The NEON Biorepository’s plant collections provide a remarkably diverse archive of terrestrial and aquatic vegetation, spanning traditional herbarium vouchers, micro- and macroalgae, canopy foliage, litterfall, belowground biomass, and frozen plant tissues. Collected using standardized protocols across a geographically extensive network of field sites, these diverse materials capture multiple components of plant diversity, structure, and ecosystem function, from species-level identification to above- and belowground carbon and nutrient cycling. The combination of preserved vouchers, cryogenically stored tissues, and chemically and physically characterized plant materials supports taxonomic, genomic, biogeochemical, and ecological research. Linked to NEON’s long-term environmental measurements and contextual data, these collections offer a distinctive resource for comparing ecosystems, investigating plant–environment interactions, and tracking biodiversity and ecosystem change over time.