Trichostema brachiatum
False pennyroyal
Image of Trichostema brachiatum

Photo by Susan R. Crispin 

Key Characteristics

Annual forb of sandy soils or alvar; stem branched and finely glandular-hairy, with opposite elliptic leaves, aromatic when crushed; tubular bluish-purple flowers arise from the upper leaf axils with short, glandular-hair pedicels.

Status and Rank

  • State Status: T
  • State Rank: S1
  • Global Rank: G5


County NameNumber of OccurrencesYear Last Observed
Distribution map for Trichostema brachiatum

Updated 5/15/2018. Information is summarized from MNFI's database of rare species and community occurrences. Data may not reflect true distribution since much of the state has not been thoroughly surveyed.


False pennyroyal occurs in dry prairies, sandy areas, thickets, roadsides, railroad rights-of-way, and occasionally on disturbed sites. In the northern portion of the state, it may also be found on limestone bedrock grasslands of Drummond and Thunder Bay Islands.

Natural Community Types


For each species, lists of natural communities were derived from review of the nearly 6,500 element occurrences in the MNFI database, in addition to herbarium label data for some taxa. In most cases, at least one specimen record exists for each listed natural community. For certain taxa, especially poorly collected or extirpated species of prairie and savanna habitats, natural community lists were derived from inferences from collection sites and habitat preferences in immediately adjacent states (particularly Indiana and Illinois). Natural communities are not listed for those species documented only from altered or ruderal habitats in Michigan, especially for taxa that occur in a variety of habitats outside of the state.

Natural communities are not listed in order of frequency of occurrence, but are rather derived from the full set of natural communities, organized by Ecological Group. In many cases, the general habitat descriptions should provide greater clarity and direction to the surveyor. In future versions of the Rare Species Explorer, we hope to incorporate natural community fidelity ranks for each taxon.

Associated Plants

Tumble grass, little bluestem, big bluestem, fall witch-grass, sheep sorrel, bitter milkwort, dwarf-dandelion, poverty grass, nut-grass sp, shining sumac, and sassafras. In alvar habitat, it may occur with northern white cedar, balsam fir, sand cherry, ground juniper, buffaloberry, bulrush sedge, Hill's thistle, Alaska orchid, flattened spike-rush, prairie dropseed, and fragrant sumac.


This species requires active management (fire, brush-clearing) to maintain or re-establish a prairie character where it occurs in southern Michigan. In northern Michigan, it primarily requires protection of habitat from direct disturbance, including ORV use and excessive foot traffic, and may also be susceptible to local alterations of hydrological regime.

General Survey Guidelines

Random meander search covers areas that appear likely to have rare taxa, based on habitat and the judgment of the investigator.

Survey Methods

Page Citation

Michigan Natural Features Inventory. 2007. Rare Species Explorer (Web Application). Available online at [Accessed Aug 16, 2018]


Survey References

Technical References

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