The California Phenology (CAP) Collections Network is a collaborative plant specimen digitization project of 22 (and growing) California herbaria. With the help of professional and amateur botanists, native plant society members, gardeners, and citizen scientists of all kinds, the CAP network aims to produce nearly one million fully digitized (imaged, transcribed, and georeferenced) specimen records over four years and score the phenology (i.e., reproductive traits such as flowering or fruiting) of each record. These data provide a critical resource for research, education, and outreach about plants, biodiversity, ecology, evolution, and more. Phenological data especially provide insight into how plants in the highly biodiverse California Floristic Province respond to climate change, land use change, and other effects of human activities.