Juniper Haircap Moss

Juniper haircap moss at Painted Rock CA
Scientific Name
Polytrichum juniperinum
Polytrichaceae (starburst and haircap mosses; an acrocarpous moss family)

A colony of juniper haircap moss looks like a tiny forest of juniper sprigs. The leaves are long, rigid, and sharply pointed like evergreen needles, and each ends in a tiny brown tip. The leaves are closely packed and grow out at right angles to the upright stems. The rather transparent margins of the leaves fold over along the sides to cover most of the upper surface of the leaves.

The sporophytes are generally very tall, with very long reddish-brown stalks about 1–3 inches long. The sporophytes arise from the stalk tips of female gametophyte branches in late autumn or early spring and mature in late June. Immature capsules are covered by a densely silky-haired, cream-colored calyptra (the calyptra is a jacket that protects the capsule when it first develops in the tip of the gametophyte, then remains on the capsule for a time like a little hat). Immature capsules are held erect, but when they mature, they tilt sideways. Mature capsules are four-sided at the tops.

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

Similar species: Missouri has approximately 4 more species in genus Polytrichum:

  • P. commune (common in the correct habitats)
  • P. formosum (also called Polytrichastrum formosum)
  • P. ohioense (common in the correct habitats)
  • P. piliferum (rare; a relatively small polytrichum moss)

The taxonomy has been changing in recent years. Seven or eight more Missouri species are in the same family, in the genera Atrichum and Pogonatum.

Other Common Names
Juniper Hairy Cap Moss

Height: Commonly up to 4 inches; sometimes taller, to about 8 inches. One of Missouri’s tallest mosses.

Where To Find

Statewide. This moss occurs globally.

Occurs in moderately dry soil in open, upland woodlands. Very common throughout the Ozarks, in oak-hickory and oak-pine woodlands, often on thin soils over flat rocks and especially over sandstone and granite. Ridges and slopes are favorite places, since leaf litter doesn’t accumulate there and bury the moss.

Various species of haircap mosses, along with Ontario rose moss (Rhodobryum ontariense) and a brothera moss (Brothera leana), are among the characteristic plants of Missouri’s dry sandstone cliff edge natural communities.

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. In this species, the sperm- and egg-producing organs are on separate plants (this species is dioecious). When water — even just a thin layer of rainwater or a few raindrops — 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 tip of the female plant’s gametophyte stem. It obtains nutrients from the gametophyte. When mature, the capsule opens to release spores, which can grow into new gametophyte plants. Carefully jiggle a mature capsule and watch the little cloud of spores waft out.

Mosses also commonly reproduce asexually when a portion of the plant breaks away, gets moved elsewhere, and continues growing as a separate plant.

Mosses have considerable aesthetic and scenic value. Mosses drape around trees and boulders like warm, cozy shawls. They carpet the banks of streams and glisten like emeralds beside seeps and springs. These areas are beautiful in their own right, but mosses make the Missouri landscape even more attractive. This contributes to tourism and to our well-being.

People often cultivate moss as a ground cover. This is especially common in regions where a cool, humid, and cloudy climate makes moss growing easy. Japanese gardeners have raised moss cultivation to an art form. Many people in the Pacific Northwest encourage mosses as a groundcover. But if moss is growing in your lawn, and you don’t want it there, you can reduce the problem by improving the habitat for grass growth and ensuring healthy grass growth in the fall.

Certain species of Polytrichum are used extensively in moss gardens, notably in Japan, where they are probably the most popular mosses for gardening. They are commonly used in the gardens of Japanese Zen temples. The Japanese have cultivated mosses in gardens for thousands of years.

Although most mosses are not eaten by small mammals, mice and rabbits reportedly eat the large capsules of juniper haircap moss. Some insects are known to eat this moss, too, including certain lace bugs, grasshoppers, and the yellow underwing, a noctuid moth that is found worldwide.

A number of birds, ranging from warblers to towhees to robins, have been recorded using the sporocarp stalks of mosses in this genus as nesting material.

Juniper haircap moss and several of its relatives are well-known as some of the earliest plants to recolonize landscapes after forest fires. The term for this is pyrophilous (fire-loving), and pyrophilous plants play an important role as the land recovers from catastrophe.

Like other mosses, haircap mosses lack true veinlike tubes for conducting moisture from the ground into the rest of the plant. Most mosses absorb water directly through the cells of the leaves and stems. Haircap mosses, however, are adapted to survive dry conditions, so their leaf and stem surfaces are coated to prevent water loss — but this also prevents water absorption. Therefore, these mosses must draw water up from the rootlike rhizoids, much like a vascular plant. Specialized cells in the core of the stem permit water to work its way up the plant.

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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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