 The custom of dressing the Arbor tree – a black poplar growing in Aston-on-Clun in south Shropshire – with flags on flagpoles every 29 May is almost unique in Britain, although "Bawming the Thorn" at Appleton Thorn in Cheshire is not dissimilar.New flags are attached to wooden flagpoles on the Arbor tree which remain throughout the year.The Arbor tree is a male black poplar tree growing beside a stream at a place where four roads meet.