Flat-Branched Tree-Clubmoss (Lycopodium obscurum)

Lycopodium obscurum, the Flat-Branched Tree-Clubmoss, is the little evergreen “tree” of eastern woodlands. Its upright shoots, usually 4 to 10 inches tall, branch like a tiny spruce or hemlock, and colonies of them stand in rows across the forest floor, joined by stems that run underground. Generations of New Englanders have called it princess pine or ground pine. Many current floras place it in the genus Dendrolycopodium, as Dendrolycopodium obscurum, and USDA PLANTS lists it under the odd common name “rare clubmoss”, although it is one of the commonest clubmosses in the Northeast.

A clubmoss is not a moss. Clubmosses are lycophytes, an ancient group of vascular plants with true roots, stems and leaves, related to the tree-sized lycophytes of the Carboniferous coal forests. Like ferns they reproduce by spores, not seeds. In late summer this species produces narrow yellow-green spore cones directly at the tips of its upper branches, and they shed fine yellow spores in fall.

Tree-clubmosses were once cut by the truckload for Christmas wreaths and garlands, and colonies recover very slowly. They cannot be grown from nursery stock in any practical way: the plant depends on soil fungi for part of its life, and dug pieces almost never survive transplanting. This page is an identification and appreciation guide, with notes on where it grows and how to look after colonies on your land. Like other clubmosses it contains toxic alkaloids, so it should never be eaten.

Identification

Three very similar tree-clubmosses grow in eastern North America: flat-branched tree-clubmoss, prickly tree-clubmoss (Dendrolycopodium dendroideum) and Hickey’s tree-clubmoss (Dendrolycopodium hickeyi). Older books lumped all three under Lycopodium obscurum, so records and field guides do not always separate them. A hand lens and a look at the main stem and side branches usually settle it.

Growth Form

The plant has a horizontal stem that creeps several inches below the surface, out of sight in the leaf litter and soil. Upright shoots rise from it at intervals, each with a single main stem that branches several times into a bushy, tree-shaped crown. A colony looks like a grove of evergreen seedlings, but every shoot is part of the same underground network.

Leaves & Branches

The leaves are small, narrow and needle-like, about 1/8 inch long. On the main stem below the branches they lie flat against the stem, so the lower stem looks smooth. In prickly tree-clubmoss those leaves spread outward and feel bristly. The side branches of flat-branched tree-clubmoss are flattened in cross-section, because the leaves on their lower side are smaller and twisted, while Hickey’s tree-clubmoss has round branches with leaves of equal size all around. The plant stays deep green all winter.

Spore Cones

In summer, slender yellow-green spore cones (strobili) form at the tips of the uppermost branches, one to several per shoot. Each cone is about 1/2 to 1 1/2 inches long and has no separate stalk, which separates the tree-clubmosses from the fan clubmoss and running-pines, whose cones are held up on long stalks. The cones ripen and release clouds of yellow spores in late summer and fall, and the empty, papery cones can stay on the plant into winter.

Life Cycle

Like all clubmosses it has a two-stage life cycle. A spore that lands in suitable soil can grow into a tiny underground gametophyte with no chlorophyll, which lives on sugars supplied by soil fungi and may take many years to mature. A new green plant grows from the gametophyte after fertilization. This process is so slow and uncertain that most colonies spread by their underground stems instead.

Native Range

Flat-branched tree-clubmoss is native to eastern North America. USDA PLANTS records it from 25 states and the District of Columbia, from Maine and Minnesota south through the Appalachians to Georgia, Alabama and South Carolina. In Canada it grows in Ontario, Quebec, New Brunswick and Nova Scotia.

It is most common in New England, New York, Pennsylvania, the northern Great Lakes states and the Appalachian Mountains. Toward the south it is largely confined to the mountains and upper Piedmont, and at the western edge of its range, in Illinois and Minnesota, it is much less frequent. Because the three tree-clubmosses were long treated as one species, older range records may include its two close relatives.

It grows in moist to fairly dry, acid forests: northern hardwood and mixed hardwood-conifer woods, oak and pine forests, hemlock ravines, the edges of bogs and swamps, and young forests on old farmland. Colonies are often found where the soil has a thick layer of leaf litter and has not been plowed for many decades.

📋 Regional plant lists featuring Flat-Branched Tree-Clubmoss: New York, Pennsylvania & Northern New Jersey · Ohio & Indiana · Michigan, Wisconsin & Eastern Minnesota · Kentucky & Tennessee · Connecticut, Massachusetts & Rhode Island · New Hampshire, Maine & Vermont · Maryland, Virginia & West Virginia · Delaware, Southern New Jersey & Long Island · Illinois, Iowa & Missouri · Alabama, Georgia & Mississippi · North & South Carolina

Growing & Care Guide

Flat-branched tree-clubmoss is a plant to admire and protect rather than plant. It is very hard to transplant or propagate, and nursery-propagated stock is rarely, if ever, available. Never dig it from the wild or cut it for decorations. The sections below describe the conditions it grows in and how to care for colonies that already exist on your property.

Light

In the wild it grows in light to fairly deep shade under hardwoods, pines and hemlocks, and in partly open young forests. It does not tolerate open, sunny ground for long.

Soil & Water

It needs acid, well-drained soil with a layer of decaying leaves, usually sandy or loamy and low in nutrients, that stays moist for most of the season. Lime, fertilizer, compacted soil and the rich, disturbed soil of garden beds all work against it.

Planting Tips

This is not a plant to add to a garden. Dug clumps carry only a short piece of the underground stem and almost always die within a year or two, and the plant depends on fungi in the forest soil. If a colony already grows on your land, protect it: keep foot traffic, digging and machinery away, leave the leaf litter in place, and do not mulch, fertilize or lime the area. For a planted evergreen ground cover in shade, partridgeberry and checkerberry are both native and available from nurseries.

Pruning & Maintenance

No maintenance is needed. Do not cut the shoots for wreaths or table decorations. Removing invasive plants, such as Japanese barberry or Japanese stiltgrass, that crowd into a colony is the most useful thing a landowner can do.

Propagation

Flat-branched tree-clubmoss spreads naturally by its underground stems and, rarely, by spores. Spores grow into underground gametophytes that need soil fungi and can take many years to produce a new plant, so propagation from spores is not practical, and transplanted sections seldom establish. Leave all wild plants in place.

Landscape Uses

• Nature study: an easy-to-find example of the ancient lycophyte lineage, especially obvious in winter woods
• Woodland stewardship: colonies mark long-undisturbed forest soils and are worth protecting during logging or construction
• Photography: miniature “forests” of evergreen shoots, striking in snow and fall leaves
• Teaching: illustrates spore reproduction, plant evolution and plant-fungus partnerships

Wildlife & Ecological Value

Flat-branched tree-clubmoss is not an important food plant, but its evergreen shoots add year-round cover and structure to the forest floor.

For Pollinators

Clubmosses do not flower and produce no nectar, so this plant has no value for pollinators. Its spores are spread by wind.

For Birds

Colonies provide some cover for ground-nesting and ground-feeding birds and for the insects and spiders they eat. Birds do not generally feed on the plant itself.

For Mammals

Deer and other mammals rarely browse it, probably because of its tough texture and alkaloid content. Small mammals, salamanders and other small animals shelter among the shoots.

Ecosystem Role

Its underground gametophyte stage depends on mycorrhizal fungi, tying it to the fungal networks of the forest soil. The evergreen shoots keep photosynthesizing in spring and fall when the canopy above is bare, and the long-lived colonies help hold leaf litter and soil in place.

Cultural & Historical Uses

For generations tree-clubmosses were gathered in large quantities in the Northeast as “princess pine” and “ground pine” for Christmas wreaths, swags and garlands. Because a colony may take decades to grow, heavy harvesting depleted them in many places, and several states regulate commercial collection. Choosing wreaths made from cultivated greenery helps protect wild colonies.

Clubmoss spores, sold as lycopodium powder, are very fine, water-repellent and flammable. They were once used in flash powder, stage effects and fireworks and by pharmacists to coat pills. Most commercial powder came from other species, mainly running clubmoss (Lycopodium clavatum).

The name Lycopodium means “wolf’s foot”, from the resemblance of the branch tips of some species to a paw. Dendrolycopodium adds the Greek word for tree, and obscurum means “dark” or “hidden”. Safety note: clubmosses contain lycopodium alkaloids that can be toxic, so never eat any part of the plant or use it in home remedies, and keep children and pets from chewing it.

Frequently Asked Questions

Is princess pine a moss or a pine?
Neither. It is a lycophyte, a vascular plant with roots, stems and leaves that reproduces by spores. It is more closely related to ferns than to true mosses, and it is not related to pines at all.

Can I plant flat-branched tree-clubmoss in my garden?
In practice, no. It is very hard to transplant or propagate, it depends on soil fungi, and nursery stock is rarely available. Wild plants should never be dug. If you already have a colony, protect it.

How do I tell it from prickly tree-clubmoss?
Look at the main stem below the branches. In flat-branched tree-clubmoss the leaves there lie flat against the stem and the side branches are flattened. In prickly tree-clubmoss the main-stem leaves spread out and feel prickly, and the branches are round.

Is flat-branched tree-clubmoss poisonous?
Clubmosses contain alkaloids that can be toxic if eaten. Do not eat it or use it in home remedies, and keep pets and children from chewing it. Handling the plant is not considered dangerous.

Can I collect it for Christmas wreaths?
Please don’t. Colonies take many years to grow and recover very slowly from cutting, and some states regulate collection. Use cultivated greenery such as fir, pine or cedar boughs instead.