How did weeds get to Southern California? One of the principal causes of habitat destruction, weeds threaten our region’s natural places. Constant maintenance and eradication is an absolute necessity as we battle against exotic invasive plants, and it’s beneficial to understand the origins of this enemy.
Weeds are here because people brought them here, sometimes deliberately, sometimes accidentally. Some were brought long ago, some only recently, but whatever the reason we have no one to blame but ourselves.
A common example is black mustard. Originally from Europe and one of the most widespread and recognizable weeds in California, it was supposedly scattered by Franciscan padres to mark the route of El Camino Real (which means it’s been here at least 300 years). The story is probably true, but it’s likely the missionaries also cultivated mustard for its food and medicinal properties, which is a common reason for the presence of many weeds.
Many common weeds in the Santa Monicas were likely introduced deliberately to the U.S. by European immigrants: mustards, horehound, milk thistle, fennel, common plantain (goose tongue), cheeseweed, castor bean, watercress… the list goes on. Some weeds have been brought accidentally, mixed in with the seed of a cultivated food crop, say perennial pepperweed contaminating sugar beet seeds or something. Others were brought as food for imported animals; red-stemmed filaree was likely brought as a forage plant for the livestock immigrants were importing. All in all the transportation of food, forage, and medicinal crops, seed, and plants is probably the most prevalent explanation for the presence of weeds.
But then we also brought a lot of them over because we liked the look of them or found them useful in some way. Eucalyptus trees are from Australia and they’re invasive, some species more than others. They were planted all over California from the late 1800s to the 1930s as a cash crop and also because we simply thought they were cool ornamentals.
Chinese immigrants brought Tree of Heaven here around the same time also as a fast-growing ornamental. Iceplant was planted for decades for erosion control along roadways and on beaches. It’s common along the entirety of California’s coast but is originally from South Africa.
There’s also money in weeds, at least for a time, as plenty of invasives were introduced by the nursery industry. Here in California common selling points for non-native plants that end up becoming invasive would be things like “erosion control,” “drought resistance,” and “fast growing.” Fountain grass is a terrible invasive (fast growing and drought resistant!), responsible for untold millions of dollars’ worth of habitat degradation and destruction, and incredibly still sold by some nurseries.
Same with pampas grass. Very pretty and striking, very destructive, and still sold by some nurseries. Mexican feather grass is a new ornamental grass gaining popularity and though it hasn’t been around long enough to become and invasive, it’s “fast growing” and “drought resistant” properties coupled with the ability to reseed itself means it’s probably just a matter of time until it’s a problem, too. Rule of thumb: if it’s “fast growing” and “drought tolerant” but not a native, skip it.
Because of growing awareness there’s generally less deliberate and accidental introduction of invasives today than in the past when we, A) didn’t understand how invasives would be a problem and, B) really seemed to enjoy nothing more than mowing down native flora and spreading pretty exotics everywhere. However the world is incredibly interconnected and there are people and animals and ships and planes crisscrossing the world every day, so we’re probably going to keep on having new, awful problems to deal with.