← Species guide
Buddleia (butterfly bush)
Moderate riskBuddleja davidii
The purple butterfly bush that seeds itself into every wall, bridge joint and chimney in Swansea. It is a genuine problem for buildings: roots widen mortar joints and brick cracks, and a mature buddleia can lift coping stones off a bridge parapet.
How to identify it
- Tall woody shrub with arching stems, 2–4m
- Long tapered grey-green leaves, white-felted underneath
- Dense lilac-purple flower spikes like lilac, heavy with pollinators in summer
- Seedlings appearing in gutters, walls and pavement cracks
Why it matters
- Roots exploit and widen cracks in walls, chimneys, bridges and paving
- Blocks gutters and gullies with leaf fall and seed
- Smothers bare industrial ground and slows natural regeneration
How to control it
- Pull seedlings by hand while small — this is the only cheap stage
- Cut mature shrubs to the ground and treat the stump with herbicide immediately
- Remove flowering heads before they set seed where cutting cannot be done
- On buildings, deal with it as part of repointing and gutter clearance, not as a plant problem alone
