Updated: Wed, May 1, 2013, 2:16 pm Uploaded: Mon, Apr 29, 2013, 7:33 am
Butterflies and Edgewood Park
Volunteers wage a pitched battle with invasive grasses
These endangered Bay Checkerspot butterflies were released into Edgewood (County) Park and Natural Preserve in March 2011 in a second attempt to reintroduce the butterflies to their natural habitat. ==I Photo by Michelle Le/The Almanac==
On the infrequent occasions that Woodside's Edgewood (County) Park hosts a springtime rabble of Bay Checkerspot butterflies, they flit and flutter above fields of tiny flowers for 10 to 15 days, searching for mates and nectar. Each fertilized female will lay some 400 eggs at the base of the stem of the California dwarf plantain, if she can find one. With their missions complete, the butterflies then die.
Of those 400 eggs, two typically make it through the creepy crawly stage to hibernation and maturity, says park volunteer Bill Korbholz. In theory, the ecology works. The butterflies choose Edgewood because it is home to the right flowers. If the flowers are prolific, the caterpillars can find the right leaves to eat and make it through hibernation.
But this breeding cycle, when it is successful, is now due in great part to intervention by park volunteers. For example, on a spring day a year or so ago,volunteers tried to jump-start the process by releasing 4,000 to 5,000 Checkerspot caterpillars brought in from a South Bay park.
The flowers the caterpillars feed on face fierce, and unfair, competition for space and water in Edgewood's meadows. While the meadows appear pastoral, the serenity is an illusion. Oat grass and Italian rye grass, both invasive species, push out the flowers.
Fighting on behalf of the flowers, the San Mateo County Parks Department mows the grasses down before they go to seed.
"If we didn't do that, we wouldn't have a habitat. It really breaks my heart to see so many grasses here," Mr. Korbholz says. "Their nutrients are being stolen from them. ... I frankly feel we're losing the battle. ... I watch these grasses come in and multiply and take over. It's a sad, sad story, but we keep trying."
The invasive grasses employ windblown pollination and the county can't mow it all, so in every week of the year, volunteer "weed warriors" are out there trying to assist the survival of dwarf plantain, owl's clover and the rest, Mr. Korbholz says.
The areas of the meadows that are still mostly flowers are fenced off. Well before the volunteers cross that boundary, they brush the soles of their shoes to remove foreign seeds. Within the protected areas there are occasional patches of grass, but that is native bunch grass, Mr. Korbholz says.
The flowers, though small, are plentiful and make a vibrant living carpet, mostly in shades of yellow unless you look closely. Like their larger cousins, these flowers' common names reflect the enchantment of observers unencumbered by modernity: Ithuriel's Spear, Farewell to Spring, Tidy Tips, Blue-eyed Grass, Cream Cups and -- perhaps exemplifying an emphasis on the truth in the name rather than its beauty -- Hog Fennel.
The soil in the protected areas is rich in a mineral that the invasive grasses can't tolerate, but the flowers can, and it shows in the fields of flowers. "This, to me, I mean it doesn't get any better than this," Mr. Korbholz says surrounded by flowers. "It's spectacular. If I were a butterfly, this is where I'd hang out. Unfortunately, I don't see any."
Will enough caterpillars find enough plantain and owl's clover leaves to carry them through hibernation this year? We won't know until next spring.