Butterfly Bush Root System

Butterfly bush is a survivor, largely because of its root system.

Originally from China, Buddleia davidii or butterfly bush and its many cultivars have become standards in many U.S. gardens because of their graceful, arched stems and large, cone-shaped flower clusters so attractive to butterflies and other beneficial insects. The root system of the fast-growing butterfly bush is a fibrous web of roots that can adapt to a wide variety of environmental circumstances. Butterfly bushes thrive in moist, well-drained soil and are very cold hardy. The butterfly bush is a tough plant too, because of its root system, though too little or too much water can cause damage.

Characteristics

Butterfly bush has a fairly extensive web of roots adapted to drawing both physical plant support and moisture from the top foot or so of soil. In colder climates, above-ground branches and stems die back to the ground in winter. But the following spring plants vigorously re-sprout from the crown, the point where roots meet stems. Stimulating this annual dieback---cutting butterfly bushes back to within 12 inches of the ground---each spring actually supports vigorous stems and flower growth. Don't prune in fall or winter.

Advantages

Its fibrous, flexible root system makes the butterfly bush very adaptable. The butterfly bush is able to take full advantage of available water and nutrients. Its root system makes it more adaptable to space limitations, too, compared to many other flowering shrubs. Butterfly bush can be planted where other large plants would create problems. Because it lacks aggressive, probing roots, you can plant butterfly bush next to a building, sidewalk or driveway without worrying that it will damage such structures.

Disadvantages

Butterfly bush has less root mass compared to other shrubs, so it needs time to get established to survive winter stress. Plant new butterfly bushes early in spring or summer to allow the plants to establish a strong root system. The vast, fairly superficial root system also requires adequate moisture; the plants aren't very drought resistant. Well-drained soil is crucial because too much moisture or standing water can cause roots to rot, killing the plant.

Transplant Success

Even established butterfly bush roots can be successfully transplanted, in part because of the flexible, fairly superficial root system. Unlike shrubs and small trees that send a taproot deep into the soil to "tap" underground water sources, the butterfly bush is easier to dig up and move without damaging the plant. In mild climates, transplant either in spring or fall. In colder areas, transplant plants in early spring, before new growth starts. If a butterfly must be moved otherwise, transplant it as soon as it goes dormant, when the tops die back.

Rooted Stems

Butterfly bush roots easily on both new and woody stems, making it easy to create new, identical plants from favorite garden specimens. But this same trait has supported the invasive or unwanted spread of Buddleia davidii into natural areas. In places including the Pacific Northwest it is considered a noxious weed. Gardeners should clean up all B. davidii cuttings and clippings and throw them away---don't compost, because they root so easily---and dispose of spent flowers and dead seedheads. Cultivars derived from the original imported Chinese species are less likely to spread, but take precautions anyway.

References

• Clemson University Extension: Butterfly Bush
• Oregon State University Extension: How to keep butterfly bush from spreading noxiously

Resources

• Brian's Garden: Transplant a Butterfly Bush & Butterfly Bush Propagation
• Biologyreference: Roots