Piloblephis rigida (Bartr. ex Benth.) Raf.
Pennyroyal
Federal Protection: No US federal protection
State Protection: No Georgia state protection
Global Rank: G3G4
State Rank: S1
Element Locations Tracked in Biotics: Yes
SWAP 2015 Species of Greatest Conservation Need (SGCN): No
SWAP 2025 Species of Greatest Conservation Need (SGCN): Yes
2025 SGCN Priority Tier: High Conservation Concern
Element Occurrences (EOs) in Georgia: 2
Habitat Summary for element in Georgia: Myrtle oak scrub
Short-lived shrubs 4 - 28 inches (10-70 cm) tall, erect or mound-forming, with a woody base and many, very hairy, non-woody branches. The leaves are up to 0.5 inch (0.5 - 1.2 cm) long, opposite, evergreen, narrowly lance- or needle-shaped, stiff, thick, and aromatic when crushed. Flower clusters are compact, densely flowered, round or cylindrical, hairy, held at the tips of branches. Flowers are about 0.3 inch (7 - 8 mm) long, white to pale purple, with 4 stamens and two lips, the lower lip with dark purple spots and 3 rounded lobes. After the flowers fall, the compact, fruiting “head” becomes showy, pale, and conspicuously hairy.
There are few species of woody mints in Georgia’s Coastal Plain and no other with compact, densely flowered inflorescences and needle-like leaves. Georgia Basil (Clinopodium georgianum), another woody mint with pink or lavender flowers, occurs in dry woodlands in the Piedmont and Coastal Plain; its leaves are oval and thin-textured.
Florida Pennyroyal is the only species in the genus Piloblephis. One other rare, shrubby mint occurs in Georgia’s Coastal Plain.
Calamintha ashei (synonym Clinopodium ashei, Ohoopee Wild Basil), a low shrubby mint, is found in Georgia’s Coastal Plain. It occurs on ancient sand dunes along and near the Ohoopee River and in disturbed areas through these habitats. For more information, see: https://www.georgiabiodiversity.org/portal/profile?group=plants&es_id=18031
Sandy pine flatwoods, sandhills, and oak/saw palmetto scrubs on ancient dunes on the Trail Ridge and barrier islands. Often with Myrtle Oak (Quercus myrtifolia).
There is no published information on the life history of Piloblephis rigida, but research on other woody mints suggests that its flowers are pollinated by bees and other insects that use the prominent lower lip as a landing platform. Research on other mints with strongly aromatic leaves and that occupy dry, sandy habitats confirms that their roots release allelopathic compounds that prevent germination of other species’ seeds, thus reducing competition in their vicinity; this may be true of Piloblephis rigida but similar research has not been published for this species.
Piloblephis rigida blooms nearly year-round in Florida, where it is common, with peak bloom in late winter and spring. In Georgia, surveys should probably be carried out in the spring and early summer.
The Trail Ridge and barrier islands of southeast Georgia; Florida.
Conversion of habitat to pine plantations, pastures, and commercial and residential development; sand mining, off-road vehicle traffic.
| Threat 1 | Threat 2 | Threat 3 | |
|---|---|---|---|
| General Threat | Pollution | Climate change & severe weather | None |
| Specific Threat | None | None | None |
Piloblephis rigida is ranked S1 by the Georgia Department of Natural Resources, indicating that it is critically imperiled in the state. Two populations have been discovered in Georgia, both on private land, but neither have been confirmed in several decades.
Protect sandhills, sand ridges, and ancient dunes from conversion, development, and mining. Limit off-road vehicle use on dunes and sand ridges.
GADNR. 2019. Element occurrence records for Piloblephis rigida. Georgia Department of Natural Resources, Wildlife Resources Division. Social Circle, Georgia.
Huegel, C.N. 2010. False Pennyroyal – Piloblephis rigida. Hawthorn Hill Wildflowers, Florida. http://hawthornhillwildflowers.blogspot.com/2010/11/false-pennyroyal-piloblephis-rigida.html
NatureServe. 2020. Piloblephis rigida comprehensive report. NatureServe Explorer: an online encyclopedia of life. NatureServe, Arlington, Virginia. http://explorer.natureserve.org/servlet/NatureServe?searchName=Piloblephis+rigida
Small, J.K. 1933. Manual of the southeastern flora. New York Botanical Garden, New York.
Taylor, W.K. 1998. False Pennyroyal, Piloblephis rigida. Florida wildflowers in their natural communities. University Press of Florida, Gainesville.
Weakley, A.S. 2015. Flora of the southern and mid-Atlantic States. University of North Carolina Herbarium, University of North Carolina, Chapel Hill. http://www.herbarium.unc.edu/flora.htm
Linda G. Chafin
Linda G. Chafin, 20 April 2020: original account
