Family HYLOCOMIACEAE

Common name

BENT-LEAF MOSS

Microhabitat

This moss is common in disturbed habitats, such as yards and roadsides. It was found among the grass at the eastern trailhead of Tatlow Trail. This species is a common lawn weed in the Pacific Northwest. It is also sometimes found on wet grassy slopes or stable sandy beaches near the ocean.

Distribution

R. squarrosus is circumpolar in the Northern Hemisphere, found predominantly in coastal areas but also in the mountains. On the west coast, this species is found from Alaska to northern California and inland to western Montana. It is uncommon in the boreal forest and the Rockies.

Close-up showing leaves on branches
Photo Credit: Yan Zhuang

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Morphology

Plants are relatively large and unbranched to irregularly branched. The main stems often stand erect to form extensive mats up to 15 cm high. Leaves are generally squarrose, meaning they bend down (or back) approximately halfway to the tip and spread at right angles from the stem. This leaf characteristic is maintained whether the plants are moist or dry and gives the plants a bristly appearance. Shoot tips are star-shaped when viewed from above. Individual leaves are 2.5-3.2 mm long, heart-shaped, sharply pointed and non-plicate (not folded or pleated longitudinally). No paraphyllia (small green filaments) are present along the stem.

Sporophytes are uncommon, but when present, are red-brown and upright with long stalks and short, smooth, horizontal capsules. Sporophytes originate from the side of the stem. They mature in spring and summer.

Key identifying features

The shoots of this moss resemble bunches of short pipecleaners, standing like miniature forests in most shady lawns. The uniquely squarrose leaves and erect unbranched main stems forming springy mats are distinguishing features. Other mosses found in similar habitats are generally non-squarrose. (Campylium spp. have squarrose leaves and are found in our region but are uncommon and restricted to rich fen habitats.) R. squarrosus can be distinguished easily from other species within the genus broadly by habitat: R. loreus and R. triquetrus are generally found in forested habitats. Furthermore, R. loreus has pleated leaves while R. squarrosus leaves are not pleated. Also, mats of R. squarrosus appear tidy when compared with the more unkempt look of R. triquetrus.

Interesting notes

This moss has a split personality. In Ireland, it is considered to provide high cover value as part of native bog woodlands. Here in the Pacific Northwest, it is a native species that is largely a lawn weed. In New Zealand, it is an exotic species that has been slowly spreading throughout the country for over 25 years.

Enhanced by late season mowing and fertilization, this moss grows throughout the winter while the grass lies dormant. A recent experiment showed that the cover of R. squarrosus increased with increasing cover of some grass species indicating the growth of the moss is also facilitated by the grasses. This moss has also been shown to be positively affected by sheep grazing in pasture land in Great Britain.

As with other mosses, this moss has been well-studied for its abilities to take up and accumulate high concentrations of heavy metals within its tissues, such as lead and cadmium. This process is often called bioaccumulation. Thus, this species may have potential both as a means of monitoring airborne and soil heavy metal pollution and for cleaning up contaminated sites.

Selected References

Hulme, P.D., Pakeman, R. J., Torvell, L., Fisher, J.M., and Gordon, I.J. 1999. The effects of controlled sheep grazing on the dynamics of upland Agrostis-Festuca grassland. J. Appl. Ecol. 36: 886-900.

Ingerpuu, N., Liira, J., and Partel, M. 2005. Vascular plants facilitated bryophytes in a grassland experiment. Plant Ecol. 180: 69-75.

Pojar, J., and MacKinnon, A. 1994. Plants of Coastal British Columbia. BC Ministry of Forests and Lone Pine Publishing, Vancouver, Canada.

Schofield, W.B. 1992. Some common mosses of British Columbia, 2nd ed. Royal British Columbia Museum, Victoria, Canada.

Vitt, D.H., Marsh, J.E., and Bovey, R.B. 1988. Mosses, Lichens & Ferns of Northwest North America. Lone Pine Publishing, Edmonton, Canada.

By Patrick Lilley

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