Oil Spill Moss

Oil spill moss growing on a large fallen log
Scientific Name
Platygyrium repens
Hypnaceae (plait mosses; a pleurocarpous moss family)

Oil spill moss creates thin mats atop fallen logs and on tree trunks. Its leaves and stalked capsules are tiny. A patch of this common, branching species looks something like a piece of olive-green velvet, with patches of darker, bronze-colored areas that look like grease stains. The edges are lighter green and gold.

The leaves are tiny (only about 1 mm long), with narrow, pointed tips; under a microscope, you can see 2 short ribs at the leaf base. The leaves are usually pressed against the stem, especially when it is dry. The branch tips usually curve upward. Under close examination (use a hand lens), you usually will see a cluster of tiny branch sprouts (brood branchlets) at the tips of the branches — these, and the fallen-log habitat, are key identifying features.

The sporophytes have stalks (setae) about ½–¾ inch long; the capsules are about ⅛ inch long, narrow, nearly cylindrical, with a pointed lid (operculum). Capsules are present from late summer through spring.

Learn more about Missouri’s mosses on their group page.

Similar species: There are hundreds of moss species in Missouri, and many of them are pleurocarpous (mat-forming, or carpet mosses). Without a hand lens, you may have a difficult time distinguishing among the many branching species that commonly grow on logs and trees. Missouri has about 20 species of mosses in family Hypnaceae, the family that contains oil spill moss.

Other Common Names
Flat Brocade Moss

Width: forms mats several inches wide. Can cover the top surface of entire logs.

Where To Find

Statewide. Widespread in eastern North America.

The substrate is a key identifier for this common moss species: it is almost always found on logs, stumps, and other weathered and decaying wood, and on tree trunks and tree bases. This moss often occurs on barkless wood. It is usually found in shady, moist woodlands and forests. Occasionally, it occurs on rocks or on soil, in shady places.

Native Missouri moss.

Life Cycle

As with other mosses, this species has alternating generations. The plant we usually think of as the moss is the gametophyte generation (it’s a gamete-, or sex-cell-bearing plant). In separate organs, it produces sperm and eggs. When water, even a thin layer of rainwater, is present, the sperm can swim to the eggs and fertilization occurs.

The resulting offspring plant, called a sporophyte (spore-bearing plant), grows out of the female organs of the gametophyte. In this species, the sporophyte takes the form of a stalked capsule growing out of the sides and tips of the branching gametophyte stems. It obtains nutrients from the gametophyte. When mature, the capsule opens to release spores, which can grow into new gametophyte plants.

Mosses also commonly reproduce asexually when a portion of the plant breaks away, gets moved elsewhere, and continues growing as a separate plant. Oil spill moss has unusual growths called “brood branchlets” or “brood bodies”: these are the numerous tiny sprouts that arise at the stem tips. These can readily fall off and grow into new plants.

Who knew that you could describe a moss as if it were a piece of olive-green velvet with grease stains on it? The alternate common name, flat brocade moss, also references the shiny-looking, light-dark appearance of this moss.

The curious family name, Hypnaceae (hip-NAY-cee-ee), comes from the genus name of several other members of the family (Hypnum). Hypnos was the Greek god of sleep, and presumably some of these mosses were associated with sleep because dried mosses were commonly used as pillow stuffing.

Mosses can create a microhabitat where many types of insects and other invertebrates live. Centipedes, sowbugs, springtails, snails, and a wide variety of other small animals live in and around mosses. Some of the animals that take shelter in mosses on fallen tree logs may contribute to the logs’ decomposition. Shrews, salamanders, frogs, tiny snakes, and other insectivores hunt for a variety of small animals among the mosses.

Many kinds of birds, as well as mice and other mammals, use mosses in nest building. Mosses cushion fragile eggs and delicate, naked young; insulate against cold weather; and camouflage the nest, concealing it from predators. Even bumblebees gather mosses for their nests.

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Similar Species
About Mosses, Liverworts, and Lichens in Missouri

Mosses, liverworts, hornworts, and lichens seem rather similar, but these organisms are in very different groups. Mosses, liverworts, and hornworts are small, low plants usually found in damp habitats. Unlike more familiar plants, they lack veinlike structures and do not produce flowers or seeds — instead, they produce spores. Meanwhile, lichens are not plants at all: they are a collection of different fungi that have photosynthetic algae living within their tissues.

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