Butterfly bushes (Buddleia davidii) are lowing-growing perennial shrubs that have clusters of red, pink, purple or white flowers, which typically bloom from spring until fall. Deadheading--or pinching off--spent blooms encourages more blooms. Fertilizing your bushes once a year in the spring also encourages more blooms, as well as more lush green growth. Butterfly bushes are not heavy feeders, however, and may not need fertilizing in order to bloom and grow well.
Determine if your butterfly bush needs fertilizer. If the soil was amended with organic matter (e.g., compost) prior to planting, and you add mulch to the planting bed each year, your bush probably does not need fertilizer. Organic matter and decomposing mulch creates fertile soil in which fertilizer is not needed.
Sprinkle a balanced granular fertilizer, such as one labeled 10-10-10, evenly around the soil of each bush. The fertilizer should not make contact with the stems or crown of the plant. Follow the dosing instructions on the label since each type of fertilizer has different strengths.
Water the plants well with about 2 to 3 inches of water. You must always water your plants whenever you apply a granular fertilizer.
Add a 2-inch layer of mulch, such as leaves or pine needles, around the base of each bush. The mulch will decompose over time and will help create a fertile soil bed in which you do not need to add fertilizer the next year.