Canadian horseweed
Tiny flowers, only a few millimeters in diameter.
Erigeron canadensis, Conyza canadensis, horseweed, Canadian horseweed, Canadian fleabane, coltstail, marestail, butterweed, przymiotno kanadyjskie, konyza kanadyjska (Erigeron canadensis L.).

Plant native throughout most of North America and Central America. It is also widely naturalized in Eurasia and Australia. It is a dangerous weed in agriculture. But it contains flavonoids and essential oils that are used to produce perfumes. Anti-haemorrhagic tablets are also made from the herb.