Well, we’ve fallen a little behind in choosing a wildflower of the week, so we’re going to make up for it by choosing silver lupine (Lupinus albifrons): one of California’s most ubiquitous flowers. Although it leaks across the border a little into Southern Oregon and Northern Baja, this perennial shrub is a true Alta Californian. These are blooming near Soberanes Creek in Garrapata State Park – one of the many State parks scheduled to be “closed” this year.
The name “silver” comes from the silver tint of the leaves. These are blooming along the Boronda Trail.
The silver leaves make L. albifrons easily distinguishable from Yellow Bush Lupine (Lupinus arboreus), the common bush lupine of our coastal terraces – many of which produce blue/purple, rather than yellow, flowers. Note the smooth green, silver-free leaves of this L. arboreus coming into bloom on Granite Point at Pt. Lobos.
A member of the Pea Family (the Fabaceae), silver lupine can be found blooming in our area from soon after the fall rains begin, on into the summer. It prefers dry hillsides and the disturbed soil along the edges of roads and trails. This one is growing in the proposed East Molera Wilderness with Pico Blanco in the background.
Silver lupine’s flowers generally range from sky blue to magenta …
Silver lupine is toxic to livestock, but dearly loved by a wide variety of insects, including these bordered plant bugs (Largus californicus?). It is also highly prized by bees and is suspected of being very important to native pollinators. Silver lupine is, in fact, one of only three species of lupine that hosts San Francisco’s extremely endangered Mission Blue Butterfly (Icaricia icarioides missionensis), whose range is now restricted to Twin Peaks, San Bruno Mountain and a small area around Ft. Baker. These butterflies are notable for having a symbiotic relationship with a species of ant. The caterpillars secrete a sweet substance that the ants find delectable and, in return, the ants protect the caterpillars from predators. The caterpillars also absorb the lupine’s toxins, making the adult butterflies unpalatable to most birds. They do not have a defense, however, against the loss of the lupine they depend on – and the urbanization of their territory hasn’t left much lupine behind.
As a legume, silver lupine is handy for building up the soil, as it is capable of fixing nitrogen from the air. These were vigorously growing and vibrantly blooming in an area burned down to bare soil by the Chalk Fire only seven months before.
Silver lupine blooming on the south face of the Double Cone.