Wall rue
Asplenium ruta-muraria
Family · Aspleniaceae · Harmless
The minute fern growing in mortar joints and limestone cracks, its fronds divided into small fan-shaped paddles that look like rue leaves rather than fern.
Walls and rocks · Uplands
Also known aswall spleenwort
How to tell it
Fronds three to twelve centimetres, in a dense tuft. Divided twice or three times into small fan or wedge-shaped segments, slightly toothed at the edge, leathery and dark green. A mostly green axis, unlike the other black-stemmed spleenworts. It grows only on lime-rich substrate.
What it is confused with
Maidenhair spleenwort
Asplenium trichomanes
Maidenhair spleenwort has a shiny black axis with round leaflets paired like a ladder; this has a green axis and fan-shaped segments divided several times. Both on walls, neither dangerous.
What it is for
No use
It indicates lime mortar and limestone, and a wall covered in it is nearly always an old wall, built before cement.
Where it occurs
Each square is an area with recorded observations of this plant. The lighter background is the set of areas where any of the entries has been observed, and serves as a reference. Note what this is not: it is not where the plant lives, it is where people record it, so trails and towns always look fuller than the mountains. Data from GBIF.
Sources
Community
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