Care of Butterfly Bush (Buddleja)

Question from Judy:
My Buddleia is 10 years old and for the past couple of years, it just looks scraggly/leggy, droopy, yellowing leaves, few and puny blossoms. What am I doing wrong??? For the first few years, it produced beautifully. We have a large tree in the yard that has probably cut off some of its sun as it has grown, but the Buddleia still gets quite a bit of sunshine — morning till noon or later.

Answer from Pat:
Your buddleja probably needs some harsh pruning now in late summer after bloom to renew the plant. Cut down some of the old stems so it can send up new ones. Fertilize after pruning so it can regrow with fresh stems to bloom next year. It sounds starved for fertilizer or maybe drainage is not good. Yellow leaves can mean lack of nitrogen, but they could also mean poor drainage. See below for a run-down on total care.

Butterfly bush (Buddleja) is reputed to be drought-resistant but in sandy soil this plant needs a lot of water and in any soil it needs regular irrigation in my opinion. It needs good drainage, but hates bone-dry soil. Additionally, Buddleja’s need a balanced fertilizer for growth and bloom. Fertilize at intervals throughout the growing season and make sure there’s plenty of phosphorus and potassium in the product you use. Deadhead faded flowers or they will stop blooming. After bloom cut the stems that have bloomed back by two or three feet. Otherwise the plant will get very leggy. Each year, in fall remove some of the oldest stems all the way to the ground to renew the plant and get it to send up fresh new growth. These plants really need a fertile soil and if fed and watered will please you with a good display of blossoms. In too much shade, however, you will not get many flowers and 3 or 4 hours on the east side of your home might be a bit sparse. Instinctively, I think the other factors are causing your problem, not the lack of sun. When stems are old and crowded flowers will get smaller and smaller on these worn out stems. You need to get the plant to put out new growth but don’t cut it all down at once. Try removing 1/3 now, 1/3 in early spring, and 1/3 next fall.