Thalictrum cooleyi - Ahles
Cooley's Meadowrue
Other English Common Names: Savanna Meadowrue
Other Common Names: Cooley's meadowrue
Taxonomic Status: Accepted
Related ITIS Name(s): Thalictrum cooleyi Ahles (TSN 18665)
Unique Identifier: ELEMENT_GLOBAL.2.137457
Element Code: PDRAN0M040
Informal Taxonomy: Plants, Vascular - Flowering Plants - Buttercup Family
Kingdom Phylum Class Order Family Genus
Plantae Anthophyta Dicotyledoneae Ranunculales Ranunculaceae Thalictrum
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Concept Reference
Concept Reference: Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
Concept Reference Code: B94KAR01HQUS
Name Used in Concept Reference: Thalictrum cooleyi
Conservation Status

NatureServe Status

Global Status: G1
Global Status Last Reviewed: 27Jun2017
Global Status Last Changed: 09Jun2017
Ranking Methodology Used: Ranked by calculator
Rounded Global Status: G1 - Critically Imperiled
Reasons: An endemic of the southeastern Coastal Plain in Florida, Georgia, and North Carolina. Twenty-one extant occurrences and at least six occurrences have been lost to conversion of habitat to silviculture or agriculture and these factors continue to threaten some of the few remaining populations. Throughout the range, fire suppression has increased the relative rarity of suitable habitat (which was probably never abundant) and contributed to the species' overall decline. Mulitple roadside populations are susceptible to extirpation. In addition, the species poor seed viability, potentially low genetic diversity, The remaining populations will need active management with prescribed burns in order to persist. Additional genetic studies of the species entire range are needed to determine if some populations (GA) are hybrids or a distinct species.
Nation: United States
National Status: N1

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Florida (S1), Georgia (S1), North Carolina (S1)

Other Statuses

U.S. Endangered Species Act (USESA): LE: Listed endangered (07Feb1989)
Comments on USESA: Thalictrum cooleyi was proposed endangered by the USFWS on April 21, 1988 and determined endangered on February 7, 1989.
U.S. Fish & Wildlife Service Lead Region: R4 - Southeast

NatureServe Global Conservation Status Factors

Range Extent Comments: Occurs in North Carolina (Brunswick, Columbus, Georgia, New Hanover, Onslow, and Pender Counties), Georgia (Worth and Doughtery Counties), and Florida (Walton County) (USFWS 2009).

Area of Occupancy: 6-25 4-km2 grid cells
Area of Occupancy Comments:  

Number of Occurrences: 21 - 80
Number of Occurrences Comments: There are 21 extant element occurrences (12 in North Carolina, 1 in Florida, and 8 in Georgia). The five year recovery plan describes 12 extant populations in 2008 but since then two new subpopulations and two populations were discovered since the plan was written (USFWS 2009). A number of occurrences are extirpated, historic due to fire suppression and silviculture and agricultural activities (USFWS 1989, 2009).

Population Size Comments: Most element occurrences have less than 100 plants but a couple have around 400 plants.

Number of Occurrences with Good Viability/Integrity: Few (4-12)

Overall Threat Impact: Very high
Overall Threat Impact Comments: The main threat to this species is alteration or destruction of its habitat by suppression of fire, and by forestry and agricultural, and road maintenance activities. All of the 11 occurrences that are in North Carolina are small and are threatened by area activities which include bulldozing, conversion of land into pastures, and draining of land. In addition, some of the populations near roads are threatened by road maintenance. Specifically, one occurrence near a road was covered by fill material. In Florida, the one occurrence has been impacted significantly by timber operations (USFWS 1999). However, this species requires some disturbance to maintain open habitat and can withstand mowing and some timber operations if done properly. This species cannot, however, withstand bulldozing, drainage, conversion of land to pine plantations, and direct application of herbicides (USFWS 1989). In addition, because the populations of Thalictrum cooleyi are small and easily accessible, vandalism and increased collection could result (USFWS 1989).
The small populations may be inherently vulnerable since the species is rhizomatous and number of genetic individuals may be low and because it doesn't produce many seeds and apparently lacks seed dispersal mechanisms (USFWS 1989).

Short-term Trend: Decline of 10-30%
Short-term Trend Comments: In North Carolina, two element occurrences are extirpated, one is historic, and an additional three had no plants found during the last survey.

Intrinsic Vulnerability Comments: Thalictrum cooleyi is intrinsically vulnerable in several ways. It is rhizomatous, so the number of ramets is far greater than the number of genets. It is dioecious, so the populations where only one sex persists are particularly vulnerable. It produces few seeds and apparently does not have a seed dispersal mechanism (USFWS 1989).

Other NatureServe Conservation Status Information

Global Range: Occurs in North Carolina (Brunswick, Columbus, Georgia, New Hanover, Onslow, and Pender Counties), Georgia (Worth and Doughtery Counties), and Florida (Walton County) (USFWS 2009).

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map

U.S. & Canada State/Province Distribution
United States FL, GA, NC

Range Map
No map available.

U.S. Distribution by County Help
State County Name (FIPS Code)
FL Walton (12131)
GA Dougherty (13095), Worth (13321)
NC Brunswick (37019), Columbus (37047), Onslow (37133), Pender (37141)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
03 Northeast Cape Fear (03030007)+, Waccamaw (03040206)+, Lower Flint (03130008)+, Lower Choctawhatchee (03140203)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
Basic Description: A small, rhizomatous, perennial herb with erect to lax stems, up to 1 m tall. Loose clusters of flowers are borne in June. The unisexual flowers lack petals, but the sepals are white, pale yellow, or pale green with lavender filaments. The leaves are narrow and lance-shaped. The fruits are single-seeded and winged. Phenology: Flowers appear mid to late June and fruit mature in August or September.
Technical Description: "Plant with a short, erect caudex. Stems sometimes slender and weak below, tending to be held erect by surrounding vegetation, sometimes more robust and stiffly erect, 4-8 dm tall. Lower and stem leaves petioled, the uppermost usually sessile. Leaflets varying, linear, lanceolate, elliptic, or oblong-oblanceolate, all except the latter usually entire and 4 or more times as long as wide, the oblong-oblanceolate ones 1-3-toothed-lobed distally and 2-3 times as long as wide; upper surfaces green and glabrous, the lower pale, glaucous, margins revolute. Plant dioecious. Sepals ovate, oblong, or obovate, 1.5-2 times as long as wide. Filaments slender below, tending to become curled, somewhat dilated distally, longer than the anthers; anthers linear-elliptic, or oblong when not fully developed, 1-2 mm long. Achenes sessile, ellipsoid, ridged and furrowed, the ridges sinuous, sometimes branching, the hooked, persistent style base about 2 mm long, body 4-6 mm long" (Godfrey and Wooten, 1981).
Diagnostic Characteristics: Thalictrum cooleyi differs from other similar species in the Leucocoma section of this genus by its lavendar instead of white filaments (although this character may not be consistent even within the same population), its much narrower leaflets (narrowly lanceolate instead of oblong to ovate) and its fewer leaf divisions (Kral 1983). It can be distinguished from Thalictrum revolutum its leaflet narrowness that is four to 26 times as long as it is wide, lacking lobing in the majority of the leaflets, and the absence of hairs, glands, or papillae on lower leaflet surfaces, petioles, peduncles, and achenes. It can be vegetatively distinguished from most other herbs with compound leaves by having basal leaves that are two or more times ternately compound. However this characteristic may not occur in the smallest individuals. This species has a high chromosome count and ploidy level (Boyer 1994).

T. cooleyi can also be distinguished from other Thalictrums, besides T. revolutum, growing with it by its long, narrowly lanceolate, mostly entire, upper stem leaflets; stamens with lavendar tinted stalks and its lax habit (it leans on other vegetation). Also, other Thalictrums have short-stalked, knobbed hairs found on the undersides of the leaves and on the fruits (Patrick et al. 1995).

Reproduction Comments: Flowering in June (Radford et al, 1968). The winged, single-seeded fruits mature in August and September (Lowe et al. 1990), but the seed life is presumably short. A dioecious species, Thalictrum cooleyi has separate male and female flowers that are primarily wind pollinated. Species has low germination rates. Seeds require overwintering (cold stratification), forming a seed bank for at least 1 year,  and fire (to open canopy) for germination (Dietrick 2016). This species is found to have low genetic variation in and between populations (Fortner et al. 2016). The species grows from rhizomes.
Ecology Comments: This species can regenarate from rhizomes and from buds along the caudex (Fortner et al. 2016). 
Palustrine Habitat(s): Bog/fen, HERBACEOUS WETLAND
Terrestrial Habitat(s): Savanna
Habitat Comments: Sunny, moist places such as open, savanna-like forest edges and clearings, wet savannas over calcareous clays, and ecotones between wet savannas and non-riverine swamp forests. Soils are basic, sandy loams. Also on roadsides and power line rights-of-way in former savannas.

It grows on circumneutral soils in wet pine savannas, grass-sedge bogs, and savannalike areas, often at the border of intermittent drainages or swamp forests. Boggy savannah-like borders of low woodlands, roadside ditches, and power line rights-of-way. Usually associates with some type of disturbance, e.g., clearings, the edges of frequently burned savannas, power line right-of ways which are maintained either by fire or mowing, and roadside edges. Typically on Grifton soil.

This plant is found on fine sandy loams that are at least seasonally (winter) moist or saturated and are only slightly acidic (pH 5.8-6.6). Sufficient moisture is criticial to plant vigor and reproductive effort. This plant occupies a narrow hydrological niche, where soil is moist to saturated but water does not stand above the soil surface.

This species occurs in moist to wet bogs and savannas and savanna-like openings on circumneutral soils and is dependent upon some form of disturbance to maintain the open quality of its habitat. Currently, artificial disturbances, such as power line and road right-of-way maintenance, and plowed firebreaks, are maintaining some of the openings historically provided by naturally occurring periodic fires (Murdock 1989).

This species grows in circumneutral soil in moist to wet savannas and savanna-like areas kept open by frequent fire or other disturbance.

"This borderline type of habitat would have been disturbed historically by naturally occurring savanna fires moving through at 1- to 5-year intervals, clearing litter from the soil surface and causing the cyclical advance and retreat of woody growth. A typical population of Cooley's meadowrue has robust reproductive plants among shrubs and in adjacent open savanna and repressed individuals in nearby dense shade" (Boyer 1994).

Economic Attributes Not yet assessed
Management Summary
Stewardship Overview: Prescribed burns are a necessary part of a management regime for this species. Active protection and managment is necessary for the future survival of the species because it occurs near where federal activities such as power line construction, maintenance and improvement, drainage alterations and permits for mineral exploration and mining take place (USFWS 1989).
Population/Occurrence Delineation Not yet assessed
Population/Occurrence Viability
Excellent Viability: An A-ranked population of Thalictrum cooleyi should have more than 500 plants.
Good Viability: A B-ranked population of Thalictrum cooleyi should have between 200 and 500 plants.
Fair Viability: A C-ranked population of Thalictrum cooleyi should have between 50 and 200 plants.
Poor Viability: A D-ranked population of Thalictrum cooleyi should have fewer than 50 plants.
Justification: The rank specification for Thalictrum cooleyi are based on current populations and expert opinion.
Key for Ranking Species Element Occurrences Using the Generic Approach (2008).
Date: 13Jan2005
Author: Amoroso
Notes: (Weakley 1994)

U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
NatureServe Conservation Status Factors Edition Date: 26Jun2017
NatureServe Conservation Status Factors Author: Mansberg, L. (1985), rev. A. Weakley (rev. Maybury, K. 6/96), rev. M. Franklin 02/2004, rev. L. Oliver 7/2004, rev. A. Treher (2017)
Management Information Edition Author: MARY RUSSO, NCNHP, rev. L. Oliver (2004)
Element Ecology & Life History Edition Date: 28Jul1992

Botanical data developed by NatureServe and its network of natural heritage programs (see Local Programs), The North Carolina Botanical Garden, and other contributors and cooperators (see Sources).

  • Dietrick, E. 2016. Embryo Development, Seed Bank Potential, and Germination of the Federally Endangered Herb of Pine Savannas, Thalictrum cooleyi. East Carolina University. Thesis. Online: 

  • Fortner, A. R, C. L. Jolls, and C. Goodwillie. 2016. Important biological knowledge for management of Cooley's Meadowrue (Thalictrum cooleyi), a federally endangered endemic of pine savannas. Natural Areas Journal 36: 288-301.

  • Fortner, A.R., L.J. Claudia, and C. Goodwillie. 2016. Important Biological Knowledge for Management of Cooley's Meadowrue (Thalictrum cooleyi), a Federally Endangered Endemic of Pine Savannas. Natural Areas Journal 36(3): 288-301.

  • Godfrey, R.K., and J.W. Wooten. 1981. Aquatic and wetland plants of southeastern United States: Dicotyledons. Univ. Georgia Press, Athens. 933 pp.

  • Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.

  • Kral, R. 1983c. A report on some rare, threatened, or endangered forest-related vascular plants of the South. USFS Tech. Publ. R8-TP 2, Atlanta, GA. 2 Vol. 1305 pp.

  • Lowe, D.W., J.R. Matthews, and C.J. Moseley, eds. 1990. The official World Wildlife Fund guide to endangered species of North America. Beacham Publishing, Washington, D.C. 1180 pp.

  • Patrick, T.S., J.R. Allison, and G.A. Krakow. 1995. Protected plants of Georgia: an information manual on plants designated by the State of Georgia as endangered, threatened, rare, or unusual. Georgia Dept. Natural Resources, Wildlife Resources Division, Georgia Natural Heritage Program, Social Circle, Georgia. 218 pp + appendices.

  • Radford, A.E., H.E. Ahles, and C.R. Bell. 1968. Manual of the vascular flora of the Carolinas. Univ. North Carolina Press, Chapel Hill, NC. 1183 pp.

  • U. S. Fish and Wildlife Service (USFWS). 1989. Endangered and threatened wildlife and plants; determination of endangered status for Thalictrum cooleyi (Cooleyi's Meadowrue). Federal Register 54 (24): 5935-5938.

  • U.S. Fish and Wildlife Service (USFWS). 1993. Availability of the agency draft recovery plan for Cooley's meadowrue for review and comment. Federal Register 58(153): 42741.

  • U.S. Fish and Wildlife Service (USFWS). 2009. Cooley?s Meadowrue (Thalictrum cooleyi) 5-Year Review: Summary and Evaluation. U.S. Fish and Wildlife Service Southeast Region Ecological Services Raleigh, North Carolina. 20 pp.

  • U.S. Fish and Wildlife Service. 1988. Proposed endangered status for Cooley's meadowrue. Federal Register 53(77): 13220-13223.

  • U.S. Fish and Wildlife Service. 1994. Cooley's Meadowrue Recovery Plan. U.S. Fish and Wildlife Service, Atlanta, GA. 29 pp.

  • U.S. Fish and Wildlife Service. 2008. Cooley's Meadowrue (Thalictrum cooleyi) 5-Year Review: Summary and Evaluation. U.S. Fish and Wildlife Service, Southeast Region, Ecological Services, Raleigh, NC. Available online at

  • Wilcyznski, C. J. 1993. A three-year study on population dynamics of Cooley's meadowrue (Thalictrum cooleyi) at Lanier Quarry Pender County, North Carolina. for USFWS grant K88SE05 (?)

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