INVASIVE SPECIES ERADICATION
Staff and volunteers of the
Kern River Preserve have spent over a decade
fighting invasive species. These efforts have
paid off with one of the most native forests in
western North America.
Each year staff of the Kern
River Preserve and partners spend many hours
eradicating invasive weeds from South Fork Valley lands.
Each of us can help prevent
the spread of invasive plants and animals. You
can help by learning which species can become
invasive and eradicate these from your own
yards. Help to educate your local nurseries
about the problem with invasives and get them to
stop selling problem plants. Contact your
legislator and local agriculture commissioner to
make sure no invasives are sold or promoted in
your county or town.
The article that follows is a
tutorial on purple loosestrife: one of a series
of articles staff of the Kern River Preserve are
preparing to educate about local invasives and
some steps each of us can take to help eradicate
Purple loosestrife (Lythrum
salicaria), a beautiful but aggressive
invader, arrived in eastern North America in the
early 1800’s. Plants were brought to North
America by settlers for their flower gardens.
Seeds arrived via European ships that used soil
as ballast to stabilize the vessel in rolling
seas. Since its introduction, purple loosestrife
has spread westward and can be found across much
of North America. Purple loosestrife grows an
impressive four to seven tall. It prolifically
invades wetlands and other moist areas. Each
mature plant produces 30 or more spikes and can
produce over 2.5 million seeds per year.
Leaves: Green, smooth,
lance-shaped, opposite/whorled, often downy
Stems: 4-sided and
woody (4-7 inch tall).
Purple-pink (5-7 petals), arranged in a dense
Season: Flowers mid
July to September
shorelines, roadside, drainage, and irrigation
ditches, to moist agricultural fields
Controlling the spread of
purple loosestrife is crucial to protecting
vital fish, wildlife and native plant habitat!
Purple loosestrife can easily spread if improper
control methods are used.
DIGGING & HAND PULLING
Pulling purple loosestrife by
hand is easiest when plants are young (up to two
years) or when in sand. Older plants have larger
roots that can be eased out with a garden fork.
Remove as much of the root system as possible,
because broken roots may sprout new plants.
Removing flowering spikes
will prevent this year’s seeds from producing
more plants in future years-- remember each
mature plant can produce over 2 million seeds
per year. At sites where plants have gone to
seed, remove all of the flowering spikes first
by bending them over a plastic bag and cutting
them off into the bag. Finally, cut the stems at
the ground to inhibit growth.
In areas of severe purple
loosestrife infestation, manual and chemical
control efforts are ineffective and may in fact
contribute to the problem. Bio-control works by
using a plant natural enemies against it. In
1992, five insect species which feed on purple
loosestrife in Europe were approved as
bio-control agents in North America.
You can read more about
biological controls at this website. California
Dept. of Agriculture Biological Control:
If an infestation is in a
dry, upland area, and on your own property, a
licensed pesticide applicator can apply an
approved herbicide to individual
plants by selective hand spraying. Broadcast
spraying is not recommended as it kills all
broad-leaved plants, leaving the area open to
further invasion from nearby sources of purple
loosestrife. This also provides an opportunity
for seeds present in the soil to sprout.
YOU CAN HELP
Ask your local garden center
or nursery to stop selling purple loosestrife
and its varieties (if you find it).
Horticultural varieties of purple loosestrife
were once thought to be sterile, but recent
studies have shown that this is untrue.
Landscape with native plants instead of purple
PROPER DISPOSAL of plant
material is important. Put all plant pieces in
plastic bags (vegetation rots quickly in
plastic) and take the bags to a sanitary
landfill site. Composting is not advised, as
purple loosestrife seeds may not be destroyed
and the thick, woody stem and roots take a long
time to decompose. Incineration is an effective
way to dispose of plant material.
BE AWARE that your clothes and equipment may
transport the small seeds to new areas.
Thoroughly brush off your clothes and equipment
before leaving the site.
KEEP SITE DISTURBANCE TO A
Wetlands provide habitat for
many native song birds, waterfowl, mammals,
amphibians, and fish which depend on native
wetland vegetation. Wetlands are also home to
many rare and delicate plants. Take care not to
trample or damage native vegetation when
controlling purple loosestrife.
Read more about Purple
Loosestrife and other invasive plants at the
Northern Prairie Wildlife Research Center