Some plants flower only on new wood so the tip growth is the most recent. Another reason is that a cold winter can destroy the most recent output of new growth on a shrub so that only the tip growth from the current summer plant can bloom. In early spring you can cut back your butterfly bush or buddleja and let it start all over and perhaps you will like the blooming location of the flowers more after this drastic haircut. Most butterfly bush shrubs look best when they are cut to the ground in early spring every year. You can also prune off the faded blooms in the summer to keep the plant looking tidy. Keep growing, Marianne Binetti