Pershore roofs, specifically
Low in the Avon valley, under the fruit trees: what turns Pershore roofs green.
Pershore is on the flat floor of the Avon valley, where the river curves past the town on its way down to Tewkesbury and the Severn. The Old Bridge, the abbey and the long Georgian street make it one of the best-looking towns in Worcestershire, but the low, damp setting is hard on roofs. The Bridge Street and Wick side of town floods often enough to have its own Environment Agency flood-warning area, and the air on the valley floor stays moist even in summer. That moisture feeds moss, lichen and gloeocapsa algae, so Pershore roofs usually grow more than the same houses would on higher ground towards Bredon Hill.
The town centre has its own reasons. In 1964 the Council for British Archaeology named Pershore one of only 51 Gem Towns, largely for the long curve of Bridge Street, Broad Street and the High Street. Those tall Georgian houses stand side by side, throw each other and the yards behind into shade for much of the day, and many still have Welsh slate or hand-made clay that stays wet far longer than modern tile. A roof that looks black from the street is normally a deep layer of moss in the slate laps, often with rust marks running from old lead and valley metal.
Then there's the fruit. Pershore is plum country: the Pershore Yellow Egg, Purple Pershore and Pershore Emblem plums all came from here, and the town still holds a plum festival each August. Plenty of gardens have fruit trees close to the house. Fallen leaves and the constant drip keep the roofs under them damp, so the north-facing, tree-shaded pitch is usually the first in Pershore to go green.
Away from the centre, the housing on Allesborough Hill and around Three Springs Road is mostly post-war and modern concrete interlocking tile. Spores catch on its rough face and the valley damp lets them spread, so we take the bulk of the moss off by hand from a tower or roof ladder and then apply biocide.
We don't pressure-blast roofs in Pershore. On ageing concrete tile the protective surface is already thin, and on the conservation area's Welsh slate and clay, high pressure cracks and strips the surface. Either way you'd get one clean season and a shorter-lived roof. Lifting the moss by hand and treating with biocide is gentler and lasts much longer.