Lesser burdock (Arctium minus) is complicated! There are actually three subspecies of lesser burdock and the differences are minimal unless yolu are something of an expert botanist with an eye for detail. My field guide, "Wild Flowers of Britain and Ireland" by Marjorie Blamey, Richard Fitter and Alastair Fitter describes these differences. The subspecies Arctium minus ssp minus has flower stalks of less than 1cm with the florets sticky or downy. The ssp nemorosum has flower stalks of less than 1cm with the florets never sticky or downy! This subspecies is sometimes called the wood burdock. The third ssp pubens (sometimes called the intermediate burdock) has flower stalks between 1cm and 4cms.
The first of these is the most common and I am afraid I cannot even begin to try and sort out which of the many burdock plants I see belongs to which subspecies so I record them all as lesser burdock!
It gets its name for from the seed heads that have hooks, just like velcro, and attach themselves to passing animals and human clothing, These are called burrs hence the name burdock.