Whatever it is, it's pervasive and not very localized. I never notice it getting stronger near any of the trails where we hike -- it's more a general odor one notices while driving along forest roads. That makes it hard to narrow it down to a specific plant.
Googling wasn't entirely enlightening, but it did suggest that the most likely culprit is a mushroom. Various species of Mycena mushrooms apparently emit a chlorine-like odor, especially when they're growing on wood. Chlorine smells are also reported from Marasmius oreades, the "fairy ring" or "scotch bonnet" mushroom, and from Amanita chlorinosma and A. polypyramis. But I didn't find anything about widespread seasonal blooms of any of these mushrooms.
So the mystery remains, and I guess all that's left is to remember, when hiking in the redwood forest at this time of year, to stop and smell the mushrooms.
[ 11:36 Jul 29, 2006 More nature | permalink to this entry | comments ]