This beautiful but
invasive plant has incited controversy since the 1800’s when it was first
discovered on the East coast. Purple
Loosestrife, Lythrum salicaria, is native to Eurasia and in its native range
has several herbal uses. Whether it was
brought over deliberately for herbal or ornamental use, or arrived in the
ballast water of ships or as seeds in the wool of imported sheep we’ll never know.
Before Americans
became aware of the invasive nature of Purple Loosestrife, it was often used as
an ornamental plant. Purple loosestrife
is often used in water and bog gardens in Europe and is sold in garden
shops. And even here ornamental
selections are sometimes offered as garden plants. They are marketed as
sterile, but our ever wary evasion biologists warn that these plants are often
capable of producing seeds or crossing with wild plants.
In the 50’s conservationists
began to get alarmed over how fast Purple Loosestrife was spreading, and it was
thought, choking out native wetland plants and displacing food and habitat for
native birds, fish and other wetland creatures. Its bright color certainly
makes it obvious. Efforts were begun to control and eradicate Purple
Loosestrife.
As many a drive down
a country road with marshy edges will tell you, the efforts and millions of tax
payer dollars used to eradicate Purple Loosestrife haven’t been completely successful. However, in the 80’s Michigan developed the
Purple Loosestrife project, which enlisted the help of school children to help
eradicate the plants. Thousands of
imported Galerucella beetles of two species were released as well as a tiny
root weevil and a small insect that feeds on the flowers of Purple Loosestrife
and disrupts seed formation.
As with many
non-native plants once considered to be invasive, time often restores some
equilibrium to the environment. Today
it’s obvious that in many areas of Michigan those natural predators released
and changing conditions are controlling the weed. While clumps of Purple Loosestrife still
exist, the vast seas of purple that once clogged nearly every Michigan wetland
have largely disappeared.
Purple Loosestrife
prefers to grow in wet soil or shallow water in the sun. It has perennial roots that send up new
shoots each spring and each year the clump expands. The reddish stems grow to about 4 feet high
and are covered with pairs or whorls of long narrow leaves, which briefly turn
bright red in the fall. At the top of
the plant a spike of small magenta-purple flowers begins blooming in late June
in southern Michigan, somewhat later in northern areas and it may continue
blooming until frost.
It was once thought
that Purple Loosestrife spread by rhizomes (special roots), but current
research shows that spread of the plant is primarily by seeds. A mature Purple Loosestrife plant produces
millions of seeds and these float on water, get carried on beaks and feet of
water birds, or in the wool and fur of animals to new locations.
Purple Loosestrife
has some value as a food or habitat source for our native wetland species of
animals. Some butterflies and bees do
visit the flowers in wetland areas, including the monarch. Some bird species actually prefer purple
loosestrife areas, such as red winged blackbirds. The Wilson Ornithological Society published a
study that found at least 10 species of birds in Lake Huron wetlands utilized
purple loosestrife stands for nesting. The studies were done close to where I
live and I found them quite interesting. You can read that study here: https://sora.unm.edu/sites/default/files/journals/wilson/v111n01/p0105-p0114.pdf
The study found that
insects and other invertebrate prey for birds was similar in wetlands with and
without purple loosestrife and that the diversity and abundance of bird species
varied by the structure of the wetland plants – whether they were reeds and
grasses or shrubby for example – whether or not the species was purple
loosestrife or native plants.
My take after
examining studies and personal observation is that purple loosestrife is not as
bad as some native plant purists would suggest. While it is pretty its growth
shouldn’t be encouraged and gardeners should not deliberately plant purple
loosestrife in the landscape. Whether
you want to wage war with it in wet areas of your property should it pop up on
its own is really your choice.
I have had purple
loosestrife in my large pond for more than 5 years. It started as a single plant. There are now 3 plants in the pond. And ponds close by don’t seem to have any of
it. I don’t know how it got there but I
am not going to worry too much about it.
Not all people share my idea that nature knows best- some people get
very excited when they spot purple loosestrife and will pester you to remove
it. If that kind of thing bothers you then by all means yank it out should it
come to your place.
While it’s doubtful
we will ever totally eliminate Purple Loosestrife, discouraging ornamental use
should keep Purple Loosestrife to isolated and much more appreciated clumps of
vivid color along the roads and wetland edges.
Once again already disturbed areas such as ditches near farm fields,
polluted water and gravely wet soil along roads favor this plant over native plants,
but nature chooses plants best suited for the conditions, whether they are
native or not. To have something pretty
growing in these areas which pollinators and birds can utilize may be a bonus.
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