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Montana Field Guides

Stalk-leaved Monkeyflower - Mimulus ampliatus
Other Names:  Mimulus patulus, Mimulus washingtonensis

Species of Concern
Native Species

Global Rank: G3
State Rank: S3
(see State Rank Reason below)

Agency Status
C-value: 7


External Links

State Rank Reason (see State Rank above)
See rank details.
  • Details on Status Ranking and Review
    Stalk-leaved Monkeyflower (Mimulus ampliatus) Conservation Status Review
    Review Date = 04/01/2013
    View State Conservation Rank Criteria
    Population Size

    Score1-2 - Small to Moderate. Population size is imprecisely known but is believed to be >2,000 individuals and <100,000 individuals.

    CommentPopulation levels are poorly documented and likely fluctuate widely from year to year.

    Range Extent

    Score2 - Regional or State Endemic or Small Montana Range: Generally restricted to an area <100,000 sq. miles (equivalent to 2/3 the size of Montana or less) or Montana contributes 50% or more of the species’ range or populations OR limited to 2-3 Sub-basins in Montana.

    Area of Occupancy

    Score1 - Moderate: Generally occurring in 11-25 Subwatersheds (6th Code HUC’s).

    Environmental Specificity

    Score1 - Moderate: Species is restricted to a specific habitat that is more widely distributed or to several restricted habitats and is typically dependent upon relatively unaltered, good-quality habitat (C Values of 5-7).


    ScoreNA - Rank factor not assessed.

    CommentTrends are unknown, though there is no indication that the species' has experienced severe declines in Montana.


    Score0-1 - Low to Medium.

    CommentSome occurrences are near areas of human-use and have the potential to be negatively impacted. However, no threats have been identified that would be high in terms of scope or severity.

    Intrinsic Vulnerability

    Score1 - Moderate Vulnerability: Specific biological attributes, unusual life history characteristics or limited reproductive potential makes the species susceptible to extirpation from stochastic events or other adverse impacts to its habitat and slow to recover.

    Raw Conservation Status Score

    Score 6 to 8 total points scored out of a possible 16 (Rarity factors and threats only).

General Description
PLANTS: An annual that has erect stems and grows from 2 to 12 cm tall (Lesica et al. 2012). Plants are nearly hairless (glabrate) to glandular-puberulent. Plants are fibrous rooted or have a slender taproot. Sources: Giblin et al. [eds.] 2018; Lesica et al. 2012.

LEAVES: Leaves are simple, sessile, and arranged opposite on the stem. The leaf petiole is generally less than or equal to the length of the blade, about 2-10 mm long. Source: Lesica et al. 2012.

INFLORESCENCE: Showy yellow flowers grow on long stems (pedicels) from the upper leaf axils. Flowers are strongly bilabiate, petals flare open, and lowest petal is the longest. Source: Giblin et al. [eds.] 2018; Lesica et al. 2012.

The specific epithet ampliatus translates from Latin to “expanded” in reference to its expanded lower lip (Merriam-Webster 2019). Mimulus is derived from the Latin word mime, meaning “actor” or “mimic,” and the male diminutive -ulus (Merriam-Webster 2019). This is most likely referring to the mask-like appearance of the flowers.

Stalk-leaved Monkeyflower flowers in late June and early July (Nesom et al. 2012).

Diagnostic Characteristics
Montana specimens of Mimulus ampliatus have previously been incorrectly referred to as Mimulus patulus or Mimulus washingtonensis which do not occur in Montana (Lesica et al. 2012). Many past reports of M. floribundus were mis-identified and are actually Mimulus ampliatus.

Montana has 14 native Mimulus species (Lesica et al. 2012). The following species share characteristics of being short annuals, often less than 15 cm tall, with yellow flowers.

Stalk-leaved Monkeyflower-Mimulus ampliatus
*Hairs: Stems and calyx glabrate to glandular pubescent. Hairs are single-celled (not septate).
*Leaves: Petiolate. Blades are ovate, dentate, 2-10 mm long.
*Flower Stem: Pedicel is 2-3 times as long as the calyx.
*Corolla: 10-15 mm long, yellow, flares open, strongly bilabiate, and lower lip is longest.
*Calyx: Purplish, 4-8 mm long. Teeth (or lobes) equal, about 0.5 mm long.

Short-flowered Monkeyflower-Mimulus breviflorus
*Hairs: Stems and calyx with glandular-puberulent. Hairs are single-celled (not septate).
*Leaves: Petiolate, usually longer than the calyx. Blades are narrowly elliptic, entire, and 5-10 mm long.
*Flower Stem: Pedicel is 1-3 times as long as the calyx.
*Corolla: 5-8 mm long, yellow, and slightly bilabiate with subequal lobes.
*Calyx: 3-5 mm long. Teeth about equal, 1 mm or less long.

Floriferous Monkeyflower-Mimulus floribundus
*Hairs: Stems and calyx with glandular-villous, usually multi-cellular (septate), but occasionally unicellular hairs.
*Leaves: Petiolate, mostly shorter than the leaf blades. Blades are ovate, not noticeably dentate, and 4-12 mm long.
*Flower Stem: In fruit the pedicel ascends or is curved, and is not pressed against the substrate.
*Corolla: 7-11 mm long, yellow, bilabiate with a larger lower lobe and a red-spotted palate.
*Calyx: 4-7 mm long. Teeth equal, 1 mm or less long.

Thinsepal Monkeyflower-Mimulus hymenophyllus
*Stems are generally more prostrate and at the basal nodes are sharply bent.
*Hairs: Stems and calyx with sparsely glandular-pubescent. Hairs are single-celled (not septate).
*Leaves: Long-petiolate. Petiole is mostly longer than the blade. Blades are ovate, dentate, and 4-12 mm long.
*Flower Stem: Pedicel of flower is 3-4 times longer than the calyx. In fruit the pedicel bends to form about a 90-degree angle with stem and is generally pressed against the substrate.
*Corolla: 7-20 mm long, yellow, and nearly regular.
*Calyx: 3-5 mmm long. Teeth about equal with rounded to ovate tips. About 1 mm long.

Short-flowered Monkeyflower-Mimulus suksdorfii
*Hairs: Stems and calyx glabrate to glandular-puberulent. Hairs are single-celled (not septate).
*Leaves: Sessile. Blades are narrowly elliptic, entire, and 5-10 mm long.
*Flower Stems: Calyx about as long as the pedicel.
*Corolla: 5-8 mm long, yellow, and slightly bilabiate with subequal lobes.
*Calyx: Purplish, 3-5 mm long. Teeth about equal, 0.5 mm or less long.
*Habitat: In drier habitats than most Monkeyflowers.

Common Large Monkeyflower-Mimulus guttatus
*Plants found in temporarily moist areas, may grow as short annuals while those in permanently moist areas tend to be taller perennials; Sometimes plants become stoloniferous (Lesica et al. 2012).
*Hairs: Stems and calyx glabrate to glandular-puberulent. Hairs are single-celled (not septate).
*Leaves: Petiole is short. Blades are ovate, serrate, and 0.5-9 cm long.
*Corolla: 15-40 mm long, yellow with red-spots, and strongly bilabiate with spreading lips.
*Calyx: 6-14 mm long. Teeth (or lobes) acute, 0.5-3 mm long, and unequal; the upper calyx lobe is largest.

Species Range
Montana Range


Range Comments
Stalk-leaved Monkeyflower is endemic to central Idaho and western Montana (Lesica et al. 2012).

Observations in Montana Natural Heritage Program Database
Number of Observations: 37

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)

Stalk-leaved Monkeyflower prefers open seeps and vernally moist soil along slopes, cliffs and streams from the valleys to the subalpine zones in Montana (Lesica et al. 2012).
Predicted Suitable Habitat Model

This species has a Predicted Suitable Habitat Model available.

To learn how these Models were created see

In the Pacific Northwest, Stalk-leaved Monkeyflower can be found in Ponderosa Pine (Pinus ponderosa) grasslands as well as commonly among Bluebunch Wheatgrass (Elymus spicatus) and Idaho Fescue (Festuca idahoensis) (Meinke 1995). Populations have also been found associated with Wiregrass (Ventenata dubia) (Meinke 1992).

Based on its similarity to Mimulus washingtonensis it is presumed that Stalk-leaved Monkeyflower is pollinated by small, native, ground-nesting bees and bumblebees (Meinke 1995).

The following animal species have been reported as pollinators of this plant species or its genus where their geographic ranges overlap: Bombus vagans, Bombus bifarius, Bombus centralis, Bombus flavifrons, and Bombus pensylvanicus (Thorp et al. 1983, Colla and Dumesh 2010).

Reproductive Characteristics
Mature flowers of Stalk-leaved Monkeyflower have a 10 to 15 mm long yellow corolla that is bilabiate with a longer lower lip that is slightly deflexed from the upper (Lesica et al. 2012). The calyx is purplish and 4 to 8 mm long. The pedicel is 2 to 3 times as long as the calyx.

Mature fruit of Stalk-leaved Monkeyflower are ellipsoidal capsules, 3-6 mm long with many seeds (Lesica et al. 2012).

Threats or Limiting Factors
Across its range, it is presumed that Stalk-leaved Monkeyflower is sensitive to invasions by exotic grasses, particularly bromes (Bromus spp.) as well as presence of livestock (Meinke 1995). Individuals also are limited in their distribution by their dependence on a source of vernal moisture such as springs or seepages (Meinke 1995).

Threat impact not assigned because threats are not known.

  • Literature Cited AboveLegend:   View Online Publication
    • Colla, S.R. and S. Dumesh. 2010. The bumble bees of southern Ontario: notes on natural history and distribution. Journal of the Entomological Society of Ontario 141: 39-68.
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
    • Thorp, R.W., D.S. Horning, and L.L. Dunning. 1983. Bumble bees and cuckoo bumble bees of California (Hymenoptera: Apidae). Bulletin of the California Insect Survey 23:1-79.
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Citation for data on this website:
Stalk-leaved Monkeyflower — Mimulus ampliatus.  Montana Field Guide.  .  Retrieved on , from