National Germplasm Resources Laboratory (NGRL) botanists are responsible for maintaining the taxonomic and nomenclatural integrity of the scientific names in GRIN. NGRL maintains an active collection of monographic and floristic literature from throughout the world to assist our activities. Through ongoing research into all current taxonomic literature, consultations with taxonomic botanists, and systematic reviews of GRIN scientific names for various plant families, the most recent taxonomy and nomenclature are incorporated into GRIN. For major crop genera, GRIN taxonomic work may often involve interaction with other USDA scientists for those crops and their Crop Germplasm Committees (CGC).

The taxonomic and nomenclatural decisions accepted in GRIN are based on various considerations. GRIN family taxonomy is based, with a few more recent exceptions, on the APG-3 classification (Bremer et al., 2009). Taxonomic decisions at lesser ranks ideally reflect the views of recognized taxonomic specialists for various plant groups as determined from published literature, such as monographs, revisions, or contributed treatments to floras, or from direct consultation for review of GRIN taxonomic information. Evidence from molecular phylogenetic studies, which is particularly relevant to decisions regarding generic taxonomy but seldom impacts species-level decisions, is also taken into account. Evaluating any proposed changes from such studies in relation to existing GRIN generic taxonomy, while nonetheless challenging, is guided by an assessment of the range of evidence presented, including the completeness of sampling, and the extent to which recognized specialists are participants in the underlying research or have embraced its conclusions. When a specialist opinion or specialist-generated literature is lacking, taxonomic decisions, particularly at species level, are based on the floristic literature. Floras are generally assigned greater weight than checklists, and modern floras are given greater consideration than older ones in preparing the GRIN treatment.

Other considerations being equal, when there are differences in taxonomic treatment or nomenclatural disputes, the GRIN treatment would generally be guided by current usage, with some evaluation of the impact of a change to our users and to the internal consistency of our treatment. In serving the agricultural scientists of NPGS, it is especially necessary to consider usage among agronomists and horticulturalists in addition to that of taxonomists. A requirement, however, is that all nomenclature adhere to the rules of the International Code of Nomenclature (McNeill et al., 2012).

Nomenclatural problems or discrepancies which appear and are unresolved in the literature often require that original references be consulted. The location of the NGRL on the Beltsville Agricultural Research Center, about 24 km northeast of Washington, D.C., also facilitates this work by providing access to several excellent libraries for historical and current botanical literature, including the National Agricultural Library (NAL), Library of Congress (LC), Smithsonian Institution (SI), and University of Maryland. The wealth of on-line botanical resources has now become indispensable for this purpose, especially those resources made available through the Biodiversity Heritage Library, the Digital Library del Real Jardín Botánico, the Gallica Digital Library, and Google Books.