The Sempervirens Alliance is a slow, non-narrative, non-fiction phenomenological meditation on the Redwoods' Umwelt and intersubjectivity with a human hiker, using the language of cinematography to elucidate these philosophical perspectives. The film weaves together five years of research in forest semiotics, multi-species anthropology, the science of plant sensing, bioelectricity, and temporal perception, with a touch of mysticism.