Hairy fleabane

Erigeron bonariensis

Erigeron bonariensis is a species of Erigeron, found throughout the tropics and subtropics as a pioneer plant; its precise native origin is unknown, but most likely Central America or South America. It has become naturalized in many other regions.Common names include flax-leaf fleabane, wavy-leaf fleabane and Argentine fleabane.
Erigeron bonariensis is a rare alien in south eastern England, found beneath walls and in cracks in pavements and concrete driveways. It flowers in August and continues fruiting until the first frosts (sometimes as late as Christmas Day in Berkshire). It is instantly recognisable by its blue-green foliage, very narrow, undulate leaves, and purple-tipped involucral bracts.