Lycopodium clavatum (common clubmoss, stag´s-horn clubmoss, running clubmoss, or ground pine) is the most widespread species in the genus Lycopodium in the clubmoss family.

 Lycopodium clavatum is a spore-bearing vascular plant, growing mainly prostrate along the ground with stems up to 1 m long; the stems are much branched, and densely clothed with small, spirally arranged microphyll leaves. The leaves are 3–5 mm long and 0.7–1 mm broad, tapered to a fine hair-like white point. The branches bearing strobili or spore cones turn erect, reaching above ground, and their leaves are modified as sporophylls which enclose the spore capsules or sporangia. The spore cones are yellow-green, long, and 5 mm broad. The horizontal stems produce dichotomous roots at frequent intervals along their length, allowing the stem to grow indefinitely along the ground. The stems superficially resemble small seedlings of coniferous trees, though it is not related to these at all.

Distribution: Lycopodium clavatum has a widespread distribution across several continents. There are distinct subspecies and varieties in different parts of its range:

• Lycopodium clavatum subsp. clavatum
• Lycopodium clavatum subsp. clavatum var. clavatum (Europe, Asia, North America)
• Lycopodium clavatum subsp. clavatum var. aristatum (Mexico, Caribbean, Central America, northern South America south to northern Argentina)
• Lycopodium clavatum subsp. clavatum var. asiaticum (Japan, northeast China)
• Lycopodium clavatum subsp. clavatum var. borbonicum (central and southern Africa)
• Lycopodium clavatum subsp. clavatum var. kiboanum (mountains of tropical Africa)
• Lycopodium clavatum subsp. contiguum (southern Central America, northern South America; syn. Lycopodium contiguum)

Although globally widespread, like many clubmosses, it is confined to undisturbed sites, disappearing from farmed areas and sites with regular burning. As a result, it is endangered in many areas. In the UK it is one of 101 species named as a high priority for conservation by the wild plant charity Plantlife.
Other common names
Common names for this species include wolf´s-foot clubmoss, common clubmoss, wolf-paw clubmoss, running ground-pine, running pine, running moss, princess pine, and others.
Use
The dried spores of this moss are explosive if present at high density in air. They were used as flash powder in early photography and are still used in magic acts. See lycopodium powder.

The plant has been used in Finnish traditional medicine as a diuretic and as a remedy for rickets.
Active constituents
Bioactive secondary metabolites in clubmosses include triterpenoids with acetylcholinesterase inhibitor activity isolated from this species.