[MAIPC] T. radicans

[Susan Gitlin]

Thanks to everyone!

Yes, I am of course aware that poison ivy is native and that a native plant
belongs to an ecosystem and therefore does not cause ecological harm.   I
have discussions with people about the distinction between "aggressive" and
"invasive" on a daily basis.  I'm with you!!!!!

However, the Federal definition for invasive plants does allow for harm to
human health.  Moreover, noxious weed lists stem from agricultural concerns
more so than from ecological ones.   I was mistaken in thinking that poison
ivy is listed in Virginia as a noxious weed.  I had thought that I had seen
it listed there previously, but it is not.  As far as I can tell, it is
only listed in Wisconsin.  https://plants.usda.gov/java/noxComposite

But this person indicated that she had seen it as an "invasive native" on a
Virginia Forestry list.  I would love to argue with the writer of that
list, but I can't find it!  In any case, because she said she had seen it
taking over trees, I was wondering whether it had increased in robustness
(to use the term that Faith used).

>From the responses that I have received thus far, it seems that no one has
seen T. radicans take over trees to the extent that my "informant"
suggested.

Thank you very much for your feedback!

--Susan

On Mon, Apr 6, 2020 at 10:32 AM Atha, Daniel <datha at nybg.org> wrote:

> Dear Susan,
>
> I have botanized in the US for thirty years and I have often marveled at
> how Poison Ivy will climb a tree, spread its long, but limited lateral
> branches, but not kill the tree.
>
> Yes, it can be aggressive and form large stands, but these almost always
> form after significant disturbance by humans or the rare natural
> disturbance like fire, landslide, flood or blowdown.  Yes it can climb a
> tree and appear to “smother” it.  What it does is climb weakened trees with
> already reduced canopies.   It does not climb from tree to tree in the
> canopy and break down a forest limb by limb until there is no forest left.
> That is what Kudzu, Porcelainberry, Bittersweet, Japanese Honeysuckle and
> other invasive vines do.  Vines that were brought here by humans and that
> have no natural checks and no value for wildlife.
>
> Poison Ivy is native to North America.   Numerous birds and mammals
> evolved over millennia to depend on its abundant crop of fruit high in fat
> and other nutrients needed for migration and winter survival.
>
> Yes, Poison Ivy causes contact dermatitis in humans.   People should learn
> to stay away from it.
>
> Haven’t we humans already destroyed enough of the planet?  Must we destroy
> a species of plant just because we can’t figure out how to avoid it and in
> the process imperil countless insects, birds and other wildlife?
>
> Best wishes,
>
> Daniel Atha
> Botanist
>
>
>
>
>
>
>
> Sent from mobile device
>
> On Apr 6, 2020, at 9:36 AM, Susan Gitlin <
> susan.mclaughlin at alumni.stanford.edu> wrote:
>
>
>
> [*External E-Mail*: Verify source before clicking on any links or opening
> any attachments.]
> Hello, folks.
>
> I know that poison ivy is a noxious weed, but I believed that was because
> of harm to human health.  I was not aware that it behaved as an invasive
> vine, smothering trees a la English ivy.  That would not make sense to me,
> except in rare cases, because in that case our local ecosystems would have
> far fewer trees.
>
> However, someone today told me that poison ivy smothers and kills trees.
> Has this always been the case, or is it now happening due to increased
> carbon dioxide in the air?  If the latter, is climate change converting our
> native plants into plants that cause ecological harm?
>
> If you could share your knowledge on this, I'd appreciate it.
>
> Thank you!
>
> --Susan
>
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