The Mexican tea plant, or Mexican bush sage as it is sometimes called, refers to the flowering perennial shrub Salvia leucantha. This sage is native to Mexico and parts of Guatemala and has become a popular ornamental plant, especially in warmer climates. However, there is some debate over whether Mexican bush sage has become an invasive species in certain areas or if it remains benign.
The Mexican bush sage is considered an aggressive grower and spreader in optimal climates, but is not officially classified as an invasive species. It has naturalized in some southern states and Hawaii, but so far has not caused significant environmental harm. More research is needed to determine if sage requires active management as an environmental weed. Home gardeners should take care to prune back spreading clumps and prevent unwanted spread into natural areas.
Native Range and Habitat
Salvia leucantha is native to the highlands of central and eastern Mexico, with a range extending from Hidalgo and Querétaro down through Oaxaca. It occurs at elevations between 5,000 and 8,200 feet in pine and pine-oak forests, growing in semi-shade. S. leucantha grows up to 5 feet tall and 3 feet wide in the wild. It produces velvety gray-green leaves and showy purple flower spikes from fall through winter.
Introduction to the United States
Mexican bush sage was introduced to the United States as an ornamental garden plant around 1839. Early botanists praised it as one of the most beautiful salvias for its long season of vivid purple blooms. The plant quickly became popular in California gardens and was later planted across the southern states from California to Florida.
More recently, Mexican sage has gained favor as a low-maintenance landscaping shrub, valued for its drought tolerance and ability to thrive in full sun. It is commonly incorporated into xeric gardens and naturalized landscapes in the Southwest. Commercial production expanded to meet demand, with over 2 million plants sold annually in the US by the 1990s.
Naturalization in the Southern United States
Mexican bush sage has naturalized, or established wild populations, in parts of the southern United States. According to the USDA, it has been reported to naturalize in:
- Southern Nevada
- New Mexico
- Western Texas
- South Carolina
- Southern Florida
The plant spreads both by seed dispersal and vegetative reproduction from rhizomes. Birds likely spread the seeds from landscape plantings into adjacent natural areas. Escaped sage has colonized disturbed sites like roadsides, edges of arroyos and drainage ditches, fallow fields, and abandoned mined land.
Mexican bush sage exhibits some weedy traits that allow it to naturalize readily outside of cultivation. Key traits include:
- Vigorous growth: Salvia leucantha grows rapidly, up to 5 feet in one season, outcompeting slower growing native plants.
- Prolific reproduction: Mature plants produce hundreds of seeds that germinate readily without pre-treatment. The species also spreads vegetatively via rhizomes.
- Drought tolerance: Mexican sage thriving in hot, dry conditions where water is scarce gives it an advantage in arid climates.
- Generalist: Sage tolerates a wide range of soil types, pH ranges, light levels, and temperatures. It thrives in many habitats.
- Long bloom period: Extended fall and winter flowering provides ample time for pollination and seed production.
Naturalized Range in the United States
Salvia leucantha has moved beyond cultivated gardens and become widely naturalized in California and the desert Southwest. According to the USDA, it has been documented to persist and reproduce in wild areas within these states:
- California – extensive naturalization reported
- Nevada – naturalized populations in Clark County and scattered occurrences elsewhere
- Arizona – scattered distribution, including Tucson area
- New Mexico – common in some areas from desert grassland up to ponderosa forests
Sage has also naturalized to a more limited extent in parts of Texas, Louisiana, Mississippi, Alabama, Georgia, and Florida. The plant seems to pose the greatest risk of becoming invasive within the arid Southwest.
Mexican bush sage has naturalized extensively across California, occurring in at least 35 counties from San Diego to Siskiyou. It has spread into many plant communities, including chaparral, coastal sage scrub, oak woodlands, coniferous forests, and desert habitats. Sage appears on numerous noxious weed control lists for national forests and parks in the state.
Areas of greatest concern outside California include Tucson, Arizona where sage is reported to be “spreading rampantly,” as well as parts of southern Nevada and New Mexico. Research in New Mexico found sage present in 52% of study quadrats in desert grassland and 21% of ponderosa pine forest plots.
Despite evidence of substantial naturalization, Mexican bush sage has not been designated as an invasive plant species in any legal sense within the United States. However, some researchers and land managers have recommended the plant be recognized as an emerging environmental weed.
Invasive Plant Lists
Salvia leucantha currently appears on these preliminary invasive plant lists and watches:
- Arizona Native Plant Society Watch List
- New Mexico Exotic Plant Research List – Spreading significantly
- Texas Institute of Applied Environmental Research Watch List
However, sage is not considered a noxious weed by any state or federal authorities so control is not mandated.
Researchers note that Mexican bush sage exhibits traits of an invasive plant, especially within the desert Southwest. These include:
- Rapid vegetative spread by rhizomes, allowing dense clonal thickets to form.
- Prolific seed production and recruitment within natural habitats.
- Thrives in full sun, able to colonize open disturbed areas.
- Alters habitat suitability for native species.
These factors indicate sage has potential to become a more aggressive invader, but further research is still needed before declaring the species invasive in any region.
Research into environmental impacts from naturalized Mexican sage remains limited. Some potential concerns based on preliminary studies include:
Alteration of Plant Communities
In New Mexico, researchers found that sage may reduce establishment of native species from seed banks based on sampling across 52 study sites. Plots with sage present had 50% fewer native species on average.
Like other woody salvias, Mexican bush sage likely increases fuel loads. Dense sage thickets could potentially increase fire risk and burn intensities in habitats not adapted to frequent fires.
High water use efficiency may allow sage to outcompete native plants in desert environments, as documented in some other invasive shrubs.
However, no studies have quantified the actual impacts of sage invasion on biodiversity, ecosystem functions, or resources. Further monitoring and targeted research is warranted to clarify its long-term impacts.
Is Mexican Bush Sage Considered Invasive in Other Countries?
Beyond its native range in Mexico, Salvia leucantha has also been introduced as an ornamental plant to other regions with mild climates. However, it has not been reported to become invasive in these countries:
Grown as a garden plant, especially in New South Wales and Victoria. Listed as naturalized, but not considered a problematic plant.
Occurs as an occasional garden escapee, but not showing invasive tendencies. Not considered an ecological threat.
Planted in parts of Spain, Italy, and Greece, but not reported to naturalize or become weedy in the region.
The absence of invasiveness in these regions indicates sage may be best adapted to invade areas with hot, semi-arid climates similar to its native habitat.
Management and Control
No coordinated management programs currently target Mexican bush sage as an environmental weed. However, recommendations have been provided for controlling naturalized populations and minimizing further spread:
Small infestations can be effectively eliminated by hand pulling or digging out plants. Juvenile plants can be hand pulled when soil is moist. Larger plants will require digging out the root system.
Mowing or cutting plants can reduce vigor and seed production of sage stands. However, rhizomes may resprout after cutting, requiring follow up treatment.
Foliar glyphosate sprayed on foliage during active growth can provide good control. Cut-stump applications are also effective. Follow label guidelines for rates in natural areas.
Fire will top-kill sage plants and reduce their vigor and seed output. However, rhizomes will likely resprout after burns. Multiple repeated burns over time may control infestations.
Gardeners should not plant Mexican bush sage adjacent to natural areas. Remove spent flowers to prevent seed spread. Seek non-invasive alternatives for landscaping needs.
Mexican bush sage has undoubtedly naturalized and spread from cultivation in parts of the southern United States, especially in the Southwest. However, conclusive evidence is lacking on whether these wild populations currently cause significant ecological harm. More targeted research will help clarify if active management of sage as an invasive species is justified, or if the plant remains a relatively innocuous introduced species in naturalized ranges at this time.