Buttercups are one of the most common showy flowering plant groups but perhaps not as straightforward to identify as it would seem. There are 3 main species of yellow meadow buttercup which we are likely to come across; Creeping Buttercup R repens, Meadow Buttercup R acris and Bulbous Buttercup R bulbosus. They all have yellow 5 petalled flowers and palmately lobed leaves and can be found growing alongside each other. R bulbosus is probably most distinctive when in flower because it has reflexed sepals (turned back to the flowering stem) although the flowering season is short. However R bulbosus prefers neutral to acid soils and as where I live is mainly acid and highly disturbed I have not yet seen one.
One of the key diagnostic features used by Streeter and Stace is that R repens has stolons that creep along the surface of the ground sending out occasional roots. This is the feature that gives the plant its name but it does not mean that every specimen will have rooting stolons although in overall appearance the plant will want to spread and clone to cover a large area.
The other yellow buttercup of the verges is R acris. The flower is very similar to R repens but the lower leaves are more delicate and very deeply divided and the plant has a more upright habit with the flowers sitting above the rest of the plant.
Sometimes the R repens will have mottled pattern on the upper surface of the leaf though this is also a feature of R bulbosus.
However it can be more confusing than it appears, and the plant crib notes that in grazed grassland it can be difficult to differentiate between the three species as all display much variation in leaf shape and size.