Historically before settlement, we had a mosaic of plant communities in Wisconsin, each represented by myriad native species that evolved to be adapted to our climate, soils, topography, wetness and other site characteristics.
Hmmmm. Canada thistles and mean men the first invasives?
Early settlers unwittingly brought invasive plant seed, but also the means to expose soil to those invaders.
Point: some native species become/became invasive due to shifting influences of disturbances. For example, fire was often suppressed, which gave a competitive advantage to less or non-fire adapted species. i.e. prickly ash, which flourishes in old pastures, especially where fire is not allowed.
Habitat includes:ForestsField and forest marginsMeadows and prairieRight-of-waysFence rowsAlong waterwaysResidential landscapesOriental bittersweet is native to China, Japan, Korea, Mongolia, and the Russian Federation. It was introduced to the eastern US in the 1800s.Image of Oriental bittersweet climbing into the trees on the right and has pulled down the tree in front.
Both sexual (seed) and asexual (rhizome = root that sends up new shoots and stolon = root-like stem that sends up new shoots) reproduction. It can be difficult to identify individual plants due to clonal propagation.Oriental bittersweet is functionally diecious with separate male and female plants. Both male and female plants flower. Male flowers produce pollen that is received by female flowers. Pollinated by insects (bees) and wind.Birds aid the dissemination of seed by eating the fruit containing seed. The seed passes through the bird and can moved to uninfested areas. The seed germination rate is higher after the seed has passed through a bird.Seed viability in soil is not long (generally 1-3 years). A short-lived seedbank is helpful for long-term infestation control.Image of rhizome sending up new shootsImage of summer leaves and fruit.
People use the colorful fruiting vines for arrangements. Seed can be inadvertently dispersed when collecting, transporting, and disposing of the fruiting branches.
Although Oriental bittersweet is newly reported in MN, we can use assessments from the eastern and southern regions to prompt us into action before Oriental bittersweet is widespread. For example, Forest Service ranked Oriental bittersweet #5 of the top 10 invasive plant priorities for the Northeastern Area. Images: Oriental bittersweet vine girdling a tree (left) and a downed tree overwhelmed by bittersweet vines.
This mass of Oriental bittersweet vines climbed into the trees and is beginning to down trees.
When leafed out, Oriental bittersweet shades and smothers other vegetation. The images shows a Colorado blue spruce and fence engulfed by Oriental bittersweet.Infestation along Hwy 36 in the metro. Mn/DOT has controlled this infestation.
Identifying Oriental bittersweetTop left: Leaves are glossy green and leaf shape is highly variable Top right: Raised white bumps (lenticels) on the stemBottom left: Fruits are positioned at where the leaves attach to the stem (at the leaf axils). Green summer fruits are shown in this picture.Bottom right: Fall fruit with a bright yellow capsule.
Both American and Oriental bittersweet occur in the same habitat. Unfortunately, Oriental outcompetes American because it germinates better in the shade, has a longer period for photosynthesis because it leafs out early in the spring and holds its leaves late in the fall, and Oriental bittersweet can smother American bittersweet.Hybrids were created for a lab study demonstrating that the species can hybridize. Few viable progeny were produced from hybrids and hybrid pollen had a much lower viability compared to the species. Bittersweets with indeterminate characteristics (indicating hybrids) have been observed in the field.The nursery industry developed beautiful cultivars of American bittersweet that are a good choice for landscape use.
The easiest way to distinguish American and Oriental bittersweets is by the fruit capsule color (orange for American and yellow for Oriental) and fruit placement (at the terminal ends for American and at the leaf axils for Oriental).
Managing Invasive Woodland Plants
Today’s Outcomes• Know why species are invasive• Determine management goals• Understand range of management methods• Know integrated strategies
Early Vegetation From John T. Curtis, Vegetation of Wisconsin, 1959
Early Invasives?“Our waters filled with fish, and the air with gamebirds, and the rock ledges with rattlesnakes, andthe woods with large game…We have no Canadathistles or mean men.” Wm. H Canfield, 1842 Sauk County Surveyor
Invasive Beginnings Wisconsin Historical Society
Definitions“Invasive” definitions differ depending on the goal. “…causes economic harm to….” “interferes with land management goals…” “kills or displaces populations of native species…”
What makes a plant invasive?• Tolerate wide range of soil, light, other conditions• Enjoy longer growing period• Ability to alter soil chemistry• Prolific seed production• Have few or no natural controls
What do we do? Learn to ID and know plants’ biology Take inventory, map Create a plan Learn & use control methods Monitor & adapt
Grazing Principles similar tomowingGoats can be “trained”to some speciesRepeated treatmentsnecessaryContractors available
Girdle• Goal: starve roots• Good for clonal tree species. Photo courtesy of Tom Brock• Labor intensive. Photo courtesy: Tom Brock• Very effective if done correctly.• Timing: June-July best.• 1 or 2 step method.
Cut-Stem Treatment • Goal: kill plant Photo courtesy of Tom Brock • Good winter option • Very targeted use of herbicidesPhoto: Savanna Oaks Foundation, Inc
Cut-stem Control MethodTarget:• Shrubs/trees• buckthorn, honeysuckle, autumn olive, prickly ash, multi-flora rose, undesirable trees, etc.Herbicides:• Systemic• Active ingredients glyphosate (Roundup/generic) or triclopyr (Garlon 4/Element 4)
Cut-stem Control MethodTiming:• Summer, Fall or Winter preferred• Avoid early spring and deep snow periods• Above-freezing temps with glyphosate• Triclopyr (Garlon) at any temperature• Apply glyphosate within minutes of cutting.
Cut-stem Control MethodTechnique:• Cut stems at no higher than 6”.• Work in pairs, if possible, to avoid “escapes”.• Work in a pattern.• Treat only outer edge of larger stumps. Photo courtesy: Tom Brock
Prescribed Fire Requires training, experience Specialized equipment Good public relations Good neighbor relations Photo courtesy of Tom Brock Timing! Effective when integrated with other methods
Foliar herbicide• Safety first• Better for larger infestations• Selective vs. non-selective herbicides• Pre- vs. post-emergence application
Foliar herbicideTiming• Rosette stage best for biennials.• Before flowering, in general.• Combine with fire/mow.
Basal bark herbicide• Small; smooth bark• Generally, single-stem shrubs & trees• Treat all clone stems• Oil-based chemicals (triclopyr: Garlon 4 or Element 4) Photos courtesy of Tom Brock
Integrated Methods• Successful control efforts include: – Integrated approach – monitoring – early detection. Photos courtesy Tom Brock
Other Precautions• Clean boots to prevent seed spread (wheeled vehicles, too?).• Minimize soil disturbance.• Consider spread by wildlife & water.• Monitor imported materials (gravel, topsoil, mulch, etc).
Develop a management plan •Garlic mustard detected •Goal is to … Road
Develop a management plan Garlic mustard control 1. Develop a map 2. Satellite plants--goal to eradicate. 3. Extensive patch along road--goal to prevent further spread. Road
Example Plan• Satellite populations: – Pull 2nd year plants before flowering – Spray 1st year plants in fall or very early spring
Example Plan• Large patch along road/trail: – Mow, pull, spray along road before seed set. – Work perimeter inward • Spray rosettes fall/early spring • Pull escapes in between• Repeat, monitor, re-map subsequent years.
Volunteer OpportunitiesLearn while doing• Kickapoo Valley Woods Cooperative• The Prairie Enthusiasts• The Nature Conservancy
Other Resources• County Extension office – fyi.uwex.edu/weedsci• County DNR foresters – dnr.wi.gov/topic/ForestHealth/• Oaksavannas.org• www.ipaw.org
Summary• Early detection & prevention are critical• New species introduction & spread mostly dependent on our behavior• Set realistic goals• Make a plan, then adapt, using…• Integrated methods