Cortaderia jubata
People who don’t know better think that pampas grass is beautiful–and in most ways, it is. The flowers of this gigantic grass are showy plumes that wave in the wind like horses’ manes or pennants. The leaves are long and trailing, and as wide as a large man’s finger. The whole plant, including the lofty bloom, can be up to 20 feet tall.
But this striking plant is also a noxious invasive, imported from Argentina and the Andes. It grows quickly in disturbed areas like cliff faces and road cuts, and forms large patches that crowd out smaller or slower growing native species.
There are actually two species that are commonly called pampas grass–Cortaderia jubata and C. selloana. Both thrive along the coast, but jubata (sometimes also called jubata grass) is restricted to coastal areas, while selloana also grows farther inland. Jubata plumes are purple or lilac, tending towards white as they age. This species can also be distinguished from its cousin because it holds its plumes quite high above the mound of leaves.
Both species of pampas grass bear their male and female flowers on separate plants (the botanical word for this is “dioecious,” as opposed to most plants which are “monoecious” and have their male and female parts on the same plant, often in the same flower). But while C. jubata reproduces asexually and lives for ten years or more, C. selloana can only reproduce if another plant of the opposite sex is nearby. 
Flowers Of Marin 
So is the Pampas grass sold as an ornamental also on the California noxious plant list? I see a lot of it in yards of the Midwest.
Well, as I understand it, yes. And it may not be as much of a problem there as it is here because the climate may keep it more under control–but that’s just a hopeful guess, since often there’s a big disconnect where nurseries keep selling plants that pose (sometimes substantial) problems for the local environment.
Well, it’s definitely something to keep in mind. It’s true that some plants are unable to compete as well on the ‘fringe’ of their habitat and that may be the case here, but it’s also true that people are generally unaware of what plants are ‘noxious’ in their area. The whole thing is complicated by the fact that the plant is already out of its native range, so how it will survive, adapt, or thrive is a bit of a guessing game.