We were scouting for a vibrant yellow bush called French Broom. It’s an aggressive plant from France, which will take over our sensitive landscapes, crowding out native plants. We were on a mission to scope it out, map it, and remove it from a steep hillside of San Bruno Mountain, nestled between an industrial area and a suburban neighborhood of Daly City. It was an early March day, but the sun beat down on us with the intensity of a summer afternoon as we scaled the steep hillside. I watched the ground carefully, looking before each step so as to avoid crushing native species like soap root, footsteps of spring, and Douglas Iris, and also to avoid slipping down the rocky slope as I was carrying a 20-pound weed wrench. Suddenly, I spied a small, low-growing plant with heart-shaped leaves. A few feet farther up the slope I saw the telltale yellow flowers, looking like a garden “pansy,” peaking out of the mass of green. It was California Golden Violet, Viola pedunculata!
Sometimes called yellow pansy, or Johnny-Jump-Up, the viola is a host plant for about a dozen species of Fritillary butterflies, including the Callippe Silverspot, Speyeria callippe, also known as the Callippe Fritillary. These butterflies are classified as endangered, making our Viola populations even more critical, as the caterpillars feed on their leaves. We pull broom from these steep, rocky hillsides in order to preserve critical grassland habitat for the violas and Callippe Silverspots, along with other important host plant species. The viola can be found at San Bruno Mountain in a variety of areas, especially on open, grassy slopes and chapparal. If you see it, be careful not to step on it! Tiny butterfly eggs may be on the ground surrounding the plants, and the elusive Callippe caterpillar may be quietly eating their fill. These violas bloom from February to April, providing food for a wide variety of pollinators, and otherwise are small and unassuming low-growing plants. Adult butterflies can be seen flying from May to August. Although our parks are currently closed to humans, we can enjoy some images of this beautiful, vibrant, and critically important plant, which continues to be home and nourishment for many amazing creatures in our parks.