Shepherd's-purse (Capsella bursa-pastoris)
This is a tough little character! Even in the depths of winter you can find Shepherd's-purse in flower. I have no idea what pollenates it at such a difficult time of year for insects but somehow it must be worth this plant flowering.
Normally a weed of cultivation it thrives in gardens, field edges and areas of disturbed earth but it can also grow where there is minimal soil and can be found in roadside gutters and drains and in other bare, waste places. I have even seen it growing on concrete.
The size of the plant does vary considerably, the harsher the conditions the smaller it is, but in summer and in favoiurable soil it can grow to be quite a strong plant.
It is called Shepherd's-purse because the seeds are heart-shaped and look like little purses and this is one of the easiest ways to identify this species. It is a member of the cabbage family (crucifereae) with tiny flowers but the seed 'purses' are much more visible.
Find out more about the nature of Dorset at my website www.natureofdorset.co.uk