Almost all of the spring flowers have gone to seed and the winter grasses are dry and sere, but all over the dusty hills and along the roadsides summer flowers, like living gold are in bloom
June this year feels more like August. An early rainy season and unusually warm spring brought an early spring that favored weeds over native wildflowers and left behind dry hills and elevated fire risk. However, even with the current extreme conditions there are still summer wildflowers. summer wildflowers in the Santa Monica Mountains.
So much growth occurred in the Palisades Fire burn zone that it is now hard to imagine the scope of last year’s devastation. The portions of Topanga that burned the hills are now covered with rusty red bindweed vines and the drying stalks of phacelia—early bloomers that began to grow the second the first post-fire rains arrived. Their seeds will rest in the soil potentially for years, waiting for the next cycle of fire and rain.
Invasive, none-native black mustard dominated the landscape this winter, but it’s an opportunistic annual that grows fast and just as quickly goes to seed. The yellow flowers on the hillsides now are a mix of native and invasive species: from native tar weed, gumweed, and deer weed, to non-native yellow starthistles and hoary mustard.
These are adaptable, heat-tolerant plants that take advantage of a late blooming season when fewer flowers bloom. There are tradeoffs. Summer wildflowers face less competition for pollinators but they also have to flower and set seed during the dry season, when water is scarce.
The majority of the summer field flowers are yellow in the Santa Monica Mountains. This is true of both natives and invasive species. The color, derived from carotenoids in the soil, has a major advantage for plants, it requires less energy for the plant than more exotic shades like blue or red. But just because a flower appears yellow to humans doesn’t mean that insects see it the same way.
Many of those yellow flowers in bloom right now, even ones that appear almost the identical shade to humans, fluoresce under UV light, glowing with colors unseen by humans but visible to insect pollinators. It is estimated that more than a quarter of all flowering plants use ultraviolet colors to attract pollinators. Viewed under the right kind of UV light, even the common dandelion is transformed from sunny yellow to neon pink and violet. Insects see a very different world than we do.
It’s easy for us humans to overlook the less showy summer flowers, not only because we don’t see them the way insects do, but because they do not catch the human eye or move the soul the way the vivid orange of the spring poppies and the rich blues and purples of the lupine do. Instead, they are just part of the landscape, a dusting of gold on hills burned dusty brown by the summer sun. They may never receive a second glance, but each of these plants has a story. Some are food and shelter for butterflies, moths and bees; others are associated with culinary or medicinal traditions and uses; some are deadly poison or contain the potential to confer healing; all of them, native and non native have evolved to not only survive but to thrive in challenging conditions.
Here in the Santa Monica Mountains it sometimes feels like the invasive species have the upper hand, especially in summer when showy non-natives like Spanish broom, persistent ones like yellow star thistle, and the ubiquitous hoary mustard can dominate the landscape, but there are still many native species here, too.
The resin produced by the yellow flowers of the tall, daisy-like gum plant were once used by both the Chumash people and later European arrivals to treat coughs, sore throats, and other respiratory problems. The thick, clear, resinous gum was in demand for the pharmaceutical industry until the second half of the twentieth century.
The late Chumash healer Cecilia Garcia and her student, healer and associate professor of pharmacology James D. Adams, authors of Healing with Medicinal Plants of the West, wrote that the resin produced by this plant was “used in US and British hospitals and clinics for the treatment of tuberculosis and respiratory infections until 1960.” when a US law was passed that required “proof of clinical efficacy for all drugs.”
“No company was willing to perform clinical trials with gumplant for fear that a plant preparation could not be patented,” the authors conclude.
Scotch broom, a non native that has invaded the Santa Monica Mountains in recent decades, is more showy and fragrant than its native cousin, deer weed, Acmispon Glaber, but deer weed is also fragrant and colorful, and it plays an important role in fire recovery.
This member of the legume family is always present throughout the Santa Monica Mountains, but it tends to be especially abundant after a wildfire. Like many native chaparral plants that have adapted to life in the fire zone, its seeds will remain viable in the soil for years, waiting for the right conditions to germinate.
Deerweed fills in where larger shrubs burned, and disappear again when those plants have grown back. Like many members of this family, this species fixes nitrogen in the soil, and unlike the non-native grasses and other invasive species that compete with it, this species is fairly fire resistant.
The nineteenth century Chumash elder Kitsepawit, also known as Fernando Librado, provided much of what is now known about Chumash plant knowledge. He reported that deer weed was the only plant that the Chumash used to thatch sweat houses because it does not easily burn.
This plant is an important source of nectar for pollinators, attracting a spectacular assortment of butterflies, humming birds, and bees. An abundant bloom of deer weed can be detected from a distance not only by its sweet fragrance, but by the electrical buzzing of the bees.
In the spring, non-native black mustard dominates the hills, but by June any large expanse of golden flowers is likely to be the native slender tarweed, Deinandra fasciculata. Tarweed is a deeper, richer gold than mustard, it’s more particular about the ground it grows in, preferring alluvial soils and clay flats.
Ethnobotanist Jan Timbrook, the author of The Chumash Ethnobotany, describes how the dried stems of slender tarweed, Deinandra fasciculata, were bundled together to make brooms and whisks, and adds that the Chumash and other indigenous people gathered the seeds of for a food source, and used it to make a kind of pulverized meal called called pinole that could be mixed with water to make a porridge. Although that practice seems to have faded after the Spanish conquest of California, possibly because this plant, like so many others, began to face competition from aggressive invasive species.
Tarweed is a critically important flower for a host of native butterflies, moths, bees, wasps and other pollinators. The seeds are eaten by birds and small mammals.
Coast goldenbush, Isocoma menziesii, is a true late bloomer. It’s just starting to bloom and will peak in September. This is a key plant for wildlife producing abundant, nectar-filled flowers during the hottest, driest part of the year. The flowers are followed by oil-rich seeds late autumn and winter, just in time to provide a food source for migratory and overwintering birds. This plant is a perennial but it cannot regenerate after a fire. Instead, its seeds, borne on the wind, will recolonize the burn zone of a wildfire.
Even the most aggressive invasive species sometimes face competition from even more efficient interlopers. The black mustard that covered the hills in a sea of bright green and vivid yellow has entirely gone to seed, leaving man-high forests of dried and dead stalks and hundreds of millions of seeds behind, but this species’ smaller, scrubbier, duller, and infinitely tougher cousin, hoary mustard, Hirschfeldia incana, is still blooming on the roadside and trailside, in the garden, and along any patch of disturbed ground it can find.
This indestructible weed even pops back up after Caltrans has poisoned everything else in reach with herbicide. It’s more of a perennial than an annual, and can regrow from its roots after being weed-whacked. Like its bigger cousin, hoary mustard uses chemicals in its roots to discourage competition from other plants.
The only nice thing one can say about this invader is what the old lady said about the devil: “if nothing else, he’s persistent,” but even hoary mustard has its uses. It provides a food source for pollinators. Its seeds can be collected and ground up to make the condiment mustard. The flowers are edible and add a zippy bite to salads. The leaves are edible too, but only barely, and only at the start of the season. By June they are too tough and bitter for even the snails to tackle. The best thing to do with this plant is uproot it before it goes to seed.
There’s another, even less welcome invader that is blooming with enthusiasm along the side of the roads and in almost any other patch of disturbed ground right now: the yellow starthistle.
Sheep, goats, and even cattle eat the leaves of yellow star thistle before the plant’s spines grow—so can humans—but for horses this plant can be deadly.
Star thistle—Centaurea solstitialis—is native to Eurasia, but it arrived here via South America, in the nineteenth century. Although it looks delicate and pretty, this plant pushes out native plants, sucks the moisture out of the soil, and is armed with painfully sharp spines. The flowers of this thistle produce high-quality nectar and it is an important plant for the California honey industry.
A 1954 study in the Journal Neuropathology and Experimental Neurology on Nigropallidal encephalomalacia—the starthistle-related illness that kills horses—found that as many as 150,000 bee colonies used yellow starthistle as a primary source of pollen.
The practice of moving hives up and down the state to pollinate different crops may have contributed to the rapid spread of this species, but once established, this plant has its own ways of spreading and colonizing. Like the mustards, it produces “allelochemicals”—the plant version of chemical warfare.
These toxic compounds poison the soil, making it more difficult for other species of plants to germinate and grow, but they may also hold potential for human use.
Research published in the journal Plant Biology in 2023 found that these chemicals “are precisely what confers them ethnobotanical and medicinal properties.”
The authors reported that they found that “the species was rich in pharmaceutically active compounds and that the species had been traditionally used for medicinal purposes, as raw material, and as food.” They concluded that the “ethnobotanical uses were reported almost exclusively in its native range, plant species.”
The plant has put down deep roots in California. The knowledge of how to use it has stayed behind.
Summer is here. Those yellow flowers blooming by the side of the road may be any one of dozens of things, but they all have a name and a story. Some are fragrant, some are edible or medicinal, others are potentially toxic, all are part of life in the Santa Monica Mountains, and not just part of the landscape.
