The plant persisted and evolved on sky islands and nunataks in these ranges during glaciation events during the Pleistocene epoch.

[5][4] The shape of the leaves is subterete, nearly circular in cross section, with an outline that can be lanceolate, elliptic-lanceolate, or elliptic-ovate.

[9] The plant reproduces sexually by its tiny, lightweight seeds, or vegetatively when sections of its stem break off and root.

[3] The related narrow-petaled stonecrop (Sedum stenopetalum) can be distinguished by a ridge on the underside of its leaves.

[2] There are significant genetic differences between populations of lanceleaf stonecrop between the Southern Rocky Mountains and the Central Rocky Mountains across the Wyoming Gap and what is now the Wyoming Basin shrub steppe because the lower altitudes serve as a barrier to this and other species with a preference for high elevations.

[12] Additionally, during the most recent glacial period, genetic evidence supports that the species was isolated in sky islands and nunataks that protruded above the glaciers.

[13] The species has two accepted subspecies,[2] though the Flora of North America following the classification by Charles Leo Hitchcock lists them as varieties.

[14] This subspecies was scientifically described as a species and named Sedum nesioticum in 1941 by George Neville Jones.

[22] Lanceleaf stonecrop has a native range across much of western North America from Alaska to New Mexico.

[1] It grows on stony outcrops, dry rocky slopes, and areas of lithosol, places with very thin and poorly developed soils.

[18][25] It is associated with a wide range of stones including limestone, sandstone, marble, andesite, basalt, granodiorite, and granite.

[10] However, the botanist Charles Uhl reports that it is not often found or may be absent from basaltic rocks and lava outcropings.

[26] It is strongly associated with the alpine tundra and subalpine zone along the North American Cordillera, but can be found in many other habitats including on gravelly sites on the Great Plains adjacent to the mountains.

[1] Sedum lanceolatum is almost the sole host plant of the Rocky Mountain apollo butterfly (Parnassius smintheus) in large parts of its range.

[29] Consequently, the larvae often hurry to feed, then switch to another plant within the time window offering the highest nutritional quality.

If the snow melts before March, the eggs hatch while the larval foodplant is still toxic, and the larvae perish.