By Dr. Leonard Perry
Extension Greenhouse and Nursery Crops
Specialist University of Vermont
The issue of native plants has been the
subject of quite a few articles and seminars these past
few years. The issue involves such questions as "What
is a native plant?" And, "How far should a
gardener go in planting natives to the exclusion of
non-natives?" One related concern that comes up
is that of invasive species--plants that aggressively
spread into areas they are not wanted, such as goutweed
by its roots, or the purple loosestrife by its seeds.
Invasive plants, once established, are
hard if sometimes practically impossible to eliminate
or eradicate. Often invasive plants crowd out other
more desirable plants, or even change habitats, as in
the case of purple loosestrife destroying wetlands.
As with many issues, there are people
on both ends of the spectrum although most are in the
middle. On the one extreme are those who believe all
non-native plants should be removed and only natives
planted instead. On the opposite end are individuals
who feel that this is a non-issue, and that beauty rulesplant
what looks nice, native or not. The definition of "native"
is itself a hotly debated current issue in gardening.
Most of us would like to use at least
some native species in our gardens so want to know more.
It's important to remember that both natives and non-natives
can have beneficial properties, such as attracting bees,
butterflies, and hummingbirds, as well as serving as
food sources for birds.
One definition of "native" refers
to plants that originally were growing in this country
when the first settlers arrived. A problem with this
definition is that what may be native in Georgia or
California may not be native here in New England, and
may, in fact, become a weedy nuisance. Plant ecologist
and owner of Prairie Nursery in Wisconsin, Neil Diboll,
has addressed this problem by defining natives both
in terms of location and time. He states that the problem
"isn't point of origin but rather behavior."
This brings us back to the invasive issue.
Some people argue that the problem with "exotics"
or non-native plants is that they are invasive. But
others make the point that so, too, are some of the
native plants, such as goldenrod. Many, if not most,
introduced or exotic plants in gardens behave quite
nicely, so the argument is, why should gardeners discard
Are you aware that many of our wildflowers
have been introduced and escaped to become "naturalized?"
Some were brought over by early settlers for specific
purposes, such as cattle feed or fiber. Others came
in as seeds on shoes, boats, and luggage.
You also need to keep in mind that plants
can be invasive either from spread of seeds or roots.
Invasiveness is itself a function of location. Many
plants listed as invasive don't behave this way in my
zone 4 garden. They either don't get enough heat or
long enough growing season to become a problem, or the
season is too short for them to set seeds (such as with
the Miscanthus grasses).
So what's all this mean to gardeners?
To me, one key point is that not all natives are good
and not all exotics are bad. It seems that a plant's
"bad" behavior, or in other words, its aggressive
or invasive habits, is what's not desired, and this
can be found in natives and non-natives. Diversity in
the landscape and the garden is what most gardeners
really want. As Diboll states, "diversity is the
ecologist's bias because to us diversity equals health
in an ecosystem."
Janet Marinelli of the Brooklyn Botanic
Garden is an author, editor, and champion of the gardener's
role in the preservation of the planet. She feels that
one day the native issue won't be an issue at all. "Someday,"
she believes, "we'll know enough about ecology
to be able to create totally new plant communities,
combining species from around the globe that add to,
rather than subtract from, the planet's wonderful variety
of life forms."
So it seems to me that a gardener's main
concern, before planting any "new" plants
in his or her garden, should be whether the plants will
get out of control in that particular climate and spread
through the surrounding natural landscape, especially
to the detriment of other plants. As a rule, gardeners
should be promoting diversity through their plant selections,
rather than monocultures. By paying attention to invasiveness
and diversity, and being so informed, gardeners will
be able to garden more responsibly.
If you want to study the issue further,
some good points were made in a recent article on the
Brooklyn Botanic Garden Website (http:// www.bbg.org/),
as well as in forum discussions on the GardenWeb Website