Hydrologic Designations
Hydrologic, or soil moisture, designations describe a plant's tolerance to soil saturation.
Critical Site Products specializes in production of local-source native plants. In order to increase the long-term success of a planting, CSP emphasizes the importance of native plant specification and use in landscapes as appropriate to the natural hydrologic conditions where you are likely to find them.
For each native plant in our database, we have identified which of five natural soil types is considered its natural habitat. Utilize the 'Plant Search' feature to narrow your selection of plants for a specific hydrologic designation.
The hydrologic designations are:
| • | OBL, or Obligate Wetland - Occurs almost always under natural conditions on wetlands. |
| • | FACW, or Facultative Wetland - Usually occurs on wetlands, but occasionally found on non-wetlands. |
| • | FAC, or Facultative - Equally likely to occur on wetlands or non-wetlands. |
| • | FACU, or Facultative Upland - Usually occurs on non-wetlands but occasionally found on wetlands. |
| • | UPL, or Obligate Upland - Almost always occurs on non-wetlands. |
Native plants listed on our website have been assigned the hydrologic designation for the Central Plains per the USDA. If a "+" follows a hydrologic designation (such as FAC+), that species naturally occurs on sites near the wetter end of the spectrum in that designation. Similarly, a "-" following a designation connotes that species to be found on sites at the drier side of the spectrum in that designation.
These national indicators reflect the range of estimated probabilities of a species occurring in wetlands versus non-wetlands across the entire distribution of the species.
Data and definitions are abstracted from the National List of Vascular Plant Species, US Fish and Wildlife Service, 1988.
We also offer a small selection of transitional plants selected from native species for their outstanding horticultural characteristics. These transitional plants can be used to enhance native plantings in many urban landscapes. The plants are designated by "(Transitional Plant)" after the common name on the plant detail page.
