Many similarities to : Guernsey Fleabane (Erigeron sumatrensis),
Bilbao's Fleabane (Erigeron floribundus) and to Canadian Fleabane (Erigeron canadensis) which are all in the same genus.
No relation to :
Argentine-pear (Dunalia australis),
Argentine Barley (Hordeum euclaston),
Argentine Pepperwort (Lepidium bonariense),
Argentine Needle-grass (Nassella tenuissima),
Argentine Dock (Rumex frutescens) nor to
Argentine Cockelbur (Xanthium ambrosioides) [plants with similar names belonging to differing families].
Argentine Fleabane is a recent alien introduction (formerly it was accidentally brought into the UK on wool [presumably from Argentina] and became naturalised in Middlesex since 1993, but is now slowly spreading around the UK. It cannot be differentiated from Guernsey Fleabane by either the glands or their stickiness despite what other sources may say. Argentine Fleabane is more sensitive to frosts than either of its two look-e-like-ee's Guernsey Fleabane and
Bilbao's Fleabane. On all three species, Argentine, Bilbao's and Guernsey Fleabanes, the disc florets have 5 lobes whereas Canadian Fleabane usually has 4 lobes (but occasionally 5 lobes). Altogether, all 4 of these Fleabanes mentioned here are a difficult group to differentiate, with the examples found in Britain being a smaller subset of those found in America.