Friday, February 18, 2005

Helping the Monarch Butterfly

"Monarch butterflies' numbers drop sharply" was an article in the newspaper today.

This winter there's about a 75% fewer monarchs observed on their Mexican overwintering grounds. Tree poaching in their mountain fir forest overwintering preserves may be partly responsible for the reduction. Adverse factors in their summering ground in North America -- genetically modified crops and a much cooler than usual spring and summer last year -- also have hurt them. [The reported population fluctuation may not affect us here in the San Francisco Bay area so much, since many of our monarchs over-winter here in California, as in Pacific Grove.]

Monarchs are less evident where I live than decades ago, and loss of milkweed patches is a major cause. Monarch caterpillars eat milkweed -- true milkweed, Asclepias -- and little else. The largest patch I knew of in Cupertino is now an upscale housing development without milkweed. The local native host is narrowleaf milkweed, Asclepias fascicularis.

A few times I've heard of people planting a narrowleaf milkweed and the caterpillars eating the poor little plant to the ground! However, the plant usually survives and comes back the next year and continues to slowly spread underground into a little colony over the years.

Though not exactly a California native plant, the Mexican sunflower, Tithonia rotundifolia, is a great favorite among late summer nectar plants for the adult butterflies.

One of the best native plants for butterflies of all kinds is the Calfornia Buckeye tree, Aesculus californica. I've seen up to seven species of butterflies simultaneously nectaring on one tree! It typically blooms in mid to late May.

Narrowleaf milkweed image is from from the Web site of Edgehill Mountain Park, San Francisco.


At 3:42 AM, Blogger google nut said...

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