I am sure many of us see buttercups and think "that's a buttercup"! Well, it gets more difficult if you ask "but which species of buttercup?" There are several, eight in fact, that look like traditional buttercups! It's not quite that bad as some are very rare now having been affected by intensive spraying of our fields.
The corn buttercup, once common, is now all but extinct. Other species are quite distinctive in their own way so it really leaves meadow, creeping and bulbous as the most likely choice if it's a standard buttercup you are looking at. The first thing to do is to gently bend the flower head over and look at the sepals, if they point downwards, as in this photograph, then it is a bulbous buttercup (Ranunculus bulbosus).
The bulbous buttercup is very common on dry grassland, especially on chalk, and so is very common in Dorset.
So, now you know how to tell if it is a bulbous buttercup all you have to do is sort out the difference between meadow buttercup and creeping buttercup!