The Production and Invasion of Buddleja davidii in Oregon

Julie Ream with Dr. James Altland

Butterfly bush worldwide

• Grows on old industrial sites and bomb sites in England

• Problem on river bars, floodplains, and forest plantations in New Zealand

• Thrives on interstate medians and rivers in Washington state

Butterfly bush in Oregon

• High value product in nursery, landscape, and retail garden industry

• B-listed as a noxious weed

Why butterfly bush was listed

• Very invasive in certain riparian areas

• Grows on many roads in Oregon

• As big a problem as scotch broom for some foresters

• Thrives where nothing else grows

My project goals

• To describe in detail the natural sites invaded by Buddleja davidii

• To determine nursery production practices that could limit or eliminate invasiveness

Natural sites: materials and methods

• Site selection:

-Planned to do 3-4 sites of each type (riparian, roadside, natural area, old industrial area) in each geographic region

-Geographic regions included Portland metro area, Coos Bay area, Oakridge area, and rural North Willamette Valley

Natural sites: materials and methods

• Marked out the area of each site using set guidelines

• Established 5 subplots per site for certain data questions

• Simply answered the other data questions

Natural sites: observations

• Grows everywhere from floodplains to mountain slopes

• Appears to be a pioneering species• Densest invasions were on burn sites and

regularly disturbed sites• Grows mostly in rocky and sandy soils, but

found some in clay soils• Herbicides control it if applied by hand

Natural sites: resultsOverall density of bushes vs. type of site

0

0.05

0.1

0.15

0.2

0.25

Natural Area Old Industrial Riparian Roadside

Total

Drop Page Fields Here

Average of Overall Density of Bushes (bushes/m2)

Type of Site

Drop More Series Fields Here

Natural sites: results

Density of immature bushes vs. % cover

0

0.1

0.2

0.3

0 20 40 60 80

Cover (%)

Den

sity

of

imm

atur

e bu

shes

(b

ushe

s/m

2)

Density of Immature Bushes(bushes/m2)

Nursery production: materials and methods

• Visited both retail (9) and production (10) nurseries

• Asked about management practices

• Looked for and collected escaped seedlings

Nursery production: observations

• Nurseries that did not cut back over winter had more escaped seedlings

• Loose cuttings rooted themselves

• Most nurseries with escapees were wholesale/production operations

Nursery production: results

• Determined that 37% of nurseries I visited had escaped seedlings

• Of those 37%, 71% were production nurseries

Nurseries with escaped seedlings (%)

37%

63%

Total % withescapees

Total % w/oescapees

More to be done

• Visit more nurseries and more natural sites

• Herbicide trials

• Seed tests

-when seeds are released

-how far wind blows seeds from mother plant

-if seeds need heat to germinate

Acknowledgements• HHMI Program• OAN and the Nursery

Industry• Dr. Mark Wilson of Botany

and Plant Pathology Dept.• Rod Jordan of Moore Mills

Timber Co.• Jim Carr of Menasha Forest

Products• Portland Parks and

Recreation

• Dr. James Altland of Horticulture Dept.

• Steve Wickham of Plum Creek Forest Products

• Wanda Crannell, BRR advisor

• Tim Butler and Glenn Miller of the ODA

• The Nature Conservancy• Bruce Kelpsas of Helena

Chemical Company