Download Purple Loosestrife - Langlade County, Wisconsin

Purple Loosestrife
Lythrum salicaria
Purple Loosestrife, a wetland perennial from
Europe, was introduced to the United States in
the 1800s as a medicinal herb, nectar plant for
honeybees, and garden plant. It also arrived
here unintentionally as a contaminant in ship
ballast. Free from the insects and diseases of its
homeland, Purple Loosestrife has a competitive
advantage over native wetland vegetation and is
now widely dispersed. It has spread rapidly in
the Midwest in recent years, threatening not
only native plant (including rare species) but
also the wildlife that depend on them for food
and shelter.
Once Purple Loosestrife is well established in
an area, it can overrun wetlands and eliminate
almost all other vegetation. Unfortunately,
Purple Loosestrife is still promoted by some
horticulturists for its beauty and by beekeepers
as a nectar source.
Twenty-four states, including Indiana, Iowa,
Minnesota, Missouri, Ohio, and Wisconsin,
have laws to discourage the spread of Purple
Loosestrife. In Wisconsin, for example, it is
illegal to sell, distribute, plant, or cultivate
Purple Loosestrife or any of it cultivars.
Purple Loosestrife is too pretty for its own good
Habitat: Moist soil to shallow water (established plants will
tolerate dry soil); sand to clay; sun to partial shade; can adjust to
a wide range of growing conditions including flooding in up to
18 inches of water ;sometimes planted in gardens where it
spreads to nearby wetlands, lakes, and rivers.
Height: 3-7 feet tall, or more.
Leaves: Simple; usually opposite on stems but sometimes
alternate or bunched in whorls; lance-shaped; without petioles;
edges are smooth; sometime downy.
Purple Loosestrife flower x7
Flowers: Showy; individual flowers have five or six
pink or rose-purple petals that are 0.50-0.75 inches
across and surround small, yellow center; closely
attached to the stem; bloom from the bottom of the
flower spike up to the top form early July to
September; plants can become quite large and several
years old before flowering begins.
Seeds: Borne in capsules that burst at maturity in late
July or August; main means of spread; single stems
can produce 100,000-300,000 seeds annually. Large
mature plants with fifty or more stems can release two
million seeds each year; survival rate is 60-70%
resulting in an extensive seed bank that remains
viable for twenty years; can live twenty months
submerged in water; most fall near parent plant;
water, animal, boats, and humans assist in
transporting them long distanced; disturbances such
as reduced water levels, damaged vegetation, or
exposed soil increase germination; sterile hybrids sold
by nurseries can pollinate wild loosestrife to produce
viable seeds.
Purple Loosestrife can grow to heights of
7 feet or more
Stems: 1-50 per plant; upright; stiff; usually foursided (occasionally five or six sided); green to purple;
often branching, making the plant bushy in appearance; somewhat woody; die back each
year; clipped, trample, or buried stems may produce new shoots and roots.
Similar Species: Garden Loosestrife (Lythrum vulgaris) is
also an escaped nonnative purple loosestrife, but not
nearly as invasive. Both may be confused with the native
wing-angled loosestrife (Lythrum alatum) that is found in
moist prairies and wet meadows. Native loosestrife has
winged, square stems and solitary flower sin the leaf
axils; lowers leaves are paired, upper leaves alternate;
generally a smaller plant than Purple Loosestrife. Purple
Loosestrife is also sometimes confused with Fireweed
(Ephiobium angustifolium), Blazing stars (Liatris spp.),
and Lesser Purple Fringed Orchid (Plantanthera
psycodes). See photos at end of report.
Purple Loosestrife flowers out of its axils
Control: Prevention is the most important element of
Purple Loosestrife control. Plants in gardens should be removed.
Wetlands should be checked annually for the presence of loosestrife,
especially in July when flowering begins and plants are easy to spot.
Ideally, since plants do not all flower at the same time, sites should be
A wetland with lots of
Purple Loosestrife is
soon a wetland with
little wildlife.
patrolled three times during the growing season, at one-month intervals
after flowering begins. Isolated small colonies, especially in areas
otherwise free of loosestrife, should be targeted for control first. Clean
boots, shoe, and clothing carefully before leaving infested areas. Rinse all
equipment, including boats and trailers, to prevent the spread of seeds.
If you can positively identify Purple Loosestrife, it is a good idea
to start a control effort early in the growing season because plants may
hold viable seed once flowering begins. Be careful not to leave loosestrife
stems or cutting behind since they can root or continue seed development.
Control efforts should e completed before the earliest flower, those lowest
on the stems, disperse seeds. Follow-up control is critical for at least three
years.
Manual or Mechanical Control: Small plants can be hand pulled. Older
plants can be removed with a shovel, but avoid leaving behind any roots.
Use caution when pulling or digging since disturbing the soil may
encourage more seed germination. Removed plants parts should be
landfilled, dried, and burned, or buried deeply in an area that will not be
disturbed.
The only
creatures that eat
this tall
European flower
are European
beetles; as a
result the purple
plague has
overrun wetlands
in 42 states from
Maine to
California, filled
in open water
and pushed
several species
of rare
amphibians and
butterflies to the
brink.
Mowing is not recommended because it can spread
plant fragments and seeds, expose the seed bank to more
sunlight, and lead to further seed germination. For limited
control, cut budding stems at the base, and then bag them to
make sure that seed development or spread does not
occurred. Continue this process because the plants will
resprout. This method is of limited value because Purple
Loosestrife will continue to spread by its root system.
Chemical Control: If applying herbicides near open water,
a permit may be required. Check with the aquatic plant
coordinator at your local natural resources department to
see what kind of herbicide you may use. Some states, like
Minnesota, require posting “Purple Loosestrife Control
Site” signs along public waterways or wetlands to notify
anyone who may swim, fish, or boat in the area.
A selective herbicide control method involves
applying a solution of 30% a.i. glyphosate to the raw area
of freshly cut stems after the flowering portions have been
removed. Treat all stems in a clump. This is generally the
least destructive and most effective method of small
infestations.
A close up photo of Purple
Loosestrife flowers
Currently, glyphosate formulated for use over water is the most
commonly used chemical for killing Purple Loosestrife. Rodeo® is a
good choice. Hand-spraying individual plants should be done in July or
August. Use 1.5-3% a.i. glyphosate and an adjustable herbicide spray
nozzle that will minimize overspray to nontarget plants. About 25% of the
plants should be covered. Broadcast spraying of glyphosate is not
recommended since it will kill too many nontarget plants. After spraying
the herbicide, any Purple Loosestrife flower heads should be cut, bagged,
and removed from the site.
Another type of foliar herbicide application, known as “the bloody
glove technique” involves an absorbent cotton glove that has been sprayed
with 5% a.i. glyphosate. The applicator, who wears chemicalresistant gloves on both hands with the cotton glove over one of
them, works with another individual who cuts and bags the
flowering portion of the Purple Loosestrife plant. The applicator
then grabs the remaining plant with the treated glove about onethird the way down from the top and moves the herbicide laden
glove up the stem. In order to keep track of the treated areas, a dye
should be added to the herbicide before work begins. Workers also
wear chemical resistant clothing when performing the type of
application.
In its native
habitat, Purple
Loosestrife only
comprises 1-4%
of the native
vegetation, but in
North America,
densities of up to
80,000 stalks per
acre have been
recorded.
A 5% a.i. solution of triclopyr approved for aquatic
conditions can be mixed with water and sprayed on loosestrife
foliage. Unlike glyphosate, triclopyr will not harm monocots, such
as grasses, sedges, cattails, rushes, or reeds, when used according
to label directions.
Biological Control: Biological control is currently considered the
best option for large-scale control of heavy Purple Loosestrife
infestations. Research involving the use of several of its natural
insect enemies of Europe, especially Galerucella beetles, has been
encouraging. Most of these insects feed almost exclusively on
Purple Loosestrife and are little threat to native plants. Although
they may eat native loosestrife, they prefer t he exotic species. If
handled properly, one hundred beetles can multiply to as many as ten
thousand in just a few months. As the supply of Purple Loosestrife
plants is depleted, beetles die or move on in search of more
loosestrife.
Prevention, early detection, and control are still crucial in
limiting the impact of Purple Loosestrife. If resources are adequate,
and fast remedies are needed for small isolated populations of
loosestrife, it is often best of use traditional methods of control to
limit seed spread rather than waiting for beetle establishment. For
It is at once a beauty and a
beast. In its seductive purple
splendor, it spells death for
everything in its way. Purple
Loosestrife has no natural
predators in this country. It
displaces native plants species
(and consequently native
animals that rely on native
plants), is a poor filter of silt
and pollutants, and grows so
densely in wetlands that it
crowds out fish and
waterfowl.
more details on biological control, contact the
aquatic plant coordinator at your local natural
resourced department. Most Midwestern states
have programs that help people raise beetles for the
biological control of Purple Loosestrife. See North
American Purple Loosestrife control contacts at
http://misegrant.umich.edu/pp/nacontacts.htm
It is important to know the difference between Purple
Loosestrife and native wildflowers.
Fireweed: Epilobium angustifolium
The flowers of Fireweed are often
more pinkish and do not come out
of the leaf axils
Lesser Fringed Purple Orchid:
Platanthera psycodes
Notice the fringes on the bottom petals.
Dense Blazing star:
Liatris spicata
Dense Blazing stars
flowers do not come out
of its leafs axils