USA National Phenology Network

Biennial: A plant which lives two years, usually forming a basal rosette of leaves the first year and flowers and fruits the second year.

Calibration plant species: The calibration plant species component of the USA-NPN Plant Phenology Program consists of a set of 20 plants selected to help "calibrate" phenological measurements across the USA. These native and introduced plants have broad distributions and are ecologically or economically important. The USA-NPN integrates observations on calibration species to get "the big picture" of plant responses. USA-NPN observers are encouraged to include at least one calibration species in their monitoring projects. Widespread observation of calibration species is needed so that the collective monitoring data for these plants can be integrated with climate measurements across the nation.

Canopy: A layer of vegetation elevated above the ground. It can refer to the layer of leaves surrounding an individual tree or shrub, or to the continuous layer of vegetation that comprises the top layer of a forest.

Cloned plant:Genetically identical plants. The cloned plant species component of the USA-NPN Plant Phenology Program consists of a small set of cloned plant species, including the cloned lilac, to eventually be distributed across the entire nation.

Clonal: syn. Clone: A group of individuals originating from a single parent plant by vegetative reproduction.

Coniferous: Bearing cones or strobili.

Deciduous: Falling off, as leaves from a tree; not evergreen; not persistent.

Evergreen: Having green leaves through the winter; not deciduous.

Forb: Herbaceous (non-woody) flowering plants that are not graminoids (grasses, sedges and rushes).

Herbaceous: With the characteristics of an herb; not woody.

Perennial: A plant that lives three or more years.

Phenology: The study of periodic plant and animal life cycle stages and how these are influenced by seasonal and interannual variations in climate. Non-biological systems also exhibit annual or period stages coupled with changes in environmental conditions (e.g., ice-in and ice-out of lakes and rivers); although this is sometimes referred to as phenology, we prefer to reserve the term phenology for biological events, and the term seasonality for non-biological events.

Phenological event: A precisely defined point in the annual life cycle of a plant or animal, generally marking the start or end point of a phenophase. The occurrence of a phenological event can be pinpointed to a single date and time (in theory, if not in practice). Examples include the opening of the first flower on a plant, the end of leaf fall on a tree, the first appearance of a particular songbird species in spring, or the start of fish migration up-river to spawn. (Note: The definition of the term “phenological event” has not yet been standardized and varies among scientists. The definition presented here reflects our usage of the term on the USA-NPN website.)

Phenophase: An observable stage or phase in the annual life cycle of a plant or animal that can be defined by a start and end point. Phenophases generally have a duration of a few days or weeks. Examples include the period over which newly emerging leaves are visible, or the period over which open flowers are present on a plant. (See also phenological event) (Note: The definition of the term “phenophase” has not yet been standardized and varies among scientists. The definition presented here reflects our usage of the term on the USA-NPN website.)

Regional plant species: The regional plant species component of the USA-NPN Plant Phenology Program consists of a set of ~200 native or introduced plant species that have more localized distributions than calibration species, or that are particularly important in certain locales or regions of the nation in terms of ecological processes, biological diversity, conservation, economics, or human culture.

USDA plant hardiness zone: The USDA Hardiness Zone Map divides North America into 11 separate zones; each zone is 10°F warmer (or colder) in an average winter than the adjacent zone.

Variety: A category in the taxonomic hierarchy below the species and subspecies level.