Theme: Exploring Wild
and Native Plants
Weedbusters
Students Tackle the Purple Menace
"When my third graders asked a local naturalist to help them
identify wild plants growing on our school grounds, we never
imagined their query would lead to a long-term environmental
action project," reports Minneapolis, MN, teacher Sherri Rogers.
The lovely magenta plant gracing the cattail marsh on the school
campus turned out to be purple loosestrife: an invasive, non-native
plant that chokes out other vegetation needed by wildlife. After
dissecting the plants and estimating the number of tiny seeds
they produced (millions!), Sherri's students began to appreciate
that this plant is well adapted for survival. When they then
learned about the plants' impact on their wetland wildlife habitat,
students wondered what they could do to make a difference.
Beetle Battles
The school's naturalist partner suggested contacting a local
scientist who was researching ways to eradicate loosestrife.
After examining the school grounds and discussing the plant's
life cycle and the risks it poses, the scientist helped students
set up a controlled investigation that mirrored his own research.
They released loosestrife-eating beetles in experimental plots
of loosestrife, and left others alone as a control. "The kids
eagerly checked our plots through the summer and fall, and noticed
that the beetles were indeed taking a toll on the plants in
the experimental plot," says Sherri. Once it was clear that
the beetles were keeping the loosestrife in check, the class
worked with their partners to brainstorm how they could grow
loosestrife in the classroom GrowLab through the fall and winter.
Their goal was to investigate which conditions promote and hinder
loosestrife growth and to rear loosestrife-eating beetles that
could eventually squelch the weeds in the schoolyard.
With support from their partner, students collected loosestrife
seeds and dug up the plant's crowns to try to propagate it in
classroom GrowLabs. Pairs of students tested different germination
conditions for the seeds, tried growing some plants from roots,
then observed and recorded plant growth. When plants were 12
inches high, students generated ideas about other ways to damage
or kill the plants. They experimented by using environmentally
benign substances, such as salt and sugar solutions. "When students
discovered that salt water killed the plants, I shared that
the "real" science they had done was on target," explains Sherri.
Saltwater marshes are not plagued with loosestrife.
Return of the Natives
Later in the year, the class brought beetles they'd raised on
plants in a plastic wading pool into the experimental plots.
"We have begun to notice that as the beetles take care of the
loosestrife, the cattails and other plants and animals are starting
to return," says Sherri. But the class isn't assuming the problem
is solved. They continue to experiment with other methods of
eradicating the weed, she reports. In one section they've tried
cutting plants back to the roots; in another, they've removed
all of the seedheads. Students observe and keep track of the
growth of loosestrife and other plants in each area.
"The project and opportunity to work with real scientists has
provided some very tangible lessons about plant adaptations,
habitat needs, and more," says Sherri. "Just as important, students
have a growing confidence that they can make a difference and
help protect the environment by controlling this habitat-destroying
weed in the state," she adds. In fact, they've become local
experts of sorts. Other schools have tapped into their growing
expertise, they've published their research in an environmental
journal, and they plan to tout their successes on a school Web
site. Sherri invites educators interested in learning more about
this biological control project to contact her at Breck School,
123 Ottawa Ave. North., Minneapolis, MN 55427 or via e-mail
(sherri.rogers@breckschool.org).
Editor's Note: Twenty-six states now have loosestrife control
projects. If you're interested in learning more about what's
happening in your area with this or other invasive weeds, contact
your state Agency of Natural Resources or Fish and Wildlife
Service.
Are Natives Friendlier?
Sherri's students discovered that plants brought into a foreign
country (in the case of loosestrife, probably in the ballast
of ships from 19th-century Europe) can become so aggressive
that they crowd out native vegetation and threaten wildlife.
Loosestrife, for example, has amazing reproductive abilities,
and lacks natural predators in its "adopted" country. (A single
stalk may produce as many as 300,000 seeds, and the plant can
also reproduce quickly from stem or root segments!)
A plant that is considered native to an area, on the other
hand, has evolved in a region over time and developed complex,
interdependent relationships with other organisms. Some plants,
for instance, are dependent on nutrients made available by certain
types of local soil fungus. Some butterflies depend for survival
on toxic substances produced by local plants for protection.
Native plants will rarely overtake an area, since they're
kept in check by their relationships with other populations.
And not all introduced plants wreak havoc with the existing
ecosystem. Many plants that are not native to an area make fine
garden or landscape plants. While tomatoes may have originated
in South America, for instance, they've been bred to be so dependent
on human care, they are not likely to get out of control. But
some non-native plants, like purple loosestrife, become invasive
and destructive because they compete well and are not kept in
check by natural predators.
One way of preserving habitat health in schoolyard projects
is to try to plant or maintain as many native plants as possible.
They are better designed to meet regional wildlife needs and,
because they have adapted to local climatic conditions and soils,
they should be easier to maintain. Always try to obtain native
plants from local or regional sources, or start your own from
collected seeds of plants that are plentiful. Never dig up wild
plants unless you're rescuing them from a spot where they are
in danger of being destroyed, such as a construction site.
Author: Eve Pranis
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© 2008
National Gardening Association