The USA-NPN calibration plant species program consists of a set of 18 native or
introduced plant species distributed across the USA to create a spatial network of observations with sufficient overlap to allow inter-correlation of species responses across the entire nation.
Click on the plant names below for a printable identification guide that includes pictures, identifying characteristics, phenological observations and distribution area. (*All downloadable materials require the free Adobe Reader.) More identification guides will be coming soon.
| USA-NPN Calibration Species | |
| Common Name | Scientific Name |
| Aspen | Populus tremuloides |
| Alfalfa | Medicago sativa |
| Apple | Malus pumila |
| Big bluestem | Andropogon gerardii |
| Blue grama | Bouteloua gracilis |
| Canada thistle | Cirsium arvense |
| Chokecherry | Prunus virginiana |
| Common dandelion | Taraxacum officinale |
| Eastern redcedar | Juniperus virginiana |
| Forsythia | Forsythia x intermedia |
| Pinyon pine spp | Pinus edulis/monophylla |
| Ponderosa pine | Pinus ponderosa |
| Ragweed spp | Ambrosia artemisiifolia/psilostachya |
| Red maple | Acer rubrum |
| Spotted knapweed | Centaurea stoebe (syn C. maculoba) |
| Switchgrass | Panicum virgatum |
| Woods strawberry | Fragaria virginiana |
| Western wheatgrass | Pascopyrum smithii (syn Agropyron smithii) |