It i widespread and common throughout the UK. It is often seen on roadsides and near hedgerows and can also be found in woodland edges.
Cow Parsley (Anthriscus sylvestris)
belongs to the carrot or Apiaceae family (formerly Umbellifera from the French and Latin for sunshade, due to the arrangement of their flowers which is a bit like a flat topped umbrella!). The flowers are small, with five petals, and clustered together to make small umbels (umbrellas) which are then grouped together to make up one large umbel (a compound umbellifer). It can spread quickly in rich damp soil both by seed and its rhizomes (a continuously growing horizontal underground stem.) It often gets mixed up with Hogweed (not to be confused with Giant hogweed) but hogweed flowers in late spring and summer. Also hogweeds leaves are much larger and only coarsely divided while cow parsley has many feathery leaflets. It is probably best not to pick cow parsley unless you are positive of its identity as it can be confused with other umberlliferas such as hemlock (which is poisonous) and giant hogweed (sap burns in sunlight).
For more info see https://www.plantlife.org.uk/uk/discover-wild-plants-nature/plant-fungi-species/cow-parsley