Semantic annotation of LTER data will improve the precision and recall of EDI repository searches. To accomplish this, we envision an incremental process beginning with a foundational layer of semantic metadata for all data packages using the LTER controlled vocabulary as a starting point. This information may then be used to facilitate the organization of thematic working groups to identify concepts requiring annotations of greater complexity. In this workshop we will focus on forming the semantic base layer across all LTER data by tagging data packages with terms from the LTER Controlled Vocabulary (LTER-CV), which will be leveraged as a map to equivalent representations in the Environment Ontology (ENVO). Our goals for this workshop are: 1.) annotate LTER data packages with terms from the LTER-CV where gaps exist; 2.) identify and propose any terms that are missing from the LTER-CV. This workshop will result in an LTER/ENVO knowledge graph to facilitate more complex annotations in the future and to serve as an experimental space to inform the effectiveness of semantic annotation strategies. 2/3 of this workshop will be devoted to hands-on activities. Everyone is welcome. Bring your laptop.