Flax-leaf fleabane
Erigeron bonariensis
Family · Asteraceae · Harmless
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The tall, grey, dishevelled weed rising from tarmac cracks in any Peninsular city. It is South American, arrived in the nineteenth century and is today one of the commonest plants on abandoned urban ground.
Town and roadside · Roadsides and waste ground · Fields and pasture · Streams and ditches
Also known ashairy fleabane, asthmaweed
How to tell it
A single upright stem to a metre, covered in rough hairs, with side branches overtopping the tip and giving a dishevelled outline. Narrow, grey-green, hairy leaves. Small closed heads with no visible rays, opening into white tufts of flying seed.
What it is confused with
Canadian fleabane
Erigeron canadensis
The Canadian one is smooth and bright green, with a straight stem and flowers in a broad pyramid at the top; this is grey and hairy, with side branches overtopping the tip. Neither is dangerous, both are exotic.
Open sheet →What it is for
No use to recommend. It matters for another reason: it was among the world's first plants to evolve glyphosate resistance, and is now a serious agricultural problem across the Mediterranean basin.