Buddleia‘s are certainly a beautiful shrub but are one of the most destructive plants around, they are banned in some places and are regarded as a noxious weed as they will crack, move and lift foundations of masonry they should be grown in a clear area not near any construction and their seed spread and grow in almost any place they land, however they do attract butterflies which is nice to see. Our local council have planted a dwarf variety in our town they look exactly like the normal size ones but in miniature which apparently are building friendly.
David.