I love butterflies, and there is nothing better for drawing them into a yard than butterfly bush (Buddliea davidii). Unfortunately, butterfly bush is invasive. Solid stands have shown up on gravel bars in the McKenzie River, in clearcuts in SW Oregon, and on roadsides and waste areas elsewhere in the state. Butterfly bush is becoming the new Scotch broom.
The Oregon Department of Agriculture (ODA) did a risk assessment on butterfly bush a few years back and determined it was an environmental threat. Regulations were enacted to phase it out of the nursery industry. Today it is a B-rated noxious weed (bad, but too widespread to eradicate), and it is illegal to propagate or sell it in the state. It is not illegal to own one, but being a good citizen, I cut mine down and killed the stumps—reluctantly.
But the story isn’t over—in fact, it might be just beginning. Plant breeders are developing seedless varieties of butterfly bush, analogous to seedless grapes and seedless watermelons. ODA is working with Oregon State University (OSU) to develop a system to evaluate these new varieties to make sure they are non-invasive. We’ve drawn the line at requiring at least a 98% reduction in fertile seed production compared to traditional varieties under the same conditions. Two varieties have already been approved, ‘Asian Moon’ and ‘Blue Chip.’ More than a dozen others are in the pipeline. All of the new varieties submitted for evaluation thus far are inter-specific hybrids. Asian Moon, for example, is B. davidii X B. asiatica (Renfro et. al., 2007); it is a sterile triploid (3 sets of chromosomes).
Approved seedless varieties will be sold in Oregon as “Seedless Butterfly Bush.” I haven’t seen them for sale yet, but we’ve had lots of inquiries from nurseries, so I expect they will be available soon.
This week, Gary McAninch, the ODA Nursery Program Supervisor, and I met with the general manager of Ball Ornamentals. Their company has a number of other hybrid varieties in the pipeline. Some of them will probably meet the seedless standard, and some of them probably won’t; that will get sorted out in the weeks and months ahead.
The sea-change that we’re just beginning to see in the nursery industry is that ornamental plant breeders are considering invasiveness and working on breeding it out of not just butterfly bush but several other ornamentals that tend to escape from gardens. That’s good news, and from the pictures I’ve seen of the new hybrid butterfly bushes, there is more good news. The new hybrids are beautiful—less gangly and with larger more vibrant flower clusters, than the old varieties, and still attractive to butterflies and hummingbirds. I’ve got a feeling they are going very popular. I know I have a couple of spots in my garden where they would fit nicely—right next to some old invasive butterfly bush stumps.
Renfro, S.E., B.M. Burkett, B.L. Dunn, and J.T. Lindstrom. 2007. ‘Asian Moon’ Buddleja. HortScience 42(6):1486-1487.