Montana Field Guide

PLANTS: Herbaceous perennial plants that grow from bulbs. Stems are usually single and 40-60 cm tall. Source: Lesica et al. 2012.

LEAVES: Few, basal and alternately arranged on stem. Basal leaves are linear, about 5 mm wide, channeled, and usually shorter than stem leaves. Sources: Lesica et al. 2012; Giblin et al. [eds.] 2018.

INFLORESCENCE: Terminal, of 1 to 4 stemmed (pedicellate), purplish flowers. Bracts are 2-4 cm long. 3 sepals alternate with 3 petals. Sepals are narrow, often shorter than petals, purplish as their base, and 1-4 cm long. Petals are white, apiculate, and 2-4 cm long; outer surface with a green midvein; inner surface glabrous with a dark, crescent-shape above the small, circular gland. Sources: Lesica et al. 2012; Giblin et al. [eds.] 2018.

The genus, Calochortus, comes from the Greek words kalos meaning 'beautiful' and chortos meaning 'grass' (Fiedler and Zebell in FNA 2002).

Flowering in July in Montana. Across its range flowering occurs from late spring to summer (Fiedler and Zebell in FNA 2002).

Of Montana's 7 Calochortus species, Calochortus nuttallii is most likely to be mis-identified as Calochortus bruneaunis.

Bruneau Mariposa Lily - Calochortus bruneaunis, SOC
*Basal Leaf: Channeled, similar in width, but shorter than stem leaves.
*Anthers: Oblong and blunt-tipped.
*Sepals: Usually shorter than petals.
*Petals: White. Green striped on the outside. Nearly hairless on the inside (glabrate) near gland. Tip apiculate.

Nuttall's Mariposa Lily - Calochortus nuttallii
*Basal Leaf: Channeled, similar in width, but shorter than stem leaves.
*Anthers: Oblong.
*Sepals: Longer or shorter than petals.
*Petals: White to purple tinged, yellow at the base. Lacking a green stripe on the outside. Bearded on the inside, adjacent to gland. Tip apiculate.

Green-band Mariposa Lily - Calochortus macrocarpus
*Basal Leaf: Channeled, similar in width, but shorter than stem leaves.
*Anthers: Lanceoloid (round in cross-section; wider from base to below middle then tapering to the tip).
*Sepals: Usually longer than petals.
*Petals: Purple. Green striped on the outside. Tip acuminate.

Gunnison's Mariposa Lily - Calochortus gunnisonii
*Basal Leaf: Channeled, similar in width, but shorter than stem leaves.
*Anthers: Apiculate (short, sharp tip).
*Sepals: Usually shorter than petals.
*Petals: White or yellowish to purple; greenish inside and sometimes purple-banded or -spotted next to gland. Green stripe absent on the outside. Tip not acuminate.

The following Mariposa Lilies differ from those above in that their basal leaves are flat, much wider than the stem leaves, and often more than half as long as the stem leaves:
Baker Mariposa Lily - Calochortus apiculatus
Elegant Mariposa Lily - Calochortus elegans
Big-pod Mariposa Lily - Calochortus eurycarpus

Across it range plants are found in dry brush, grassy slopes, flats, pinyon-juniper woodlands from 900-3000 meters (Fiedler and Zebell in FNA 2002).

Sagebrush steppe in the montane zone of Montana (Lesica et al. 2012).

At two Montana sites plants grow on steep, less vegetated, and somewhat rocky slopes (Andrea Pipp personal communication). Plants were not found in draws which have higher soil moisture or on flatter ridgetops. Habitat is dominated by grasses, shrubs, and/or forbs. Associated plants included Antennaria sp. Artemisia frigida, Artemisia tridentata ssp. tridentata, Balsamorhiza sagittata, Elymus spicatus, Eriogonum sp., Gaura coccinea, Gutierrezia sarothrae, Heuchera parvifolia, Festuca idahoensis, Leptodactylon pungens, Lewisia rediviva, Opuntia polyacantha, Selaginella sp., Stipa comata, and Stipa viridula. The biological soil crust community is prevalent and diverse; Xanthoparmelia species are very common.

For Calochortus, petal size can vary between years and may be associated with soil moisture (Lesica et al. 2012).

Plants reproduce from seed.

PROPAGATION
Most species propagate easily from seeds (Giblin et al. [eds.] 2018). It takes from 3-5 years to grow from seed to a flowering bulb (Giblin et al. [eds.] 2018). Bulbs collected in the wild rarely survive when planted (Giblin et al. [eds.] 2018).

FLOWERS
Petals: 3, distinct, white with a green midvein (outside), and white with a red-purple spot above the gland (inside). At the base of the petal is the gland.
Gland: Circular, yellow, and glabrous or with a few, short, thick hairs nearby.
Stamens: 6, anthers are oblong, blunt-tipped, and often shorter than the filaments.
Pistil: Single with a 3-lobed style.

FRUITS
Fruit is a capsule. Capsule is spindle-shaped, erect, 3-7 cm long, and filled with many seeds. Ovary and capsules elongate greatly with age (longer than thick) and are not winged (Giblin et al. [eds.] 2018).

GRAZING
At one site plants occur within a grazing allotment managed by the BLM using a rest-rotation system. Signs of livestock use appeared to be less on the steep slopes where Bruneau Mariposa Lily plants were common (Andrea Pipp personal communication). Likewise, signs of livestock use seemed more prevalent on the flatter slopes where plants were rarely observed (Andrea Pipp personal communication). Studies or monitoring that examine the interaction between livestock grazing and Bruneau Mariposa Lily population ecology is needed.

Plants are threatened by the invasion of exotic plants, particularly Cheatgrass (Bromus tectorum) which colonizes naturally open ground.

STATE THREAT SCORE REASON
Reported threats to Montana's populations of Bruneau Mariposa Lily are due to invasive species and roads found at populations. Cheatgrass (Bromus tectorum) and Yellow Sweetclover (Melilotus officinalis) are colonizing existing populations, and are spreading along a two-track road that is exposed to an interstate highway. Evidence of livestock use in previous years was also found at one population, but related impacts to Bruneau Mariposa Lily plant or populations could not be determined (MTNHP Threat Assessment 2021).