Generally butterfly bushes are tolerant of any soils, particularly in full sun. Evergreen or deciduous shrubs, with opposite leaves (except for the contrary B. alternifolia). 4-petalled flowers, in small rounded heads, or long spikes, often sweetly scented. Many will flower in late summer, coinciding with the arrival of migratory butterflies. Most (but check the species) can be left unpruned over winter, but then cut back to a framework of your choice during spring.
Buddlejas do not get their English name of Butterfly-bush for nothing: one particular bush of B. davidii in our garden on one morning on July 2023 had more than 200 butterflies of at least 8 species visiting its nectar resources! Add to that a myriad of bees, moths, wasps, hoverflies and other insects and its value cannot be overstated. However, it does have a propensity to escape its garden confines, and flourish on brownfield sites especially, often excluding other valuable plants. But that cat is well out of the bag, so it is unlikely that containment steps to avoid its repeated escape from gardens would have any effect. Fortunately, other choice cultivated species seem, with the possible exception of B. globosa, less likely to establish in the wild.