Montana Field Guide

PLANTS: A slender, shallowly, fibrous-rooted annual that has erect stems and grows from 3 to 8 cm tall. Plants have glandular-puberulent hairs. Source: Lesica et al. 2012.

LEAVES: Leaves are simple, sessile, and arranged opposite on the stem. Leaves have petioles and blades are narrowly elliptic with entire margins and 2 to 10 mm long. Source: Lesica et al. 2012.

INFLORESCENCE: Yellow flowers that grow on long stems (pedicels) from the upper leaf axils.

The specific epithet breviflorus is a combination of the latin word brevis, meaning “short” or “slender,” and the root word flos, meaning flower. Mimulus is derived from the Latin word mime, meaning “actor” or “mimic,” and the male diminutive -ulus (Merrium-Webster 2019). This is most likely referring to the mask-like appearance of the flowers.

Short-flowered Monkeyflower flowers from late May through July (Nesom et al. 2012).

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.

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.

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.

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.

Short-flowered Monkeyflower prefers shallow, vernally moist soil among rock outcrops in coniferous forests or grasslands in the montane zone of Montana (Lesica et al. 2012).

POLLINATORS
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).

FLOWERS
The mature flowers of Short-flowered Monkeyflower have a 5 to 8 mm long, yellow corolla that is slightly bilabiate with subequal lobes (Lesica et al. 2012). The calyx is 3 to 5 mm long with equal length teeth that are up to 1 mm long. The pedicel is 1 to 3 times as long as the calyx.

FRUIT
Plants easily self-pollinate (Meinke 1992). Mature fruit are ellipsoidal capsules, 5-6 mm long, containing many seeds (Lesica et al. 2012).

Short-flowered Monkeyflower is able to control seed dormancy and seedling growth which allows it to survive in unpredictable environments (Meinke 1991). In late summer, seeds will develop partial or complete dormancy before capsules dehisce. Seeds released from their capsules and will germinate and continue growth only after several weeks of cold, wet conditions. In drought conditions, Short-flowered Monkeyflower seedlings exhibit accelerated sexual maturation and reproduction.

ALBINISM
Short-flowered Monkeyflower may exist in an albino form (Grant 1924). A collection made in 1914 with white flowers was unrecognized at the time and deemed Mimulus albus. However, M. albus continues to be an unrecognized species and this collection was later assumed to be an albino form of Short-flowered Monkeyflower or another closely related species.

Short-flowered Monkeyflower is one of the few annual species to be found in the dry, herb-dominated meadows (Meinke 1995). Its presence, as opposed to exotic annuals, may be used as a bioindicator to indicate relatively healthy conditions (Meinke 1995).

STATE THREAT SCORE REASON
Reported threats to Montana's populations of Short-flowered Monkeyflower indicate potential impacts due to hiking recreation and non-native plants (MTNHP Threat Assessment 2021). Trampling by hikers was reported to have negligible negative impacts at one population. Spotted Knapweed (Centaurea stoebe) and Cheatgrass (Bromus tectorum) were established at another population, but the severity of negative impacts is not known. Information on the scope, severity, and/or timing of threats to Short-flowered Monkeyflower are needed to assess its relative risk from threats.