Montana Field Guide

Plants: Annual with erect stems, 5-50 cm, branched above (Lesica 2012) rather rigidly and diffusely, conspicuously striate-angled (Hitchcock et al. 1961); herbage smooth throughout or minutely pubescent near the base (McGregor et al. 1986).

Leaves: Alternate, near-opposite below, linear or narrowly lanceolate, entire or higher ones with a few teeth, up to 4 mm in width (McGregor et al. 1986) and 10-30 mm in length; bracts awned, glandular-serrate, sometimes with small, purple stipular glands (Lesica 2012).

Inflorescence: A leafy-bracteate, often flat-topped panicle (Lesica 2012).

In Montana two varieties occur; however, they reproductively intergrade and cannot be separated by geography or ecology (Lesica 2012).

Linum rigidum var. compactum: Plants are 20 cm or less in height (Lesica 2012), sometimes up to 32 cm (McGregor et al. 1986) and lack glands on the stipules (Lesica 2012).

Linum rigidum var. rigidum: Plants are 20 cm or more in height (Lesica 2012), as much as 40 cm with ascending branches (McGregor et al. 1986), and possess glands on the stipules (Lesica 2012).


(Lesica's contribution adapted from Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX)

Variety compactum: Flowers May – September (McGregor et al. 1986).

Variety rigidium: Flowers May-October (McGregor et al. 1986).

Plants of variety rigidum are 20 cm or more in height, have styles 4-6 mm in length, and possess stipular glands. Variety compactum plants are 20 cm or less in height, have styles 3-4 mm in length, and lack stipular glands (Lesica 2012).

The two varieties may be difficult to separate in the northern Great Plains where style length may be similar and lower leaves of variety compactum plants occasionally possess stipular glands (McGregor et al. 1986).

(Lesica’s contribution adapted from Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX)

Linum rigidum: Grasslands, sagebrush steppe; plains, valleys (Lesica 2012).

Variety compactum: Pebbly or sandy prairies, high plains (McGregor et al. 1986).

Variety rigidum: Sparsely or moderately wooded hillsides, sandy prairies, rarely in grasslands with high calcium content (McGregor et al. 1986).

(Lesica’s contribution adapted from Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX)

Linum rigidum var. rigidum and L. rigidum var. compactum intergrade (Rogers 1968) and are similar ecologically and geographically in MT (Lesica 2012).

(Lesica's contribution adapted from Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

POLLINATORS
The following animal species have been reported as pollinators of this plant species or its genus where their geographic ranges overlap: Bombus bifarius (Thorp et al. 1983).

Flowers: Flowers yellow; sepals lanceolate, 5-9 mm in length, glandular-serrate (Lesica 2012), 1- or 3-veined; petals yellow, often reddish and hairy at the base, ovate or widely so (McGregor et al. 1986), 7-16 mm in length; style 3-6 mm in length, united to above the middle (Lesica 2012); stamens (4)6-8(9) mm in length, with anthers elliptic or linear-elliptic (McGregor et al. 1986).

Fruit: The deltoid-ovate capsule 2.5-3.5(4) mm in width (McGregor et al. 1986), 4-5 mm in length, splitting into 5 2-seeded segments (Lesica 2012); seeds brownish, ca 3 mm in length and 1.0-1.5 mm in width (McGregor et al. 1986).

Var. compactum: Plants have styles 3-4 mm in length (Lesica 2012), and more or less ovate fruits with russet seeds (McGregor et al. 1986).

Var. rigidum: Plants have styles mostly 4-6 mm in length (Lesica 2012), sometimes as much as 11 mm, and oval, lustrous fruits with brown seeds (McGregor et al. 1986).

(Lesica’s contribution adapted from Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX)