Mentha pulegium

Mentha pulegium_pennyroyal JM Di Tomaso
Photo courtesy Joseph DiTomaso

Synonyms: Mentha daghestanica Boriss.; Pulegium dagestanicum (Boriss.) Holub; Pulegium vulagare Mill.

Common names: pennyroyal; European pennyroyal; grows-in-a-ditch

Mentha pulegium (pennyroyal) is a perennial mint (family Lamiaceae) with a variable habit, ranging from low-growing, spreading plants to lanky, upright sub-shrubs. Although considered uncommon in much of California, pennyroyal occurs in the Sierra foothills, Central Valley, and most coastal counties from the Mexican border to Oregon. It is common as an obligate wetland indicator species in seasonally inundated soils of valley bottomlands, usually below 1,640 feet (500 m) elevation. Pennyroyal grows in flooded or seasonally wet areas: seeps, streamsides, vernal pools and swales, marshes, and ditches. Although pennyroyal is considered moderately invasive in wetlands its ecological impacts are not well documented. It clearly prospers in habitats that were once dominated by native plants, suggesting that it may have displaced some species. In particular, the flora of vernal pools may have suffered loss of habitat through the introduction of pennyroyal.

Rating: Moderate

Cal-IPC Resources

  • Plant Assessment Form - Information gathered by Cal-IPC on the impacts, rate of spread, and distribution of invasive plants in California. Does not include management information.
  • CalWeedMapper - Statewide maps, climate models, and reports.
  • Cal-IPC News - Our quarterly newsletter. Each issue is available as a pdf.
  • Cal-IPC Symposium Proceedings - Presentations and papers from our annual Symposium.
  • Don't Plant a Pest! - Select your region to find non-invasive alternatives to ornamental species. Also see our statewide brochure on trees.

Other Resources

Symposium Presentations

  • Connick, S. and M. Gerel (2004). Partnering to prevent invasions of plants of horticultural origin. California Invasive Plant Council Symposium 2004. Ventura, CA.
  • Pickart, A. J. and K. S. Wear (1999). The ecology of Parentucellia viscosa in dune wetlands. California Exotic Pest Plant Council Symposium '99. Sacramento, CA, California Exotic Pest Plant Council.
  • Quinn, L., B. Davis, et al. (2006). Does horse manure harbor invasive plants? Cal-IPC Symposium. Rohnert Park, CA.

Cal-IPC News Articles

  • Connick, S. and M. Gerel (2005). Don't sell a pest: A new partnership to prevent plant invasions through horticulture. Cal-IPC News. 13: 4-5,14.
  • Madison, J. (1996). Highways as corridors of dispersal. CalEPPC News. 4: 9.