"This species is a vital indicator of mountain health but is currently under threat. In some regions like Maine, it is documented in only a few counties due to its scarce habitat. It is also highly vulnerable to airborne nitrogen pollution from vehicle exhausts, which is devastating populations on mountain summits. Protecting its remaining habitats from heavy hiking use and pollution is critical for its survival."
Since Alpine clubmoss ( Diphasiastrum alpinum ) is a rare wild plant rather than a commercial product, here are reviews from the perspective of a nature enthusiast, a gardener, and a conservationist. Nature Enthusiast’s Perspective alpine clubmoss
Glacial. It is an extremely slow grower; it can take up to 20 years for a new plant to fully mature from spores. "This species is a vital indicator of mountain
Diphasiastrum sitchense (Rupr.) Holub - Rare Plants - Maine.gov Protecting its remaining habitats from heavy hiking use