We have five butterfly bushes in our back yard that have purple blooms. At...
We have five butterfly bushes in our back yard that have purple blooms. At least that's the way it was until about four years ago, when one of the bushes started putting out white blooms, but not all over. We've had the bushes in a rear corner of the yard since 1996 and we've always cut them down to about 8 inches around the end of March. Why would a butterfly bush that's had all purple blooms for fifteen years start putting out white blooms on most, but not all of the bush? Could it be that something got into the soil that it's planted in?
We can't say for certain what is occurring. Doubtful that the soil is the cause of the color change. A couple of ideas:
Plants do produce mutations or "freak" branches, known as sports. These can grow perfectly healthy foliage and flowers, but the color is different from the parent plant. You plant may have produced a shoot that is a sport.
Another possibility: Butterfly bushes are not long lived shrubs. However, they will seed themselves (sometimes, too much). The seedling's color often varies from that of the parent plant. A seedling could have sprung up at the base of your original plant and, as the original plant has gotten older and less vigorous, the new (white) seedling predominates.