I guess it could be a reversion but the reversions I've seen ( although not many I admit) have involved more than one branch ...it could be some sort of mutatation ...in which case the leafs would likely be a differnt shape and possibly differnt color ...if it is differnt enough it may be worth keeping propagating but only if it is especially nice although the Japanese consider them to be VERY special/ precoius. If it is not special even if it is a mutation and not reversion and it really bothers you I'd wait til late fall early winter and cut it off totally with a clean achohol sterilized saw or clippers depending on how big it is Oh by the way it's 'Ukigumo'...David

The mutation has no special attributes. I will prune it off. Thanks David