This abundant, diverse moss genus is the foundation of many wetland ecosystems in Alaska. These plants are natural sponges, holding up to 30 times their weight in water. They grow in cushions, hummocks, lawns or aquatically, often forming incredibly deep mats, insulating the soil from heat and protecting permafrost. And, of course, once the ground is frozen, water can't drain away, amplifying the bog effect. Sphagnum also acidifies the environment, allowing for only a handful of bog-adapted species to co-habitate with it. There are 24 species of Sphagnum in Denali. Peat moss species come in beautiful colors—bright muppet green, shades of pink and red, and dark purple. The morphology of Sphagnum mosses is unique. Its branches are produced in clusters, some hanging down along the stem and some ascending. At the top of the stem, branches are compressed into a tufted head. The leaves have two types of cells: those that photosynthesize, and dead cells that serve only to absorb water. Spore releasing capsules (only rarely produced), are dark, round and stalked less than a centimeter above stems. Capsules open by a 'pop-gun' pressure-driven mechanism, spraying spores into the wind. Distinguishing among species relies on branching patterns, growth form, color and leaf cell characteristics.

Peat mosses typically reproduce asexually through lateral branching and fragmentation. Most species are dioecious, but some do produce male and female sexual organs on the same plant.

Sphagnum is the major contributor to the formation of peat, widely used in horticulture today, and formerly used as fuel and house-building material. Native Alaskans traditionally used Sphagnum as a diaper lining (due to its absorbtive capacities). It was also mixed with seal oil and left to go rancid, then used as caulk for kayaks.

Abundant in the Northern Hemisphere, but also found in restricted parts of Oceania and South America.