Beau d’arc trees have very distinct growth rings. In June one fell across the creek where we live in South-Central Texas, and I’ve finally managed to recover some rings. I waded across the creek with a very sharp saw and cut two upper canopy branches from the downed beau d’arc. Hard work at 98 degrees F. One branch goes back to 1979 and nicely covers my 20 years of sunlight measurements (including UVB and PAR–photosynthetic radiation). I plotted the width of the individual beau d’arc rings against growing season rain and temperature. Rain and cool temps yield widest rings. Plotted brightness of beau d’arc early and late wood in each ring. So far no visually obvious relationship with PAR. (Ignore the vertical lines in the photo. The squiggly line is the intensity profile across the specimen.)

See some of my sun and sky data at www.forrestmims.org

This post made on 09 August 2010.