE IN EUROPE?<br>This is the typical look of California these days—at least inhabited California. Soft chess, ripgut, tumble mustard (<i>Sisymbrium </i>sp.) and Tree of Heaven (<i>Ailanthus altissisma</i>) fill the landscape. None are native to California.

Photo By Virginia Moran

Shapiro points out that a third of the butterfly species in the state have been recorded laying eggs or feeding on nonnative plants. When pushed to the brink of extinction, evolution may favor the organisms that would rather “switch than die.” Climate change will favor the spread of nonnative invasive plant species, so things are definitely not looking up for those species that are unable to make the switch.

Is it too late?

Dr. Tom Griggs, senior restoration ecologist with River Partners in Chico, points out that the human species may now have itself backed up against the wall. Unless we actively manage California landscapes to promote and maintain what ecologists call “ecosystem services,” hope will not spring eternal.

Ecosystem services are things we take for granted, like a healthy wetland system that cleans water, insects’ pollination of our crops and the not-so-minor contributions of plants, which produce oxygen and sequester carbon, an important role in light of climate change.

“It’s everyone’s responsibility to understand what’s going on out there. Let’s face it, invasion of exotics is overwhelming, so we are pushed into a situation of eradication versus control, and we may be at the point where all we can do is control it,” said Griggs. He was emphatic that the future of biodiversity now lies in the same species’ hands that screwed it up in the first place—the ultimate paradox.

Griggs and many other eco-optimists take this conviction to the ground, literally, by implementing ecological restoration projects.

Susan Mason, watershed coordinator for the Big Chico Creek Watershed Alliance and president of the board of Friends of Bidwell Park, started on a path that changed her life in 1999 when she decided to “do some volunteer work.”

Nearly 10 years later, Mason is a dedicated voice and champion of restoring native California habitats. She has something many biologists and ecologists don’t have anymore—faith. While many believe saving California’s landscape from nonnative plants is nearly hopeless (including this author), Mason continues to organize volunteers to “weed bash” and has much to show for it.

Nonnative invasive plants are being eliminated from Bidwell Park thanks to Mason and hundreds of volunteers. This means critical ecosystem functions are also being restored. These folks are not just building community with one another, but restoring ecological communities as well. This has to be the epitome of “community service.”

(A table of the 132 nonnative and invasive plant species is posted on the Friends of Bidwell Park Web site—www.friendsofbidwell—along with a progress report for each species.)

Mason’s knowledge of the park is that of two old friends, one of whom knows the ailments of the other in intimate detail. When she stares intently at one spot and gets quiet, she’s devising a solution.

Like everyone else contacted for this article, she agrees that educating the public about native plants and their ecology is now imperative. In spite of my cynicism, by the end of the day with Mason, I found myself feeling chastened by her determination, and I suddenly had a strong desire to grab a shovel and beat the crap out of patch of goatgrass (Aegilops triuncialis). Groups like Mason’s give long-time biologists like myself, who have seen things get only worse, hope—and hope is priceless.

NOTORIOUS NEW NEIGHBOR<br>The most infamous of nonnative invasives is the Himalayan Blackberry Rubus (actually native to western Europe, not the Himalayas). It was introduced to North America in the late 1800s as a cultivated crop.

Photo By Virginia Moran

Not too long ago, I was traveling up the coast and stopped by the road to stretch my legs. Across the street there was a sign about a small historic building. The town was trying to save it by raising $10,000. I turned from that sign back to the field by the road, a mess of nonnative weeds, and the whole thing struck me as a kind of pathetic commentary on the state of the modern human species.

Our native plants are as much a part of our state and national history as is any historic building. Preserving historic landscapes could in fact be a greater contribution than saving a building because, unlike a building, native plant landscapes sustain us and thousands of other species.

So why aren’t we preserving native plant landscapes as part of our history? What could be more patriotic? They were here before we were.

You hear the word “green” in every other TV ad, but one could argue we are leaving the green out of the green movement. Switching out a few light bulbs while remaining ignorant about our state’s ecology does not a green movement make. Very few people can even name one California native plant. Where I live, it is typical for people to remove much of their native vegetation and replace it with “landscaping.” They remove native plants and replace them with ornamentals, most of which are from Europe.

My reverie over, I get back into my truck and head home once again, feeling disappointment and sadness—the result of an intimate knowledge of nature. I know I am grieving, and so are many of my botanist and biologist friends. We are paying the penalty of knowing too much.

As Aldo Leopold said more than 55 years ago: “An ecologist must either harden his/her shell and make believe that the consequences of science are none of his/her business, or he/she must be the doctor who sees the marks of death in a community that believes itself well and does not want to be told otherwise.”

None of what is happening was unexpected. It was all foretold decades ago by Leopold, Paul Erhlich, Thomas Lovejoy, Norman Myers, Rachel Carson and so many more.

Treasure the precious wildflower, for it blooms no more.