Horticulture / Auagust

Some Buzz about Buddleia davidii    

By: Julie Barnes

In this midsummer month of August let’s talk about a
plant that has lots of pollinators buzzing. Often
referred to as “summer lilac” or butterfly bush, Buddleia
davidii offers a profusion of nodding panicle blossoms
crammed full of small, colorful, tubular fragrant
flowers. Butterflies, bees, and hummingbirds find them
to be irresistible from now into autumn. The blossom’s
sweet nectar is how Butterfly bush got its name as it
attracts a variety of North American butterflies such as
black swallowtail, eastern tiger swallowtail, great
spangled fritillary, monarch, painted lady, and western
checker-spot. Since this non-native plant was introduced here from China, it has very few pests and as a
bonus to many of us, deer resistance. Butterfly bush is relatively easy to grow in areas with full sun and welldrained
soil. After becoming established, this plant will eventually tolerate humidity, drought or poor soil
conditions. In certain areas of our country enduring qualities such as these make Buddleia davidii an invasive.
So, there is a great deal of humming, droning and murmuring going on. On the one hand, butterfly bushes
are beautiful, reliable and delectable to pollinators, but then, they also produce prolific amounts of seeds
that are easily dispersed by the wind along roadsides, trails, or fields becoming weeds due to their adaptable
nature to then compete with native vegetation.
The USDA lists 20 states along with British Columbia, and Puerto Rico where Buddleia davidii has
naturalized, escaping gardens to nearby natural areas. Once established it is difficult to remove as it crowds
out native vegetation essential to wildlife. Until 2011, the State of Oregon prohibited the entry, transport,
purchase, sale or propagation of butterfly bush. Then approval was granted to sterile hybrids producing two
percent or less of viable seed. However, plants can only be labelled as summer lilac, nectar bush or seedless
butterfly bush. With the exception of a few sterile cultivars, Buddleia davidii is barred from propagation,
release, display or sale in New Zealand and it is also listed as one of the top twenty weeds in Western
Europe. Butterfly bushes are NOT host plants to any native caterpillars. Too many native plant advocates,
butterfly bushes are considered to be unworthy of a place in a pollinator friendly garden because they
cannot stay where they are planted. Goldenrods, asters, or Joe -Pye Weed are a few of their suggestions for
the sustenance of hungry butterflies, native bees or other insects needed in the food chain.
Because butterfly bush only provides nectar to adult butterflies and is not a host plant to maintain their
life cycles, combining host plants such as Butterfly milkweed (Asclepias tuberosa), Sweet pepperbush (Clethra
alnifolia), Virginia sweetspire (Itea virginica), New York ironweed (Vemonia noveboracensis),or Common Ninebark
(Physocarpus opulifolius) are needed for the caterpillars. An interesting survey was taken in 2012 by the
National American Butterfly Association (NABA). “Is Butterfly Bush Right For You?” How is it used in
your Garden? The results were quite fascinating: Based on its invasiveness, or what was heard about its
invasiveness, a few did not use it. The remaining respondents used butterfly bush in some way, emphasizing
that in addition to it, they grew as many native food plants possible for butterfly reproduction. For
nectar sources, Lantana, milkweed and agastache were recommended as possible substitutes. Only a few
gardeners could provide a FULL season of nectar with all their plants, so the perfectly named butterfly
bush (Buddleia davidii) was considered unanimously to be the ‘butterfly magnet,” or preferred late summer
nectar source. Since its intrusive nature is due to a high volume of seed production, some serious
deadheading as the flowers start to fade is needed to minimize the spread of volunteers. If that is too large
of a commitment then another plant must be considered altogether. An awareness of the pervasiveness is a
step toward controlling the invasiveness of this beloved shrub.