Flora of the Great Plains (McGregor et al. 1986), Allred and Ivey 2012, VPAP (Wilken and Porter 2005)

Duration: Perenial Nativity: Native Lifeform: Forb/Herb General: Suffrutescent perennial herb, sometimes blooming in the first year, 8-25 cm tall; stems diffusely branched from the base, glandular-puberulent. Leaves: Alternate and crowded along the stems; blades pinnatifid to pinnate, 6-25 mm long, unequally divided into 2-7 acerose (needle-like) to linear-oblong segments, these 2-12 mm long, tipped with short, abrupt points, and covered with tiny gland-tipped hairs. Flowers: Blue and yellow, solitary or in loose clusters near branch tips; calyx cylindrical or ovoid, 2-5 mm long, consisting of 5 herbaceous, gland-covered sepals connected to each other by papery membranes; corolla rotate and 5-lobed, the tube 3-4 mm long, about the same length as the calyx, the lobes 3-5 mm long, round or oval; corolla color is blue-violet to purple, with a yellow throat; stamens exserted beyond the corolla. Fruits: Capsules 3-5 mm long, globose to ovoid; containing several seeds. Ecology: Found on dry rocky to sandy substrates, in juniper woodlands, grasslands, desertscrub, and gypsum soils, below 6,500 ft (1981 m); flowers April-August. Distribution: CO and KS, south to OK, TX, NM and AZ; south to MEX. Notes: This low, slightly woody perennial is inconspicuous when not in flower, with its dense short needle-like leaves. The flowers are showy and bell-shaped, blue with yellow inside the throat. It resembles Phlox austromontana, but that species is woodier at the base and much longer-lived, as evidenced by the copuous grayish-colored dead leaves that persist on the lower parts of the branches. P. austromontana also has pale lavender or white flowers with corollas 8-18 mm long, about three times the size of G. rigidulum's much darker blue flowers. Most closely related to G. acerosum, which only has acerose (needle-like) leaves; G. rigidulum has acerose upper leaves and lower leaves with slightly broader segments. Until recently, G. acerosum was treated as a subspecies of G. rigidulum. Ethnobotany: The crushed plant used to massage the muscles for cramps. Etymology: Giliastrum means resembling Gilia, the genus to which this plant once belonged; rigidulum refers to the rigid leaves. Editor: AHazelton 2017