Link for My Latest Published Article on “Invasive" Plants
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| When people like nonnative plants, they don’t complain about how far and wide they spread. At a facility near the University of Virginia in Charlottesville, alien crocuses have spread throughout the lawn over the course of decades. Would anyone ever refer to these flowers as “invasive”? Probably not, because they create such a lovely sight. |
ALL TEXT AND PHOTOS © Marlene A. Condon
On July 12, 2024, The Daily Progress (the daily newspaper of Charlottesville, VA) published my article regarding the value to wildlife of so-called invasive species, such as the Mimosa-tree (Albizia julibrissin). You can find it at the link below, where half a dozen photos make clear the reason for the spread of naturalized plants (now usually referred to as “invasive”) as well as provide examples of some of the wildlife that makes extensive use of the alien Mimosa.
If you can’t access my article at this site, I am reproducing it below for your convenience.
Sincerely,
Marlene
Exotic Mimosa-tree Provides Food and Beauty
You’ve probably noticed the tropical-looking trees with gorgeous pink puffs of flowers that are currently blooming around the area. Known as the Silktree (or Silk Tree), Mimosa-tree, or just Mimosa (Albizia julibrissin), it presents a sight that most folks enjoy viewing, but others do not because they consider this nonnative tree “invasive”. But is it? Not at all; it’s “naturalized”.
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| Untended areas, such as the one in this photo, serve as important food sources for our native wildlife trying to eke out a living in urban areas. Here, a blooming Mimosa-tree helps to ameliorate the pollinator food-desert resulting from the nearby native trees having long since flowered. |
The lovely blooms and fern-like leaves of the tropical-looking Mimosa-tree provide landscape color at a time of year when it’s hard to find a native tree blooming. |
If you’re a gardener who has lived long enough, you’ll recall that decades ago, plants that became established and survived on their own, able to spread in a region where they were not indigenous, were considered wonderful additions to the landscape. You got more plants for free and more beauty to savor in your surroundings.
Even today, some plant
catalogs tout naturalizing: “For a carefree, colourful display year after year,
let your bulbs go wild! Flowering bulbs will keep your garden ablaze with
colour when other plants are just emerging or have faded. Naturalizing is the
process of imitating nature with bulb plantings.”
https://www.brecks.com/how_to_landscaping_with_bulbs_naturalizing
Note the final sentence that imparts the wisdom that
“naturalizing is the process of imitating nature”. This statement reveals recognition
of the fact that plants spread when conditions suit them in the natural
world. In other words, what folks today refer to as invasiveness is a
misreading of a natural process that is neither mysterious nor mystical, nor
hard to understand.
Old books don’t complain about “invasiveness”; to the
contrary, they treat naturalization as the normal—and often desired—outcome it
is for some alien-plant species.
My 1988 Peterson Field Guide to Trees tells the
reader that Mimosa is “[n]ative to S[outh] Asia but widely planted and
naturalized in the eastern U.S.” My 1983 Illustrated Book of Trees
informs us that “[the Silktree] has become extensively naturalized from
Virginia southward and often grows by the wayside.”
The latter book points out that Mimosa “is able to
thrive on even the poorer soils”. My 1980 book, The Audubon Society Field
Guide to North American Trees, concurs. It tells us this tree occurs in “[o]pen
areas including wasteland and dry gravelly soils.” And the 1981 University
Press of Virginia book, Trees and Shrubs of Virginia, adds “[w]ood
borders, clearings, [and] roadsides”.
What do each of these locations have in common? Every
single one of them results from people having impacted the soil at some point
in a site’s history. Otherwise, the area would be filled with old-growth trees,
the original landscape of eastern North America.
A 1998 Timber Press book, Trees of the Central
Hardwood Forests, makes the mistake of telling the reader that the value of
Mimosa is “[n]ot significant to any native wildlife species”. Indeed,
this declaration has been much used by people, such as activist-entomologist
Doug Tallamy, to disparage plants they view as alien invasives in need of
removal. But I must beg to differ.
In 2019, I had the opportunity to document the life in
the canopy (the upper layer of a mature tree) of a Mimosa. I had noticed this
plant growing alongside a bridge I have crossed numerous times while
exercising. As Mimosas are fast-growing trees, it didn’t take many years for
this one to get large enough to bloom at the level of the bridge where I could
observe the goings-on.
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| A day-flying Hummingbird Clearwing moth(Hemaris thysbe) is happy to feed upon nectar from a Mimosa-tree bloom. |
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| In addition to this Spicebush Swallowtail butterfly (Papillo Troilus), you could see a Tiger Swallowtail (Papillo glaucus) and Silver-spotted Skipper (Epargyreus clarus), as well as small bees, obtaining nectar from Mimosa-tree blooms. |
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This large,
healthy caterpillar was probably close to pupating after feeding upon the
leaves (still closed here in early morning) of this nonnative Mimosa-tree. |
Hummingbirds, small bees, several species of butterflies, a day-flying moth, and even caterpillars were getting food, courtesy of this foreign tree. Obviously, these animals could get food from native plants, if the appropriate plants existed nearby—and there’s the catch.
People seem to think “invasive” plants have stolen
space from native plants that could be growing there, but most native plants can’t
survive in the degraded soil where you typically find the nonnative plants designated
as “invasive”.
I’ve found that what’s true for the Mimosa is also
true of the many other so-called invasive plants that I’ve studied. The
wildlife value of these plants is, without a doubt, certainly of significance
when you consider that we are living in a world where development—that robs
wildlife of habitat and destroys the soil profile for most native plants—never
seems to end.
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| When people come upon “invasive” plants filling an area, they don’t consider its prior history of native-plant removal and soil damage that inevitably invited alien plants to grow there. The notion of “invasiveness” developed out of context to this bigger picture; without taking the whole story (i.e., background) into account, it’s easy to misinterpret the result. |
Additional attributes of the so-called invasive plants—including Mimosa—is that they can withstand drought and often are tolerant of pollution, whether it be in the air or the soil.
Thanks to climate change, drought has become a
more-frequent occurrence that can kill plants. (Along the river near where I
live, some species of large trees are seriously suffering right now, even some
located within the river!) Without drought-tolerant “invasive” plants, there
could come a time when little habitat will exist. All plants, native or not,
provide a living space for wildlife in some way.
In a 1989 conversation with PBS journalist Bill
Moyers, the novelist E. L. Doctorow, said, “When ideas go unexamined and
unchallenged for a long enough time, they become mythological and very, very
powerful. They create conformity. They intimidate.” His comments apply well to
the “invasive”-plant narrative.
Orville Wright pointed out that, “If we all worked on the assumption that what is accepted
as true is really true, there would be little hope of advance.” I would adjust this truism to read that, “If
we all work on the assumption that what is accepted as true about invasive
plants is really true, there is little hope of conserving our wildlife.”
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