Thirty years ago I was living in San Francisco, scheduled to give a talk at U.C. San Diego, and on the way to SF airport I found myself thinking there was no need to deal with airports that day, and decided to drive on to San Diego. I gave the talk and had several days to drive back up. I came inland and made my way to Sequoia National Park, not the first time I’d been there but the first time in spring.

I remember that trip especially for dogwoods blooming below the giant sequoias – the most m...