Cortaderia is a genus of 20 species of ornamental grass, only one of which is grown commercially. This is peak flowering month in the garden for a couple of the lesser-known species of pampas grass. The first is Cortaderia araucana, which hails from Central/Southern Chile and Argentina. It’s much smaller than Cortaderia selloana and has performed beautifully for us in the garden.
Cortaderia egmontiana is also native to Chile and Argentina. In the two decades we’ve grown this, it has behaved beautifully, and is also slightly smaller than Cortaderia selloana and flowers over one month earlier.
Cortaderia selloana ranges from Bolivia south in to Brazil. It is the only species widely cultivated in the US. Two US states have put it on their invasive species list, but despite years of searching, we have yet to find a scientific paper documenting such tendencies. In California, Cortaderia selloana was grown for cut stems after the mid 1800s, and transported by open train across the state. As you can imagine, seed blew out of the train and it naturalized in adjacent open habitats. I’ve traveled these routes, and seen isolated clumps of pampas grass, but must have missed the areas where it chokes out native flora.
On its website, The California Department of Fish and Wildlife (CDFW) writes: Â “Cortaderia selloana is a quickly growing grass that forms massive clumps along roadsides, steep cliffs, river banks, and open areas that have been disturbed by human activities or natural disturbances.” In other words, it is well-adapted to disturbed habitats, compared to say, California natives. This is fascinating since “natives” are constantly touted to be much better adapted. If seeding along disturbed areas is a reason to ban a species, how about an effort to ban Cannabis sativa and put it on the invasive species list. There are hundreds of miles of Iowa roadsides densely carpeted with cannabis, a leftover from the hemp crops of earlier this century, when over 400,000 acres of it were grown during WWII. It’s much easier to pick on plants that don’t have an army of advocates.
CDFW goes on to write, “Invasive plants such as pampas grass displace native plants and create habitats that are lower in biodiversity. Furthermore, pampas grass has leaf blades that are highly undesirable as food or shelter to birds and other wildlife, and can actually cause physical harm to those animals, including humans, because the leaves are extremely sharp.” Really? Cactus, agaves, dasylirion, nolina, etc. all have equally sharp leaves…are they not a problem? Where is the science which backs up these claims? We certainly can’t find any. It seems that most websites simply repeat the same text without any backup scientific data.
Cortaderia selloana is primarily diocious, meaning it produces male and female flowers on different plants. For sake of full disclosure, hermaproditic plants (with both sexes) have been observed in the wild. Since the most showy plants are female, that’s virtually all that’s commercially grown, unless someone grows a seed strain. Having grown Cortaderia selloana for sixty years, including some from seed, we have yet to see a single garden seedling. Perhaps there are areas in the country where it shouldn’t be grown, and if so, we hope you will share the URL of the scientific papers that document this. Hardiness zone is Zone 6b-10b.
I know that different plants behave differently in different areas and habitats, with different companion plants. But I have to disagree with you on this one, at least as far as it goes in the region where I live (far northern California along the coast). No, I do not have scientific papers to share (I’m not a professional botanist), but I have lived here over 40 yrs and I can attest to coastal areas overwhelmed by pampas grass and have seen many clearcuts (also not a fan of clear-cutting) taken over by pampas grass and scotch broom. If they were short-term successional stages, that’d be one thing, but once pampas grass gets established, it appears it is there to stay….unless painstakingly weed-wrenched out one by one in a given area. And then there’s the seedbank….
You are correct that each region is different. We’re also not surprised that disturbed habits may be invaded as you describe. In many parts of the country, a climax forest would kill off early successionary plants, but in open grasslands, this may not occur, and as you described there are obviously not better adapted native plants to outcompete the cortaderia. As we all know, in nature, the best adapted plants win. Thanks for the report from CA.
I checked the website and found the bureaucrats in the Ca. Dept of Fish and Wildlife (CDFW) are a busy crew;
California endangered species act (CESA)
Native plant protection act (NPPA)
California environmental quality act (CEQA)
Natural community conservation act (NCCPA)
California desert native plants act (CDNPA)
Not only is this invasive and damaging to many ecosystems, it escapes easily, and it burns like nobody’s business. If you live in — or even near — a fire-prone area ( pretty much all the western states ) and you put this near your house Aside from damaging the neighborhood, you’re asking for trouble.
A simple Google search for peer reviewed articles about the invasive nature of pampas grass reveals many.
We agree that Cortaderia is indeed quite flammable, and is not a good idea in fire prone regions. As per finding scientific peer-reviewed papers on Google, we would appreciate those citations, since our very deep dive both on Google, Google Scholar, and through the greater University Library system reveled none. All of the research papers that showed up were the identical repeated claims of invasiveness with no scientific data backup. Please share. Thanks.
Just searching Google Scholar for “pampas grass invasive” turned up this paper, which has a large number of citations around the negative effects and damage of Pampas Grass as an invasive species.
https://onlinelibrary.wiley.com/doi/full/10.1111/rec.14175
“Nowadays, Pampas grass is a widespread invasive species in California (Lambrinos 2001), New Zealand (Than & Aliaga 2010), South Africa (Robinson 1984), and southern Europe (Basnou 2009), particularly in Portugal (Ministério do Ambiente 2019) and Spain (Gobierno de Cantabria 2017). This species can significantly change the natural and seminatural habitats, threatening the conservation of native vegetation (Domènech et al. 2006; Gallastegui & Prieto 2010). In fact, considering both environmental and socio-economic impacts, Pampas grass achieved the highest overall impact score when compared with other alien grasses in a review study conducted in South Africa (Nkuna et al. 2018). Additionally, it is responsible for pollen allergies or respiratory distress in most sensitive people (Fernández et al. 2017), extending the period of grass allergies in Northern Spain (and probably other locations as well) for about 3 months every year (RodrÃguez et al. 2021), and for skin cuts due to its sharp leaves (González et al. 2020). In Portugal and Spain, Pampas grass has been included in the national lists of invasive species since 2019 (Ministério do Ambiente 2019) and 2013 (MAGRAMA 2013), respectively. The species is being considered, but has not yet been included on the European Union’s list of invasive alien species (European Commission 2014), although Cortaderia jubata, a closely related species, is already on the list.”
You need to know that this plant genus has been destroying California coastal and intercoastal habitat. I and many before me have been working extremely hard to remove C. seloana and C..jubata for decades. Why don’t you go and look on California Invasive Plant Council /CAL IPC’s website and read all about it?
You’re making money off of destroying native habitats which is unconscionable and disgusting. You should know better or maybe you honestly don’t and that’s why you’re doing this stupidity! such a pity… can’t understand how you people can sleep at night.
Wow…that’s some serious anger, since we’ve never advocated planting pampas grass in California or do we think it should be planted there. We do, however, try to teach people to put everything horticultural in perspective. In terms of non-native species that crowd out or severely affect native habitats in California, pampas grass is way down on the list. At the top of the list would be the nearly 40 million Homo sapiens that call the state home, with 57% of those also having non-native pets. Then there is the 43 million of California’s 100 million acres that are used to produce non-native agricultural crops used to feed the non-native humans. It also makes me wonder if the people there are as passionate about ridding the state of those pesky non-native honeybees, which have completely changed pollination patterns and plant distribution. All of these cause far more ecological disruption than pampas grass will ever do. The amount of land invaded with pampas in miniscule in comparison. That said, we’re glad you’re passionate about the natural world, and wish you the best in your eradication attempts.
October 2023 I traveled by car w a friend from Portland, OR to Ventura, CA. Until going inland to avoid the Big Sur road outages we saw countless pampas grass in the edges of the Redwood Forests. It was with great surprise that we saw pampas grass in Tillamook, then all the way down into California. There were no apparent efforts to extirpate that I could discern.