- Family: Buttercup Family – Ranunculaceae
- Growing form: Perennial herb. Often forms mat-like stands.
- Height: 2–6 cm (0.8–2.5 in.) high. Stem up to 40 cm (16 in.) long, limp, thin, with runners, often rooting from all nodes, internodes clearly arching.
- Flower: Corolla regular (actinomorphic), yellow, shiny, usually 5–10 mm (0.2–0.4 in.) wide; petals 5, longer than sepals. Sepals 5, glabrous–hairy, dropping. Receptacle glabrous–hairy. Stamens many. Gynoecium separate, with many pistils. Flowers solitary, terminating stem, flower-stalk grooved.
- Leaves: Alternate, often as a rosette around rooting nodes, almost all stalked. Blade lanceolate–linear, blunt, with entire margins. Blades possibly lacking on submerged leaves.
- Fruit: Quite elliptic, glabrous, 1.3–1.9 mm (0.52–0.76 in.) long achene, bristle 0.3–0.4 mm (0.012–0.016 in.) long, curved. Achenes in clusters.
- Habitat: Open, gravelly and sandy shores on lakes, rivers and brackish springs, on the water line or submerged, gravel pits, streams, ditches.
- Flowering time: (June–)July–August.
Creeping spearwort demands quite an open habitat, which is easy to understand from the plant’s appearance: crawling on the ground with delicate leaves, it wouldn’t survive in amongst larger plants. It thrives on barren lake shores by clear water in sandy and stony, clay-rich ground. The plant declines if the water becomes more nutritious, and it is rarely found around such lakes.
Above the water line creeping spearwort often flowers abundantly. It also commonly grows completely submerged in lake water, but in these cases it remains flowerless – sometimes however it can become inspired to open its flowers deep below the surface. Creeping spearwort does best in under 40 cm (16 in.) of water and it has a limit of approximately 70 cm (28 in.). Submerged plants can propagate themselves vegetatively by spreading small shoots on the waves.
Creeping spearwort is sometimes mistaken for lesser spearwort (R. flammula), and it can be difficult to tell their delicate forms apart. Creeping spearwort usually has smaller flowers and the bristle on its achene is longer. The species also cross-breed, and the hybrids do not necessarily differ from the parent plants apart from the fact that some of their pollen grains are withered. In Finland however the species do not usually cross-breed: they favour such different habitats that they rarely meet.