IngredientsLewis's monkey flower (Erythranthe lewisii, also commonly called "great purple monkeyflower") is a perennial plant in the family Phrymaceae. It was formerly known as Mimulus lewisii, a scientific name assigned by Frederick Traugott Pursh in 1813; it was subsequently moved to the genus Erythranthe in 2012 by Guy L. Nesom and Naomi Fraga. Both the older name Mimulus lewisii and the currently accepted name Erythranthe lewisii appear throughout the scientific and commercial literature. The plant has no accepted varieties, but it has nine synonyms according to Plants of the World Online.
The genus name Mimulus is derived from the Latin word mime, meaning "actor" or "mimic," with the male diminutive -ulus, most likely referring to the mask-like appearance of the flowers. The species epithet lewisii is named in honor of explorer Meriwether Lewis. Common names in use include Lewis's monkey flower, Lewis' monkeyflower, and great purple monkeyflower. The plant is also referred to in horticultural trade as "purple monkey flower," "Lewis monkey flower," and carries the synonym Erythranthe lewisii.
Lewis's monkey flower is a perennial herb, with stem length ranging from 25 to 80 cm and individual leaves ranging from 20 to 70 mm. The vegetative tissue is covered with fine hairs. The plant is an upright herbaceous perennial with broadly lance-shaped, coarsely toothed, gray-green leaves without petioles. The simple blades are lanceolate to ovate with toothed (serrate) margins.
The flowers are medium in size, set on fairly long (30β70 mm) pedicels, and range in color from pale pink (generally found in the Sierra Nevada populations, sometimes separated as Erythranthe erubescens) to dark magenta (more common in the Cascade Range and Rocky Mountains populations), with a central pair of carotenoid-rich yellow nectar guides covered in trichomes on the lower lobe of the corolla. Occasional populations of white-flowered individuals (which do not express anthocyanin pigments in the corolla) are known. Blooming from early summer to early fall, the 2-lipped tubular flowers (approximately 5 cm long) are borne solitarily in the leaf axils. The mature capsule is 12β16 mm long.
Lewis's monkey flower is native to western North America from Alaska to California to Colorado, where it grows in moist habitat such as stream banks, and is generally found at higher elevations in montane areas. In particular, it is found at elevations between 5,000 and 10,000 feet. This is a mountain species that requires higher elevations, snow in winter, cool temperatures in summer, and plenty of water. It grows in wet areas, streambanks, and moist meadows at mid to high elevations in mountains, and often forms large showy clumps.
Lewis's monkey flower is pollinated by bees (primarily Bombus and Osmia), which feed off of its nectar and transfer its pollen. Although it is fully interfertile with its sister species, E. cardinalis, the two do not interbreed in the wild, a difference ascribed primarily to pollinator differences (E. cardinalis is pollinated by hummingbirds) in areas of overlap.
Together with other species in Erythranthe, Lewis's monkey flower serves as a model system for studying pollinator-based reproductive isolation.
Since the 1940s, the genus has been used as a model plant system in evolutionary and ecological genetics, and the genome of M. guttatus has been sequenced; information on the genomes of M. lewisii and M. cardinalis is also available. The genus shows great diversity, and even within species, variation in traits such as habitat specialization, floral divergence, and the fertility of hybrids can be observed; with the genetic data now available, the links between genes and observed traits can be studied.
When Meriwether Lewis and William Clark's Corps of Discovery started on their western trek to the Pacific Ocean in 1804, most of the plant species of western North America were still unknown to the scientific world. Although not formally trained as a botanist, Lewis had received some training from Dr. Benjamin Barton, the most prominent American botanist of the time.
Among the species Lewis and Clark first documented was the brilliant pink, or reddish-purple flower now called Lewis's monkey flower (Mimulus lewisii). Frederick Pursh, the 19th-century botanist who identified most of the expedition's collections, named the species in Lewis's honor in an 1814 publication and included a handsome color print of the species, taken presumably from material gathered by Lewis β although the actual specimen was apparently among those that were lost. Based on their journals, the explorers encountered Mimulus lewisii "on the head springs of the Missouri [River], at the foot of Portage hill," a site interpreted by botanical historian Wayne Phillips as the head of Trail Creek, Montana, just below Lemhi Pass.
Lewis's monkey flower (E. lewisii) belongs to the larger genus Mimulus / Erythranthe, which encompasses numerous species. Many species in the genus Mimulus (which includes Lewis's monkey flower) were used as food or medicine by First Peoples. The specific attribution of traditional uses requires careful attention to species identification, as historical records often documented genus-level practices without distinguishing between the many Mimulus species.
Documented uses for the related species Mimulus guttatus (yellow monkeyflower) by indigenous North American peoples provide context for the genus more broadly. Mimulus guttatus has been used for food and medicine by North American indigenous peoples: the Kawaiisu used a decoction of stems and leaves as a steambath for chest and back soreness; Mendocino Indians used plants as a substitute for lettuce. The Miwok boiled leaves for food; the Shoshoni applied a poultice of crushed leaves to wounds or rope burns; and the Yavapai took a decoction as tea for stomachache. These documented uses pertain to M. guttatus, not specifically to E. lewisii, and are presented here to illustrate genus-level patterns.
No peer-reviewed ethnobotanical sources located in the preparation of this article document specific, verifiable traditional medicinal or food uses of Erythranthe lewisii / Mimulus lewisii in isolation from other Mimulus species by any named indigenous group. The available scholarly ethnobotanical databases (notably the University of Michigan's Native American Ethnobotany database) record traditional uses for Mimulus species collectively, but specific attributed uses for M. lewisii itself are not confirmed in the sources accessed for this article. Claims of traditional medicinal use specifically attributed to E. lewisii should therefore be treated with caution unless they are supported by primary ethnobotanical records.
The most extensively documented use of Mimulus in the context of health and wellness supplements is within the Bach Flower Remedy system. Bach flower remedies (BFRs) are a widely available, popular form of complementary and alternative medicine (CAM) developed in the 1930s by the British physician Dr. Edward Bach. Bach devoted his life to the discovery of 38 remedies that correspond to 38 negative emotional states. It is important to note that the Mimulus used in the classic Bach system is Mimulus guttatus (yellow monkeyflower), not Mimulus lewisii. To prepare the Bach Flower Remedy, the yellow-hued M. guttatus is specified. Initially, Dr. Edward Bach named the yellow mimulus flowers as Mimulus luteus; they were later identified as Mimulus guttatus. Mimulus lewisii is not the primary species in classical Bach preparations, though the two species are often grouped under the single common name "monkeyflower" in popular literature, and some contemporary Bach preparations may draw from the broader genus.
In the Bach framework, Mimulus "is the remedy for known fears." Whenever a person is frightened or anxious about something that can be named, Mimulus is specified. Mimulus fears include everyday fears: fear of public speaking, of the dark, of aggressive dogs, of illness and pain. It is also used as a type or personality remedy for those who tend generally to be nervous, timid, and shy β who might blush easily or stammer, and avoid social occasions.
The flower essence remedy is prepared employing the sun method: the practitioner locates a place where the plant grows robustly in the wild beside a bright stream, collects flowers from many different plants, gathers them along with their stalks, floats them on water in a bowl, and places the bowl so the flowers on the surface are exposed to sunlight. Commercial Bach preparations contain flower extracts of Mimulus in grape alcohol (approximately 27% v/v).
The bumblebee-pollinated Mimulus lewisii bears pink flowers colored by anthocyanins (except the yellow nectar guides, which result from carotenoid pigmentation). Ten anthocyanins have been characterized from M. lewisii and M. cardinalis petal lobes by high-performance liquid chromatography (HPLC) and electrospray tandem mass spectrometry (ES/MSMS). Cyanidin biosides comprise 33% of all the anthocyanins in M. lewisii. Total anthocyanin concentration in the petals of M. cardinalis is approximately twice as high as that in M. lewisii, with the difference accounted for by the presence of two pelargonidin biosides, probably rhamnohexosides, unique to M. cardinalis.
The specific R2R3-MYB transcription factors controlling anthocyanin production in M. lewisii have been identified at the molecular level. Through transcriptome profiling, mutant analyses, and transgenic experiments, researchers have established a floral anthocyanin regulation model in Mimulus lewisii: one WD40 and one bHLH gene control anthocyanin pigmentation in the entire corolla, while two R2R3-MYB genes, PELAN and NEGAN, control anthocyanin production in the petal lobe and nectar guide, respectively.
Competition between anthocyanin and flavonol biosynthesis sets a "prepattern" of pigment distribution in M. lewisii, producing a white region surrounding the throat of the otherwise pink corolla. The absence of anthocyanins in the white areas surrounding the otherwise pink corolla of bumblebee-pollinated Mimulus lewisii flowers is due to high flavonol synthase (FLS) expression. An early study by Bohm (1992) reported on exudate flavonoids from Mimulus lewisii (cited as a reference within the broader Mimulus phytochemistry literature), documenting their presence in leaf surface exudates, though detailed structural characterization of those compounds is not elaborated in the primary sources reviewed here.
A study characterizing the floral carotenoid composition of 11 Mimulus species, using high-performance liquid chromatography, mass spectrometry, and chemical methods, identified five major carotenoids in M. lewisii flowers: antheraxanthin, violaxanthin, neoxanthin, and the unique allenic carotenoids deepoxyneoxanthin and mimulaxanthin. This carotenoid profile is consistent with the expression levels of putative carotenoid biosynthetic genes in the M. lewisii flower. The carotenoids found in Mimulus species are related to carotenes, which help attract pollinators and also protect the plant by acting as antioxidants. The presence of mimulaxanthin as a unique allenic pigment in M. lewisii flowers is notable from a phytochemical standpoint, though no pharmacological studies of this compound in isolation have been located in the literature reviewed.
Research on the broader monkeyflower genus has illuminated a class of secondary metabolites relevant across related species. Yellow monkeyflower (Mimulus guttatus) has long been a model plant species for studies in genetics, evolution, and ecology; nonetheless, exceedingly little was known about its secondary chemistry until recently. Researchers discovered that the foliage of yellow monkeyflower contains a diverse suite of phenylpropanoid glycosides (PPGs), a class of compounds with many known biological activities. Using 1H and 13C NMR and UV and MS chromatography techniques, investigators positively identified five PPGs from the leaves, four of which occur in other species and one of which was previously undescribed; UV and high-resolution tandem MS data putatively identified 11 additional foliar compounds as PPGs. These findings are relevant background to E. lewisii, but it should be noted that they were established specifically in M. guttatus; comparable detailed characterization of foliar secondary chemistry of E. lewisii specifically has not been reported in the peer-reviewed literature reviewed here.
Bohm (1992) described flavonoids from the leaf exudate of Mimulus lewisii, and both Lincoln and Walla (1986) and Hare (2002) found that the surface leaf resins of Mimulus aurantiacus contain a variety of geranylflavanones and an Ξ±-pyrone. These represent the earliest documented reports of distinct flavonoid compounds in the leaf exudate of M. lewisii specifically.
The most extensive published research on Erythranthe lewisii pertains to its role as a genetic model organism, specifically in studies of floral pigmentation and pollinator-driven speciation. Researchers have identified a causal gene underlying spatial pattern variation of floral pigments between Mimulus lewisii and Mimulus cardinalis, demonstrating that competition between anthocyanin and flavonol biosynthesis sets a "prepattern" of pigment distribution in M. lewisii, producing a white region surrounding the throat of the otherwise pink corolla. This work has generated insights into the genetic control of pigment biosynthesis pathways (anthocyanins, flavonols, carotenoids) at a molecular level. However, this research is conducted entirely within the domain of evolutionary genetics and plant biology; it addresses how M. lewisii makes pigments, not whether those pigments have effects in human health contexts.
Evidence strength: Strong as basic science on plant pigment biosynthesis; not applicable to human health outcomes.
The use of Mimulus flower preparations as a remedy for fear and anxiety β the primary context in which this plant appears in wellness and supplement commerce β belongs to the Bach Flower Remedy (BFR) tradition. The evidence for BFRs overall has been evaluated by multiple systematic reviews.
Bach flower remedies continue to be popular and proponents make a range of medicinal claims for them. A systematic review was conducted to critically evaluate the evidence for these claims: five electronic databases were searched without restrictions on time or language, and all randomised clinical trials of flower remedies were identified. Seven such studies were located. All but one were placebo-controlled. All placebo-controlled trials failed to demonstrate efficacy. It is concluded that the most reliable clinical trials do not show any differences between flower remedies and placebos.
A second systematic review, focused specifically on psychological problems and pain, reached consistent conclusions. The available evidence indicates that BFRs are not more efficacious than a placebo intervention for psychological problems but are probably safe. Due to a lack of methodologically sound trials, this statement is associated with a high level of uncertainty. Few controlled prospective trials of BFRs for psychological problems and pain exist. Analysis of the four controlled trials of BFRs for examination anxiety and ADHD indicates that there is no evidence of benefit compared with a placebo intervention.
The systematic review reveals that seven RCTs provide insufficient evidence for clinical efficacy, with most showing no significant differences from placebo. Methodological quality was evaluated using the Jadad scale, with scores ranging from 0 to 5; two studies achieved the maximum score. The review's limitations include potential publication bias and the risk of error due to data extraction being done by a single author.
Three RCTs of BFRs for students with examination anxiety, and one RCT of BFRs for children with attention-deficit hyperactivity disorder (ADHD), showed no overall benefit in comparison to placebo. Due to the number and quality of the studies, the strength of the evidence is low.
Although Mimulus is well established in traditional and holistic practices, robust scientific validation of its health benefits remains limited. Research specifically focusing on Mimulus extract in clinical settings is sparse, and most available evidence arises from anecdotal reports and observational studies related to Bach flower remedies as a whole.
Evidence strength for Bach Flower Remedy use: The clinical evidence is weak. Multiple placebo-controlled RCTs and two published systematic reviews uniformly conclude that Bach flower remedies, as a category, do not outperform placebo. No published RCTs have specifically tested a Mimulus lewisii-derived preparation as a distinct intervention. The FDA has explicitly stated that it is not aware of scientific evidence to support homeopathy as effective.
Carotenoids found in Mimulus species, related to carotenes, help attract pollinators and also protect the plant by acting as antioxidants. However, no human clinical studies investigating antioxidant effects of E. lewisii-specific preparations in humans have been identified in the scientific literature reviewed for this article. The characterization of antioxidant compounds such as carotenoids and flavonoids in the flowers is at the level of phytochemical identification, not clinical pharmacology.
Evidence strength for antioxidant claims: Preclinical/phytochemical only. No clinical data available for E. lewisii specifically.
A systematic search of the peer-reviewed literature (PubMed/PMC) reveals no published clinical trials evaluating Erythranthe lewisii or Mimulus lewisii for any specific human health endpoint β including but not limited to cardiovascular, metabolic, anti-inflammatory, antimicrobial, or neurological indications. No dosage-ranging studies, pharmacokinetic studies, or safety trials specific to this species have been published. The entirety of the human-context literature consists of studies of Bach flower remedies in which Mimulus (primarily M. guttatus) is used as part of a multi-ingredient or genus-level preparation.
The health areas with which Lewis's monkey flower and the broader Mimulus genus are associated in commerce and traditional systems are as follows. The strength of evidence for each is noted:
Lewis's monkey flower appears in commerce primarily as a Bach Flower Remedy preparation, not as an herbal extract, standardized botanical supplement, or isolated phytochemical product. The following dosages are those reported for commercial Bach Remedy preparations containing Mimulus (as Mimulus guttatus / generic Mimulus):
No dosage information derived from pharmacological or clinical studies specific to Erythranthe lewisii or its isolated constituents exists in the literature reviewed. There are no established therapeutic dosages for any standardized extract of this species.
The Bach Remedy preparations are ultra-dilute: the essence is prepared at a 1:240 "stock" strength, in strict accordance with the methods of Dr. Bach. At this extreme dilution, the amount of any active botanical molecule present is pharmacologically negligible.
Only four of the six studies included for safety in one systematic review explicitly reported adverse events. Most of the available evidence regarding the efficacy and safety of BFRs has a high risk of bias. Based on the reported adverse events in these six trials, BFRs are probably safe.
Two of the six studies reviewed for safety did not report on adverse events. One RCT and one case series reported that there were no adverse events. One RCT reported one adverse event (details not given). One RCT reported six adverse events β three in the Bach flower remedies group (headaches, skin eruptions) and three in the placebo group (vomiting, hay fever, and a depressive mood).
Most of the available evidence regarding the efficacy and safety of BFRs has a high risk of bias. Based on the reported adverse events in the available trials, BFRs are probably safe. Due to a lack of methodologically sound trials, this statement is associated with a high level of uncertainty.
Commercial Bach Remedy preparations contain flower extracts of Mimulus in grape alcohol (approximately 27% v/v). Alternative preparations use brandy as a preservative, at 40% alcohol by volume. This alcohol content is relevant for individuals who must avoid alcohol for medical, religious, or recovery reasons, and for use in children and pregnant or breastfeeding individuals.
No specific toxicological studies of Erythranthe lewisii or its isolated constituents (carotenoids, anthocyanins, flavonols) have been identified in the peer-reviewed literature reviewed. The ultra-dilute nature of Bach Flower preparations means that phytochemical toxicity from the plant per se is highly unlikely in those commercial formats. For direct use of plant material (e.g., as a raw herb or concentrated extract), no safety data exist in human populations based on the literature reviewed.
No published data on pharmacokinetic or pharmacodynamic drug interactions involving Erythranthe lewisii preparations were found in any source reviewed. Given the ultra-dilute nature of Bach Remedy preparations and the near-complete absence of pharmacological research on the species, no interaction claims can be substantiated from current evidence.
The U.S. FDA is not aware of scientific evidence to support homeopathy as effective. Bach Original Flower Remedies Mimulus products are listed on the FDA's DailyMed database, with the active ingredient indicated as per the Homeopathic Pharmacopoeia of the United States (HPUS). This listing denotes classification as a homeopathic product, not regulatory approval of efficacy.
The following gaps in the evidence base are important to note for any evaluative purpose:
Health conditions that Lewis's monkey flower may help support.
Body systems that Lewis's monkey flower may help support.
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