This ongoing data package, which began in 1992, contains monthly plant phenological observations by species at the 15 Net Primary Production (NPP) study sites at the Jornada Experimental Range (JER) or Chihuahuan Desert Rangeland Research Center (CDRRC) in Dona Ana County, New Mexico, USA. Sites were selected to represent the 5 major ecosystem types in the Chihuahuan Desert (upland grasslands, playa grasslands, mesquite-dominated shrublands, creosotebush-dominated shrublands, tarbush-dominated shrublands). For each ecosystem type, three sites were selected to represent the range in variability in production and plant diversity; thus the locations are not replicates. A transect at each site is monitored monthly to assess the following phenological stages for each species: dormancy, non-reproductive status, budding, flowering, and fruiting. Sampling methods in the first years of the study monitored all plant species present but have been changed to focus on specific species at each site.