Common as muck.

My favourite colour of flowers is blue; forget-me-nots, delphiniums, lobelia, bluebells...you pick any blue flower, I'll love it! Agapanthus and cornflowers are prodigiously blooming around Vinoland right now and they look so pretty. So, it goes without saying that one of my favourite weeds is common chicory (Cichorium intybus) because it too has a blue bloom.
Chicory has a deep taproot which can penetrate the hardest of soil types and can be useful as a vineyard cover crop. This beneficial weed can be planted to aid in the management of deficit vineyard irrigation programmes because it can apparently improve wine quality in overly vigorous vineyards (think reduced malic acid and methoxypyrazine levels in Cabernet sauvignon.) It is also very drought resistant, which is probably the reason it grows so successfully, and abundantly, along roadsides this time of year. However, it is a tall weed so don't expect to easily navigate any vineyard that is planted to chicory.
The taproot of chicory is also cultivated as a coffee substitute. Does anyone remember Camp Coffee? Growing up, there was always a bottle that lurked in the back of a cabinet in my mother's kitchen. It may still be there!