The speaker wanders through summer woods and pays close attention to everything in them. The poem is stocked with plant names, like enchanter's nightshade, jumpseed, stinkhorn and squawroot, scattered between small encounters: a deer fly in the hair, a spider that eats its web each night, a shell-less mollusk with swiveling eyestalks. The speaker is a little wary, wielding a walking stick like a fencer's foil, but mostly curious and humble. "These woods are far stranger / than anything I can write" sounds like an admission that description will always fall short.
The mood is damp, close and quietly wondering. Even the falling tree, which could feel ominous, is followed by a wood peewee that just keeps singing its two notes. The ending, where the bird wishes the clouds would never part, suggests contentment with the gloom and the dimness. The speaker seems to feel the same way, happy to stay in the shade and keep looking.