Marrubium vulgare - L.
Common Horehound
Other English Common Names: Horehound, White Horehound
Other Common Names: horehound
Taxonomic Status: Accepted
Related ITIS Name(s): Marrubium vulgare L. (TSN 32561)
Unique Identifier: ELEMENT_GLOBAL.2.141400
Element Code: PDLAM0Z010
Informal Taxonomy: Plants, Vascular - Flowering Plants - Mint Family
Kingdom Phylum Class Order Family Genus
Plantae Anthophyta Dicotyledoneae Lamiales Lamiaceae Marrubium
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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: Marrubium vulgare
Conservation Status

NatureServe Status

Global Status: GNR
Global Status Last Changed: 22Mar1994
Rounded Global Status: GNR - Not Yet Ranked
Nation: United States
National Status: NNA
Nation: Canada
National Status: NNA (22Mar1994)

U.S. & Canada State/Province Status
United States Alabama (SNA), Alaska (SNA), Arizona (SNA), Arkansas (SNA), California (SNA), Colorado (SNA), Connecticut (SNA), Delaware (SNA), District of Columbia (SNA), Florida (SNA), Georgia (SNR), Hawaii (SNA), Idaho (SNA), Illinois (SNA), Indiana (SNA), Iowa (SNA), Kansas (SNA), Kentucky (SNA), Louisiana (SNA), Maine (SNA), Maryland (SNA), Massachusetts (SNR), Michigan (SNA), Minnesota (SNA), Mississippi (SNA), Missouri (SNA), Montana (SNA), Nebraska (SNA), Nevada (SNA), New Jersey (SNA), New Mexico (SNA), New York (SNA), North Carolina (SNA), Ohio (SNA), Oklahoma (SNA), Oregon (SNA), Pennsylvania (SNA), Rhode Island (SNA), South Carolina (SNA), South Dakota (SNA), Tennessee (SNA), Texas (SNA), Utah (SNA), Vermont (SNA), Virginia (SNA), Washington (SNA), West Virginia (SNA), Wisconsin (SNA), Wyoming (SNA)
Canada British Columbia (SNA), Nova Scotia (SNA), Ontario (SNA), Quebec (SNA), Saskatchewan (SNA)

Other Statuses

NatureServe Global Conservation Status Factors

Other NatureServe Conservation Status Information

U.S. States and Canadian Provinces
Color legend for Distribution Map
NOTE: The distribution shown may be incomplete, particularly for some rapidly spreading exotic species.

U.S. & Canada State/Province Distribution
United States AKexotic, ALexotic, ARexotic, AZexotic, CAexotic, COexotic, CTexotic, DCexotic, DEexotic, FLexotic, GA, HIexotic, IAexotic, IDexotic, ILexotic, INexotic, KSexotic, KYexotic, LAexotic, MA, MDexotic, MEexotic, MIexotic, MNexotic, MOexotic, MSexotic, MTexotic, NCexotic, NEexotic, NJexotic, NMexotic, NVexotic, NYexotic, OHexotic, OKexotic, ORexotic, PAexotic, RIexotic, SCexotic, SDexotic, TNexotic, TXexotic, UTexotic, VAexotic, VTexotic, WAexotic, WIexotic, WVexotic, WYexotic
Canada BCexotic, NSexotic, ONexotic, QCexotic, SKexotic

Range Map
No map available.

Ecology & Life History Not yet assessed
Economic Attributes Not yet assessed
Management Summary Not yet assessed
Population/Occurrence Delineation Not yet assessed
Population/Occurrence Viability
U.S. Invasive Species Impact Rank (I-Rank)
Disclaimer: While I-Rank information is available over NatureServe Explorer, NatureServe is not actively developing or maintaining these data. Species with I-RANKs do not represent a random sample of species exotic in the United States; available assessments may be biased toward those species with higher-than-average impact.

I-Rank: Medium/Low
Rounded I-Rank: Medium
I-Rank Reasons Summary: Common weed of disturbed places; Marrubium vulgare was originally introduced in US for medicinal properties; it may escape into native species habitats where it has the potential to become dense.
Subrank I - Ecological Impact: Medium/Insignificant
Subrank II - Current Distribution/Abundance: Medium
Subrank III - Trend in Distribution/Abundance: Medium/Low
Subrank IV - Management Difficulty: Medium
I-Rank Review Date: 26Mar2004
Evaluator: Fellows, M.
Native anywhere in the U.S?
Native Range: Native to Europe, Asia, northern Africa and some Atlantic Islands (Canary, Madeira and Azores) (Weber 2003).

Download "An Invasive Species Assessment Protocol: Evaluating Non-Native Plants for their Impact on Biodiversity". (PDF, 1.03MB)
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Screening Questions

S-1. Established outside cultivation as a non-native? YES
Comments: (Kartesz 1999).

S-2. Present in conservation areas or other native species habitat? Yes
Comments: (APRS 2001; LACNPS, Undated).

Subrank I - Ecological Impact: Medium/Insignificant

1. Impact on Ecosystem Processes and System-wide Parameters:Medium significance/Insignificant
Comments: Inferred from preference for disturbed habitats, yet no discussion in literature re: succession, nutrient capture, etc.

2. Impact on Ecological Community Structure:Low significance
Comments: Shrub (Kartesz 1999). Forms dense stands in arid grasslands that alter community structure (Weber 2003).

3. Impact on Ecological Community Composition:High/Low significance
Comments: Forms monoculture stands over large areas, reducing native species richness (Weber 2003). Reduces establishment and growth of native species in invaded areas (Weber 2003). Can displace the native community (APRS 2001).

4. Impact on Individual Native Plant or Animal Species:Unknown

5. Conservation Significance of the Communities and Native Species Threatened:Medium/Low significance
Comments: In California, present in coastal sage scrub, southern oak and riparian woodlands and grasslands (LACNPS, Undated). Also occurs in open, disturbed sites along roadsides and in pastures (Wilken and Hannah 1998).

Subrank II. Current Distribution and Abundance: Medium

6. Current Range Size in Nation:High significance
Comments: Occurs in nearly all states including HI and AK (Kartesz 1999). County distribution maps (NRCS 2004) show a scattered but frequent county-level occurrence in occupied states.

7. Proportion of Current Range Where the Species is Negatively Impacting Biodiversity:Low significance
Comments: Causes moderate impact in natural areas similar to habitats in Grand Canyon National Park (APRS 2001). Is considered a 'weedy pest' in Texas (Texas A&M 2000). However, it is not considered a noxious weed for agriculture or horticulture (Wilken and Hannah 1998).

8. Proportion of Nation's Biogeographic Units Invaded:High significance
Comments: Potentially occurs in more than 75% of ecoregions (TNC 2001) given it's occurence in nearly all states including HI and AK (Kartesz 1999).

9. Diversity of Habitats or Ecological Systems Invaded in Nation:Medium/Low significance
Comments: Dry forests, scrub- and woodland, arid rangelands, disturbed sites (Weber 2003). In California, present in coastal sage scrub, southern oak and riparian woodlands and grasslands (LACNPS, Undated).

Subrank III. Trend in Distribution and Abundance: Medium/Low

10. Current Trend in Total Range within Nation:Unknown

11. Proportion of Potential Range Currently Occupied:Low significance/Insignificant
Comments: Marrubium vulgare is hardy to plant zones 4a to 9b (Dave's Garden 2004), making it likely to spread to unoccupied states in the US, although the current range (Kartesz 1999) is over most of the potential habitat.

12. Long-distance Dispersal Potential within Nation:High significance
Comments: Seeds dispersed by animals and in streams (Weber 2003). Great potential for long-distance dispersal (APRS 2001). People continue to plant this species; available for purchase on the Internet (3/04).

13. Local Range Expansion or Change in Abundance:Moderate significance
Comments: Moderate rate of increase (APRS 2001). In Australia, M. vulgare is thought to establish first on roadsides and then disperse into neighboring areas (including pastures and natural areas) by animals (CSIRO-Europe 2001).

14. Inherent Ability to Invade Conservation Areas and Other Native Species Habitats:Medium/Low significance
Comments: Found in sites that were disturbed in the last 10 years to mid-successional areas (disturbed in the last 11-50 years) (APRS 2001).

15. Similar Habitats Invaded Elsewhere:Low significance
Comments: Canada (Kartesz 1999) and Australia, New Zealand, and South Africa (Wilken and Hannah, 1998; Randall, pers. comm.). Also in South America (Weber 2003). Habitats in Weber (2003) seem consistent with known habitats from US-only sources.

16. Reproductive Characteristics:Moderate significance
Comments: May accumulate a seed bank in large stands of Marrubium vulgare (Weber 2003) that is viable for more than 5 years (APRS 2001). Reproduces only by seed, which can be produced more than once per year at the rate of >1000 plant (APRS 2001). May resprout from roots (APRS 2001).

Subrank IV. General Management Difficulty: Medium

17. General Management Difficulty:Moderate significance
Comments: In fire-adapted communities, prescribed fire can kill M. vulgare plants and reduce the seed bank. The effect is enhanced by follow up treatment with herbicides (Weber 2003). Biological control may be an option (Wilken and Hannah 1998; APRS 2001).

18. Minimum Time Commitment:Moderate significance
Comments: Additional site visits required after initial fire (Weber 2003). A viable seed bank may persist for more than 5 years.

19. Impacts of Management on Native Species:Medium/Low significance
Comments: Control measures may negatively impact the community (APRS 2001).

20. Accessibility of Invaded Areas:High/Low significance
Comments: Present in some areas surrounding natural areas (e.g. Grand Canyon National Park) (APRS 2001).

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).

  • Alien plants ranking system (APRS) Implementation Team. 2001a. Alien plants ranking system version 7.1. Southwest Exotic Plant Information Clearinghouse, Flagstaff, AZ. Online. Available: (accessed 2004).

  • CSIRO-Europe Laboratory. 2001. Our Research. Horehound - Marrubium vulgare L., Lamiaceae. Available online: (accessed 20 August 2002).

  • Dave's Garden. 2000-2004. The plants database. Available: (Accessed 2004).

  • 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.

  • Kartesz, J.T. 1999. A synonymized checklist and atlas with biological attributes for the vascular flora of the United States, Canada, and Greenland. First edition. In: Kartesz, J.T., and C.A. Meacham. Synthesis of the North American Flora, Version 1.0. North Carolina Botanical Garden, Chapel Hill, N.C.

  • Los Angeles, California Native Plant Society (LACNPS). Undated. Invasive weeds and escaped exotics. Available ONLINE Accessed 25 March 04.

  • Texas A&M University. 2000. Uvalde Research and Extension Center, Texas A&M University System. Available ONLINE (accessed 2004).

  • The Nature Conservancy. 2001. Map: TNC Ecoregions of the United States. Modification of Bailey Ecoregions. Online . Accessed May 2003.

  • USDA, NRCS. 2004. The PLANTS Database, Version 3.5 ( . National Plant Data Center, Baton Rouge, LA 70874-4490 USA.

  • Weber, E. 2003. Invasive plant species of the world: a reference guide to environmental weeds. CABI Publishing, Cambridge, Massachusetts. 548 pp.

  • Wilken, D. and L. Hannah. 1998. Channel Islands National Park Fact Sheet on Marrubium vulgare. Santa Barbara Botanic Garden. December 15 last update. Online. Available: (accessed 2004).

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