Glossy Buckthorn | Spotted Knapweed | Tartarian Honeysuckle |
Reed Canary GrassPurple Loosestrife
| Leafy Spurge | Mulitflora Rose
September 1999Sally Petrella M.S., Nicole Shutt
B.S., and Dick McNeill Ph.D.
non-native plants species are an increasing threat to native populations of
plants and animals. Exotic plant species introduced into favorable habitats can
reproduce in large numbers; their populations often literally explode. This is
primarily due to the fact that many non-native species are more aggressive and
adaptable because they have no natural predators and readily replace the native
plants. Recently, a large increase in certain species of exotic plants has been
noted in Seney National Wildlife Refuge (SNWR).
The Seney National Wildlife Refuge consists of more
than 95,000 acres and was established in 1935 for the production and protection
of migratory birds and other wildlife. The refuge is composed of a rich mosaic
of marsh, swamp, bog, grassland and forest, with nearly two-thirds wetlands.
In August 1999, SNWR's manager Mike Tansy discussed
the problem of invasive species in the refuge with Sally Petrella, Nicole Shutt,
and Dick McNeill and asked them to conduct a preliminary survey of the 4-6
exotic plant species that are thought to pose the biggest threat to the
Sally Petrella, M.S., is a recent graduate in
biology at the University of Michigan, and a biological intern at SNWR. Nicole
Shutt, B.S., is a recent graduate from the University of Michigan's School of
Natural Resources and Environment, and also interns at SNWR. Dick McNeill,
Ph.D., is a retired professor of ecology and curator of SNWR's
MethodsWe surveyed alongside all
driveable refuge roads (approximately 85 miles) and the Pine Ridge Nature Trail
(1.5 miles) to record the prevalence of seven target species: glossy buckthorn
(Rhamnus frangula), purple loosestrife (Lythrum salicara), spotted
knapweed (Centaurea maculosa), leafy spurge (Euphorbia esula),
tartarian honeysuckle (Lonicera tatarica), reed canary grass (Phalaris
arundinacea) and multiflora rose (Rosa multiflora). Nearly all of the
refuge roads are two track with a vegetational strip down the middle. Although
35 invasive exotic plants have been documented in Seney National Wildlife Refuge
(table 1), we limited the survey to the species that seem to pose the biggest
threats due to their aggressiveness and suitability to SNWR. Six of our target
species are considered Category One by Region 9 of the United States Forest
Service: they are highly invasive, invading natural habitats and replacing
native species. The last species, multiflora rose, is Category Two: moderately
invasive, it may replace natives but only locally (USFS 1998).
Surveys were done by slowly driving each road and
identifying the locations of the target species. Only 1-5% of the refuge's
eastern portion where roads are present was surveyed. Additionally, Creighton
Road, along the western border was surveyed. The western half of the refuge is
wilderness area with no roads, therefore the interior was not surveyed.
Locations were marked on a series of maps made using ArcView version 3.0a. All
surveys were completed between August 16 through August 26, 1999. Prior to the
survey, Dick McNeill traveled through the refuge and flagged many of the target
species. He also brought in specimens to ensure accurate identification of all
All of the target species except leafy spurge were
very visible at the time of the survey because they were either flowering or
fruiting. Leafy spurge was difficult to see because the flowers had dried and
the vegetation surrounding it had grown taller. We were only able to find this
plant based on reports from Dick McNeill and Mike Tansy, who had identified the
plant earlier in the season. Therefore, leafy spurge and the other surveyed
invasive species could be far more widespread than our data show.
Due to time constraints, we were unable to survey
the refuge beyond areas alongside and adjacent to the roads. Obviously, this
method is very biased. We recommend a more thorough survey be done in the
Results and Recommendations for each of the
Glossy buckthorn (also known as smooth buckthorn)
is a small tree or tall shrub, growing to 6 meters high and supporting an open
crown of low branches. Leaves are alternate, simple, entire and oval. The blades
are 3-7 cm long, glossy dark green above, lighter beneath, and have 8-9 pairs of
veins. Flowers are perfect, pale yellow five-petaled and inconspicuous, borne in
axillary clusters May through June. Plants are polygamous or dioecious. The
fruit is a yellow-green drupe that gradually turns red to black as it ripens
July through September. The drupe encloses 2-3 nutlike pits that contain the
seeds (Barnes and Wagner 1981).
Native to Eurasia, glossy buckthorn can invade
wetlands and out compete native vegetation outside of its native habitat.
Introduced as an ornamental shrub and first collected in Michigan in 1934,
glossy buckthorn tolerates some shade and grows quickly in almost any moist
habitat. Consuming a lot of water, an acre of buckthorn can reduce the water
table as much as a foot and a half (Devine 1999). It forms dense clones and
resprouts vigorously when cut. The plant leafs out earlier and retains its
leaves longer than other shrubs. This characteristic may aid in its
Buckthorn is often noted as a forage food for birds
and other wildlife but its berries and branches may be offering false promises
for birds. It is reported that the fruit has a laxative effect on birds (Voss
1985), passing through the digestive tract within 10 minutes (McGowan-Stinski,
personal communication). The pattern of young buckthorn seedlings in close
proximity to 2-3 year old fruiting trees supports this finding, but it is
doubtful that the birds receive much nutrition from buckthorn. Buckthorn may
also offer birds less in the way of a nesting structure. In a recent study,
robins nesting in buckthorn and honeysuckle were more likely to have their nests
predated due to lower nest heights caused by the absence of thorns, sturdy
branches, and reduced basal cover in these exotic species ( Schmidt and Whelan
ResultsGlossy buckthorn is densely
concentrated within a 1-2 mile radius surrounding the refuge headquarters and
Visitor Center. Additionally, scattered patches are found on B-1, D-1, and G-1
Pools along Marshland Wildlife Drive and along C-2 Pool. The densest stands of
buckthorn are found along the dike west of the Show Pools and it has spread east
past the refuge boundary in this area. Some stands are so dense that only
buckthorn is growing there.
The plant is mainly found along roads and dikes but
extends into the wetlands as far as 3 meters from the road on the eastern edge
of J-1 Pool and along the entrance road. Some islands in the Show Pools and
along the northern portion of the Pine Ridge Nature Trail have also been
colonized. Young plants are growing in forests near the trail. On September 2,
1999, Jack McGowan-Stinski from the Michigan Nature Conservancy toured some of
the most infested areas of the refuge and gave a hands on demonstration of the
methods the Nature Conservancy uses to remove buckthorn and other invasives.
Jack has been experimenting with various methods of removing glossy buckthorn
from a fen in Michigan's lower peninsula for the past five years.
Glossy Buckthorn Locations and Density, 1999.
RecommendationsWe recommend a massive
removal of all buckthorn from the refuge and from all adjacent non-refuge
property, beginning at the perimeter areas and moving inward to the most
infested areas. Treating the perimeter areas first will reduce the chance of
invasion farther into the refuge.
Jack McGowan-Stinski of the Michigan Nature
Conservancy has been successful in removing glossy buckthorn using the following
methods. Seedlings with a stem diameter of less than 1 cm in diameter can be
removed by hand pulling or burning with a propane torch. Larger plants should be
cut 6 inches above the ground and then treated with herbicide immediately
(within 5 minutes) following the cutting, applied by sponge applicator. Rodeo or
Accord, wetland-approved herbicides, should be used in wet areas, mixed with
water to a 13-14% active ingredient in the final mix. All treated areas should
be flagged and repeatedly checked and retreated for up to 5 years.
Spotted knapweed is an herbaceous biennial plant that
is intolerant to shade and has a stout taproot and purple to pink flowers. The
up to 2 cm thick stems are branched and grow up to 1 meter high. The basal
leaves are entire to pinnately parted and grow to 15 cm. The stem leaves are
pinnately divided. The flowers are pinkish-purple rays that grow singly at the
ends of branches. The involucral bracts are stiff and tipped with dark fringe
Brought from Eurasia as a contaminant in alfalfa
and clover seeds, spotted knapweed has several characteristics that allow it to
outcompete native plants. A deep taproot enables it to survive very dry
conditions. It thrives along roadsides and other open disturbed areas (USDA
1994). Quick early spring growth helps it to outcompete the native plants for
light and nutrients. Spotted knapweed is also extremely prolific. Each flower
produces 12-35 seeds. The seeds can stay dormant in the soil for 8-10 years.
Botanists even suspect that the plant secretes a chemical that inhibits growth
of surrounding vegetation (USDA 1994).
ResultsSpotted knapweed is
found to some extent along virtually every road, dike and trail in the refuge.
Large patches of it are also found in East Walsh Farm and Diversion Farm. The
plant seldom extends very far from the edge of the roads, trails or dikes.
Because of more competitive native plants, shade trees and bracken fern seem to
effectively limit its spread beyond the roads.
Spotted knapweed first entered the refuge sometime
in the 1980s but was not documented in the refuge until the 1995 Seney Annual
Narrative Report. It was probably brought in with contaminated gravel used on
refuge roads. Even today, gravel piles at the entrance to C-3 Pool and the
entrance to Subheadquarters contain many spotted knapweed plants.
knapweed is only found along roads, trails, dikes, and two hayfields, we
recommend controlling it by mowing in the early spring before it flowers.
Repeated mowing prior to flowering should reduce the seed production but will
have to become a long term regimen due to the longevity of the seeds. In
addition, all gravel piles must be sterilized or treated with herbicides prior
to spreading on the refuge if spotted knapweed is to be controlled.
(Lonicera tatarica)Tartarian honeysuckle is a deciduous
upright shrub that grows 2-5 m. tall and is intolerant to shade. The leaves are
egg-shaped, 2-3 cm long, opposite and short-stalked. The creamy white to pink or
crimson flowers are paired, tubular, and less than 3 cm long. They are borne
along the stem or in the leaf axis in early to late spring. The fruits are red
or orange and have many seeds (NPCI 1999).
Brought from Eurasia to be planted as ornamental
shrubs, exotic honeysuckles can rapidly form a dense shrub layer, crowding and
shading out native plants. They release toxic chemicals that prevent other plant
growth. Alien honeysuckles also compete with native plants for pollinators,
possibly reducing the seed set for native species (NPCI 1999).
ResultsTartarian honeysuckle surrounds
the refuge headquarters and Visitor Center roads. A few isolated plants are
found on the eastern section of Marshland Wildlife Drive.
Tartarian Honeysuckle Locations, 1999.
RecommendationsWe recommend manual
removal of all tartarian honeysuckle and treatment of stumps with herbicide.
Plants should be cut 6 inches above the ground and then treated with herbicide
immediately (within 5 minutes) following the cutting, applied by sponge
applicator. Rodeo or Accord, wetland-approved herbicides, should be used in wet
areas, mixed with water to a 13-14% active ingredient in the final mix. All
treated areas should be flagged and repeatedly checked and retreated for up to 5
(Euphorbia esula)Leafy spurge is an erect, branching
perennial herb that grows to a meter tall and is intolerant to shade. It has
smooth stems that contain a milky latex sap and showy yellow flower bracts. The
leaves are small oval to lance-shaped and somewhat frosted along the margin. The
first pair of leaves are opposite, later leaves are alternate (USFWS 1997). The
flowers are small and borne in greenish-yellow structures surrounded by yellow
bracts. While the yellow bracts open May through June, the actual flowers do not
develop until mid-June. Leafy spurge has vertical and horizontal roots that can
extend many feet underground and can form stems.
Brought in as a seed impurity from Europe in the
1800s, leafy spurge has become a serious pest in western U.S. rangelands where
it invades grassland habitat, forming beautiful fields of inedible vegetation.
In the same family as poinsettia, the stems and leaves contain a latex that is
toxic to most grazing mammals. Thousands of acres of rangeland have been lost to
leafy spurge; it reduces the productivity of grazing land by 50-75% (NPCI
Leafy spurge tolerates moist to dry conditions but
is especially aggressive under dry conditions and in disturbed areas. The
vertical root can reach 5 meters or more into the ground and the horizontal
roots can spread almost a meter per year. The roots secrete allelopathic
chemicals to reduce competition from other plants. One of the first plants to
emerge in spring, vegetative stems are produced from existing roots in late
April. The seeds have a high germination rate and are viable in the soil for up
to 7 years. The seed capsules are explosive, dispersing seeds up to 5 meters and
are also carried by water and wildlife (NPCI 1999).
ResultsLeafy spurge was found in two
patches in two isolated locations within the refuge. One patch is approximately
15 by 5 meters and is located on Marsh Creek Road, south of T-2 West and north
of Marsh Creek Pool. This patch is marked by a stake and flagging. The other
patch of approximately 2 dozen plants is located near the J-I spillway,
southeast of the bridge. Because the plant was not flowering and the native
goldenrod was much taller than the spurge at the time of our survey, we easily
could have overlooked other patches of leafy spurge.
Leafy Spurge Locations, 1999.
RecommendationsWe recommend immediate
manual removal of plants and entire root system and treatment with herbicides.
Leafy spurge is easier to control within the first two years of establishment,
before the root system is well-established (USFWS 1997). Follow-up will be
necessary to check for resprouts and seedlings. We also recommend a new survey
be done in mid-June, when the plant is flowering above other plants.
Loosestrife (Lythrum salicara)Purple loosestrife is an erect
herbaceous perennial of Eurasian origin. It grows up to 2 meters high, has a
four-angled stem, and opposite, entire lance-shaped leaves 3-10 cm long.
Brilliant purple flower spikes make this plant very obvious from mid-July to the
end of September. The flowers have 5-6 petals and grow in the axils of bracts or
leaves or are terminal (USFWS 1997).
Imported from Europe as a garden ornamental in the
1800s, purple loosestrife has overtaken many wetlands in Canada and the United
States, crowding out native species and eliminating open water habitat. Rapid
growth and an enormous reproductive capacity allow it to spread quickly. Each
mature plant produces 30 or more flowering stems and can produce over 2.5
million seeds per year. It can propagate vegetatively from root and stem
segments (USFWS 1997).
ResultsPurple loosestrife is
encroaching from south of the refuge and was discovered in the refuge for the
first time this season. The plant in the refuge was found along Marshland
Wildlife Drive, at the edge of C-1 Pool.
Outside of the refuge, purple loosestrife is
spreading, especially from the south. Two miles south of the refuge border, two
plants were found along High Water Truck Trail near Duck Creek. Three miles
south of the refuge boundary, plants were found alongside M-77, on the west side
of the road. Approximately 6.5 miles south of the southern boundary numerous
plants were found alongside Manistique River Road, beginning about 4 miles
southwest of the Mead Creek Campground, and increasing in abundance further
south. North of the refuge, one plant has routinely been found on the west side
of M-77, 1.5 miles north of the refuge boundary.
Purple loosestrife was first documented 30 miles
south of the refuge in 1989 (Annual Narrative 1989) and then found bordering the
refuge in 1991 (Annual Narrative 1991). Treatment with herbicide followed by
hand removal has slowed down the spread into the refuge.
Purple Loosestrife Locaitons, 1999.
RecommendationsWe recommend constant
vigilance and immediate removal of any purple loosestrife found within or near
the refuge. Extremely difficult to control once established, early detection and
prevention of loosestrife spread are the most effective defenses (USFWS 1997).
This will require cooperation from private and public landowners. Plants should
be removed before they go to seed and the entire plant including all roots and
root tips must be removed. Plant locations should be flagged and rechecked every
Reed Canary Grass
(Phalaris arundinacea)Reed canary grass is a tall coarse
perennial cool-season grass that grows 0.6-1.8 meters high. The stems are erect
and hairless. The leaf blades are flat and tapering, 8-25 cm long, 0.6-2 cm
wide, and often harsh on both surfaces. The single flowers bloom in dense
clusters form May to August. Initially flowers are green and purple and turn tan
as they ripen (Hutchinson 1999). The seeds are shiny brown with short hairs
(Wisconsin Cranberry Growers 1999).
Reed canary grass is native to North America, but a
Eurasian ecotype has been widely introduced. The Eurasian ecotype may be more
aggressive but it is almost impossible to distinguish it from the native grass.
Due its aggressive nature, hardiness, and rapid growth, reed canary grass can
replace native wetland and wet prairie species. It grows best in wet soils and
spreads by seed or rhizome. Rapid growth occurs in early spring, seeds ripen and
shatter in late June, and growth declines by mid-August (Hutchinson 1999).
ResultsReed canary grass is found to
date in one approximately 30-acre patch in the eastern part of the refuge,
between pools J-1 and G-1. Noted as a problem in the refuge's Weed Inventory
Surveys since 1997, this 30 acre patch is in a former wet meadow, contains few
other plant species, and may be expanding into the surrounding wetlands. The
grass may be growing in other locations in SNWR but it only appears to be
crowding out natives and expanding in this one location. It has been found in
the refuge as far back as 1940 when a specimen was collected from along I-1
Reed Canary Grass Locaitons, 1999.
RecommendationsWe recommend repeated
late spring or late autumn burning of the reed canary grass because it is
confined to one 30 acre area and seeds of native species are present in the soil
in and around it. Fire will allow native, fire-adapted species to compete
successfully and a prescribed burn is the recommended method for removing reed
canary grass (Hutchinson 1999). Hand removal is not feasible, herbicides are not
selective enough, and heavy machinery would not destroy the hearty underground
rhizomes. Annual burns may be necessary for 5-6 years. Seeding with native
grasses and forbs after reed canary grass has died or gone dormant can also
hasten the recovery of native species.
Multiflora rose is a perennial shrub intolerant to
shade characterized by long arching canes and flowers or fruits in a conspicuous
cluster. Leaves are divided into 5-11 sharply toothed leaflets with a pair of
fringed bracts at each leaf stalk base. The white, fragrant flowers are 2 cm
wide and begin blooming in May or June. The rose hip fruits are bright red and
form a conspicuous cluster that remains throughout the winter. These clusters
make multiflora rose easily distinguishable from native roses that bear their
fruits in clusters of 1-4 (NCPI 1999).
Imported from Japan in 1866, multiflora rose is an
aggressive, prolific plant that can form dense thickets that crowd out native
plants in the U.S. Intentionally planted for wildlife cover and as a barrier for
livestock and automobiles, multiflora rose lives up to its reputation as a
"living fence." It readily invades disturbed areas due to its high tolerance for
a variety of conditions. It can spread by seed and by forming new plants at the
tips of canes that touch the ground. The plentiful seeds (an average plant
produces a million seeds per year) remain viable in the soil for up to 20 years
and are readily dispersed by birds that enhance germination when the seed is
passed through their digestive tract (NCPI 1999).
ResultsMultiflora rose is found in
several scattered locations throughout the refuge. Large patches are found along
the roads around the headquarters, along the eastern edge of C-2 Pool, along the
southern edge of D-Pool, and along the southern edge of A-1 Pool. There are a
few scattered plants on the eastern edge of D-Pool and the western end of C-1
Mulitflora Rose Locaitons, 1999.
RecommendationsWe recommend cutting of
all plants 3-6 times per growing season for 2-4 years or treating them with
herbicides. High mortality of multiflora rose has been achieved in this way
(NCPI 1999). Plants should be flagged and rechecked due to the extreme longevity
of seeds in the soil. The colder climate of the upper peninsula may aid in
inhibiting the growth of some plants.
DiscussionThis preliminary survey
reveals a serious infestation of glossy buckthorn at SNWR and potentially severe
infestations by six other invasive exotic plants. Glossy buckthorn is replacing
native species all around the refuge headquarters and visitor center and is
marching into the wetlands, crowding out native fruit-bearing species like
highbush cranberry (Viburnum opulus), raspberry (Rosa strigosus),
arrow-wood (Viburnum dentatum), and nannyberry (Viburnum lentago).
Left unchecked, glossy buckthorn could completely overtake the wetlands,
lowering the water table and leaving little for the wildlife to eat. Ridding the
refuge of glossy buckthorn should be a top priority at SNWR.
Five other invasive plants at SNWR could
potentially pose severe problems for the refuge unless they are removed and
continually monitored. Leafy spurge, purple loosestrife, tartarian honeysuckle,
multiflora rose, and reed canary grass have posed severe problems elsewhere, yet
at SNWR, these are found only in a few locations. Immediate removal of these
plants and constant monitoring for any new plants is the best way to keep these
plants from ever becoming a problem. The battle against invasives is much easier
to win before a species becomes well-established.
Spotted knapweed poses a different sort of problem
at SNWR. While it is widespread along the roads, shade intolerance seems to keep
this species from moving past the roadsides. One exception is at two of the
refuge hayfields. If these hayfields are to be maintained as quality wildlife
habitat, spotted knapweed should be removed and replaced by competitive native
The majority of our recommendations involve manual
removal, treatment with herbicides, and burning. While we considered it, we
chose not to recommend biological control of these species. Biological control
of spotted knapweed and leafy spurge is popular but we feel traditional methods
(pulling, cutting, spraying) should be attempted first. Because the introduction
of more exotics to control invasives is so risky, and SNWR is only just
beginning to recognize and address the problem of invasive plants, all other
methods should be exhausted before using biological controls.
and W.H. Wagner. 1981. Michigan Trees. A Guide to the Trees of Michigan and
the Great Lakes Region. University of Michigan Press: Ann Arbor,
1999. Clear-cut Mission. Communities Unite to Free Native Landscapes from
the Grip of Invasive Species. The Nature Conservancy 49(4): 12-17.
1999. Vegetation Management Guideline. Reed Canary Grass (Phalaris
Conservation Initiative. Alien Plant Working Group. 1999.
and C.J. Whelan. Exotic Lonicera and Rhamnus Increase Songbird Nest
Predation: An Impetus for Ecological Restoration. In press.
Annual Narrative Reports. 1989, 1991, 1995. Seney National Wildlife Refuge.
United States Fish and Wildlife Service.
Department of Agriculture. 1994. Animal and Plant Health Inspection Service.
Program Aid Number 59.
Fish and Wildlife Service. 1997. Region 3 Weed Information Book.
Forest Service, Hiawatha National Forest, et al. 1998. Michigan's Upper
Peninsula Weeds. Collaborative brochure.
1972. Michigan Flora. A Guide to the Identification and Occurrence of the
Native and Naturalized Seed Plants of the State. Part I. Gymnosperms and
Monocots. Kingsport Press: Bloomfield Hills, Michigan.
1985. Michigan Flora. A Guide to the Identification and Occurrence of the
Native and Naturalized Seed Plants of the State. Part II. Dicots. Kingsport
Press: Bloomfield Hills, Michigan.
1996. Michigan Flora. A Guide to the Identification and Occurrence of the
Native and Naturalized Seed Plants of the State. Part III. Dicots Concluded.
Kingsport Press: Bloomfield Hills, Michigan.
1998. Invasive Plants, Changing the Landscape of America: Factbook.
Federal Interagency Committee for the Management of Noxious and Exotic Weeds
(FICMNEW): Washington, DC.
Cranberry Growers Association. 1999. Wisconsin Cranberry Weeds: Reed Canary
Table 1. Invasive exotic plants found on
Seney National Wildlife Refuge.
*Category one: highly invasive
**Category two: moderately invasive
Links to other invasive species
Fish & Wildlife Service Invasive Species ProgramInvasive Species in the Great Lakes RegionGreat Lakes Environment - U.S.E.P.ALandscaping with Native Plants - U.S.E.P.ANorth American Weed Management AssociationMichigan Invasive Plant Council
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The end of May is a great time to watch for warblers at the refuge. One of the best places to see warblers on the refuge is from the Pine Ridge Nature Trail.