Dandelion, Taraxacum spp.
Such a tough plant, one of the most successful coloniser of disturbed soils, a true pioneer when it comes to repair damaged areas and start the process of organic matter accumulation. Its roots dig down in the soil and bring up nutrients. Its cycle's fast, allowing for mobility and range thanks to the wind-dispersed seeds. Naturalised in all 6 continents, even in the sub-Antarctic regions. A remarkable co-evolutionary species. I read once a study suggesting that a bright yellow flower 'brings about positive emotional feelings' in those who encounter it.
That works for me :)
Check Wild Food Map for its location>>>