Bryophytes of Santa Barbara

Grimmia laevigata (Bridel) Bridel

Grimmia laevigata is a medium-sized (0.5-2 cm high), sparsely branched, acrocarpous moss, with long white hair points on the leaves, which lend it a distinctive hoary look. The plants grow in tight rounded mounds or flattened islands, appearing whitish grey when dry, and whitish light green when moist. It is common on rocks and boulders in full sun to dappled shade.

Scroll down for more photos (click to enlarge) and descriptions of habitat, plants, leaves, sporophytes, distribution map, name origin, and similar species.

Grimmia laevigata — Grimmia laevigata, dry, on top of large boulder (CAH #941). CC BY-NC Amanda Heinrich

Habitat: Grimmia laevigata grows on rocks and boulders in full sun to dappled shade.

Grimmia laevigata — Grimmia laevigata on large sandstone boulder in full sun, moist (CAH #1076). CC BY-NC Amanda Heinrich

Grimmia laevigata — Grimmia laevigata on large sandstone boulder in full sun, dry (CAH #1076). CC BY-NC Amanda Heinrich

Grimmia laevigata — Grimmia laevigata on large sandstone boulder in full sun, moist (CAH #126). CC BY-NC Amanda Heinrich

Grimmia laevigata — Grimmia laevigata on large sandstone boulder in full sun, dry (CAH #126). CC BY-NC Amanda Heinrich

Grimmia laevigata — Grimmia laevigata (left of penny) on large sandstone boulder, in dappled shade with other moss species, all moist (CAH #941). CC BY-NC Amanda Heinrich

Grimmia laevigata — Grimmia laevigata (surrounding penny) on large sandstone boulder, in dappled shade with other moss species, all dry (CAH #941). CC BY-NC Amanda Heinrich

Habit: Grimmia laevigata grows in tufts which may resemble rounded mounds or flattened islands. Plants are generally packed tightly together, but disassociate readily from the clump when collected, a hallmark feature.

Grimmia laevigata — Grimmia laevigata moist islands, light green with a dusting of white (CAH #1076). CC BY-NC Amanda Heinrich

Grimmia laevigata — Grimmia laevigata dry islands, dark gray with a white frost (CAH #1076). CC BY-NC Amanda Heinrich

Grimmia laevigata — Grimmia laevigata moist mounds, light green with a dusting of white, surrounded here by other moss species lacking white leaf tips (CAH #941). CC BY-NC Amanda Heinrich

Grimmia laevigata — Grimmia laevigata dry mounds, dark gray with a white frost (CAH #941). CC BY-NC Amanda Heinrich

Plants: Grimmia laevigata plants are 0.5-2 cm high and sparsely branched. The leaves are light olive-green with long white awns when moist, and are held quite stiffly away from the stem. When dry, the leaves become a much darker shade of olive-green/brown, and are appressed tightly to the stem, overlapping neatly like scales, and accentuating the white awns.

Grimmia laevigata — Grimmia laevigata moist plants, leaves light olive green to brown with long white awns, outstretched from stem (CAH #126). CC BY-NC Amanda Heinrich

Grimmia laevigata — Grimmia laevigata dry plants, leaves darker olive green to brown with long white awns, appressed to stem and neatly overlapping (CAH #941). CC BY-NC Amanda Heinrich

Grimmia laevigata — Grimmia laevigata moist plants, leaves light olive green to brown with long white awns, outstretched from stem (CAH #1076). CC BY-NC Amanda Heinrich

Grimmia laevigata plants moist — Grimmia laevigata plants moist (CAH #1076). CC BY-NC Amanda Heinrich

Grimmia laevigata plants dry — Grimmia laevigata plants dry (CAH #1076). CC BY-NC Amanda Heinrich

Leaves: Grimmia laevigata leaves are 1.5-3 mm long, concave, and oblong with a flared, ovate base. The long (0.3-2 mm) hyaline awns (colorless leaf points) are covered with spines and are decurrent, that is the edges creep down the sides of the leaf. The upper portion of the leaf is bistratose (two cells thick) whereas the lower portion is merely unistratose. The costa (midrib) is very broad at the base of the leaf, and only a few cells thick when viewed in cross-section. The cells of the leaf base are often wider than long, and have thick transverse walls and thin longitudinal walls.

Grimmia laevigata leaf — Grimmia laevigata oblong-ovate leaf with long hyaline awn and wide costa at base (CAH #1076). CC BY-NC Amanda Heinrich

Grimmia laevigata awn — Grimmia laevigata hyaline, spinose, decurrent awn (CAH #1076). CC BY-NC Amanda Heinrich

Grimmia laevigata bistratose leaf cross-section — Grimmia laevigata bistratose upper leaf cross-section (CAH #1076). CC BY-NC Amanda Heinrich

Grimmia laevigata costa cross-section — Grimmia laevigata leaf base cross-section, showing broad but thin costa flanked by unistratose lamina (CAH #1076). CC BY-NC Amanda Heinrich

Grimmia laevigata basal leaf cells — Grimmia laevigata basal leaf cells, often wider than high, with thick transverse walls and thin lateral walls (CAH #1076). CC BY-NC Amanda Heinrich

Sporophytes: Sporophytes are rather rare on Grimmia laevigata. The oblong capsule is held atop a short seta, and capped with a split (mitrate) calyptra.

Grimmia laevigata — Grimmia laevigata with rare sporophytes. CC BY-NC Amanda Heinrich

Distribution: Grimmia laevigata is found on every continent except Antarctica. It is common throughout California, including in Santa Barbara County.

Grimmia laevigata distribution map — Grimmia laevigata collections. Map generated by google maps using data from the Consortium of Bryophyte Herbaria of accessioned collections from herbaria.

Similar Species in Santa Barbara County: Hedwigia detonsa and Hedwigia stellata have a similar hoary look, but are much longer and lankier.

Name: The genus Grimmia, is named for J.F.K. Grimm, a German botanist and physician, who lived from 1737 to 1821.

laevigata is Latin for smoothed or polished, perhaps a reference to the scaly appearance of the dry, overlapping leaves, or possibly the super smooth sporophyte capsules.

References and Further Reading

Grimmia laevigata, Roxanne I. Hastings, Henk C. Greven, Flora of North America Vol. 27, www.efloras.org

California Mosses, Bill and Nancy Malcolm, Jim Shevock and Dan Norris. Available for purchase from the California Native Plant Society here.

Contributions toward a Bryoflora of California II. A Key to the Mosses, Daniel H. Norris and James R. Shevock, Madrono 51(2): 133-269. 2004. Available for purchase here.

Grimmia laevigata, British Bryological Society Field Guide

Grimmia laevigata, Plants of the Gila Wilderness

The Moss Flora of Mexico, Edited by Aaron J. Sharp, Howard Crum & Patricia M Eckel, The New York Botanical Garden, 1994

Grimmia laevigata, Bildatlas der Moose Deutschlands, Michael Lüth