When we bought our butterfly bush from Redmill Nursery in Durham last year,
the guy there told us that these bushes should be pruned on a 5-year cycle
in the Fall. The first year, prune them back to the first division of the
branches; the second year, to the second division, and so on up to four
years. In the fifth year, prune them back down to the first node again. I
don't know what happens if you don't do this, but he was pretty insistent
that it be done this way.

Ours got yellow and had holes in the leaves earlier (two weeks ago) and we
sprayed it with insecticide (something general). It seems to have recovered
enough to put out new growth and is now near to blooming.

-Jenny