20th Street Garden Update | Summer 2014

Lovely Lepidoptera – Butterflies found on 20th Street

June 2014 photo 1
Cabbage White on statice flower, 20th St

Who doesn’t love a butterfly? A caterpillar, that’s another thing. It’s hard to remember that we need those leaf-munching, worm-like creatures in order to have beautiful, delicate flying creatures. No caterpillars, no butterflies. It’s that simple.

Butterflies sip nectar from a variety of plants, but Mom will lay her eggs only on specific plant families or sometimes only certain species within a family. That’s because their baby caterpillars can only eat those specific plants. (The childhood favorite book The Very Hungry Caterpillar is of course fictional.) Each type of butterfly has a different host plant (plant where eggs are laid). Loss of host plants contributes to extinction of the species. San Francisco is currently home to only 35 species of butterflies.

June 2014 Photo 2
Eggs of Cabbage White on the underside of kale. Photo by Elizabeth Gomm.

The familiar Cabbage White is the most common butterfly in San Francisco. Unfortunately, their host plants are all in cabbage and radish family. Vegetable gardeners must look sharp to rub out eggs found on the underside of the leaves or soon lose their kale, collard greens, cabbage, broccoli, cauliflower, bok choy and other related crops to the voracious green caterpillars. On 20th Street, cabbage whites come to drink nectar but we have none of their host plants in the garden. We can enjoy looking at them without having to curse them.

June 2014 photo 3
Red Admiral on statice flower, 20th and Alabama.

The Red Admiral is related to the more famous Monarch, Buckeye and Painted Lady. Around here, it’s most active in spring and late summer. Their host plants are in the nettle family.

June 2014 Photo 4
Pellitory. Photo by Dave/Dandelion and Burdock

Both stinging nettle and pellitory, a common weed, serve as host plants for Red Admiral in San Francisco. If you have these plants, consider keeping some in your garden instead of pulling them all. These aren’t growing on 20th Street either but they are found in many vacant lots and neglected corners, especially where there is some shade.

June 2014 photo 5
Unidentified Painted Lady on Hooker’s Evening Primrose leaf, 20th St

This blurry photo (butterflies are fast!) is likely a kind of Painted Lady. There are 3 kinds in San Francisco: Painted Lady, West Coast Painted Lady and American Painted Lady. The host plants for the first 2 are in the mallow family, which include hollyhock and hibiscus as well as a California native, Flannel Bush (Fremontodendron californicum) and many weedy mallow species. The American Painted Lady lays its eggs on pearly everlasting, which is wild semi-weedy plant in the daisy family.

I’m using the word weed a lot. It’s true that many butterfly host plants are considered weeds – by humans. But the more we learn about nature, the more we are reminded that every plant has a purpose.

June 2014 photo 6
Bee plant (right) and Pennisetum ‘Bunny Tails’ grass

The native and drought-tolerant plants on 20th Street are growing so successfully that there are few weeds. We do have some host plants though. Bee plant and perennial grasses on Florida Street are hosts for the Common Buckeye and various Skippers. Sticky monkey flower on 20th is host to the Variable Checkerspot, a locally rare species. Nectar for adult butterflies is abundant in Statice, California Aster and Sedum ‘Autumn Joy.’ We can’t be all things to all butterflies, but we hope to support as many as we can.

June 2014 photo 7
Sedum ‘Autumn Joy’ growing on Florida Street

Visit http://www.sfbutterfly.org and http://www.natureinthecity.org to find out more about identifying and supporting local butterflies.

Ellyn Shea is a gardener and garden consultant in San Francisco. Visit her at http://www.garden-guidance.com

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