Current populations descended from Atlantic coastal refugia after the last ice age, with genetic evidence supporting classification as a single species despite morphological variation.

Sphagnum fimbriatum is assessed as a least-concern species across Europe due to its widespread distribution and stable populations, though it faces regional threats.

[7] Molecular studies have confirmed this complex taxonomic position, with genetic evidence supporting both its distinctness from most Acutifolia members and its unusual relationship with section Squarrosa.

[9] The plant displays small, distinctive head-like structures (capitula) with noticeable protruding stem buds, and its colour varies from bright green to pale yellowish-green.

[10] Plants collected from South America, particularly Argentina, tend to be more robust with larger stem leaves than those from similar climatic conditions in the Northern Hemisphere, though they remain morphologically and genetically part of the same species.

[8] The leaves' cellular structure shows regular patterns of strengthening fibers and has many small holes (pores) where cells meet (commissures).

[8] Chemical analysis has identified 13 distinct phytochemicals in S. fimbriatum, including caryophyllene, phytol, methyl esters of hexadecanoic and heptadecanoic acids, and various phenol derivatives.

These species can be distinguished by their habitat preferences and morphological differences: S. teres typically grows in more nutrient-rich environments and has a dark brown stem, whilst S. squarrosum is generally more robust and features distinctively spreading branch leaves.

[7] Sphagnum fimbriatum typically grows in moderately nutrient-rich (mesotrophic) wetland environments, where it forms soft, raised mounds (hummocks) or loose carpets in partially shaded conditions.

[12] The species shows a particular preference for damp woodland habitats, especially those dominated by willow (Salix) or birch (Betula) trees, often growing alongside purple moor-grass (Molinia).

[7] The species is particularly effective at colonising bare soil surfaces, including disturbed habitats, and shows a distinct preference for establishing itself in sites with low phosphate content.

[7] In North America, its range extends from the Arctic southward to West Virginia, Ohio, Indiana, Illinois, Iowa, and South Dakota, with western populations in Colorado, Idaho, and California.

[12] In the British Isles, the species is widespread and generally common, though it occurs less frequently in central southern England, north-western Scotland, and western Ireland.

[10] A single genetic type dominates continental Europe, suggesting the species passed through a population bottleneck during glaciation before expanding rapidly.

Certain genes, such as GapC (encoding glyceraldehyde 3-phosphate dehydrogenase), show evidence of molecular adaptation, suggesting selective pressures contribute to the species' success in different environments.

This genetic connectivity helps explain how the species has maintained coherence across its extensive global distribution, despite showing local adaptation to different environmental conditions.

This reproductive strategy, combined with effective spore dispersal, helps explain the species' success in colonising new territories despite potential genetic bottlenecks.

It grows in moderately calcareous waters and tolerates pollutants, including heavy metals and salt levels up to 300 milligrammes per litre of chloride.

[15] Success in its pioneer role appears linked to specific genetic adaptations that improve its colonisation ability, competitive capacity, and vegetative growth, particularly in northern regions.

[12] However, despite being an effective coloniser, S. fimbriatum is not a strong competitor once established and can be displaced by other species better adapted to stable conditions in later succession stages.

A study found that nitrogen fixation in S. fimbriatum is largely unaffected by the specific composition of its diazotrophic bacterial community, which is predominantly composed of bacteria from the Rhizobiales order within Alphaproteobacteria.

After fertilisation, the developing plant embryo first grows within the protective base of the female structure (called the archegonial venter) before moving into the tip of the branch.

They first develop into a flat, single-layer-thick structure (called a protonema) that produces tiny root-like filaments (rhizoids) to attach to the growing surface.

[21] Molecular evidence suggests that S. fimbriatum predominantly reproduces through self-fertilisation, a strategy that may have aided its rapid post-glacial spread by allowing single spores to establish new populations.

This vegetative reproduction ability persists even under moderately saline conditions, with the species capable of producing new growth in environments with chloride concentrations up to 500 mg/L.

While spore dispersal enables long-distance colonisation, vegetative reproduction becomes the dominant means of local population expansion once the species is established in a new location.

Conservation strategies proposed for Turkish Sphagnum species emphasise protecting rare peatlands to mitigate ongoing habitat degradation.

[23] Sphagnum fimbriatum faces the same threats as other European wetland species: habitat drainage for agriculture, nutrient pollution from farming, dam construction, and peat extraction.

[24] The species shows distinct chemical properties from other Sphagnum mosses when used as a growing medium, containing notably higher levels of soluble potassium.

However, these chemical differences can lead to chlorosis (yellowing of leaves) in some plants grown in pure S. fimbriatum substrate, suggesting its optimal use may be as part of a mixed growing medium rather than alone.