[MAIPC] T. radicans

[frazmo]

I frequently try to remind people that the term "invasive" should only be
applied to non-native plants that cause harm. Natives that annoy people
preferably should be called "agressive" or some term other than invasive.

Absolutely I agree with others that PI does not harm trees. And more than
once I have observed woodpeckers feeding on the berries in the winter -- an
important food resource. Also deer eat PI, not that that's necessarily a
plus!

Now on the climate point, there is some very interesting research that
suggests that higher CO2 levels increase viney growth. And in the case of
PI Dr. Lew Ziska found that levels of the toxic urushiol compound were
substantially higher when he raised CO2. As well, with warming, invasives
like kudzu appear to be doing better in our Mid-Atlantic climate. And I
would expect my nemesis English ivy to become a worsening problem in cooler
areas like central PA where colder winters once held it back. And Southern
invasive plants are steadily marching northward. As well as Burmese
Pythons. Sigh.

Cheers, Steve Young



On Mon, Apr 6, 2020, 10:48 AM Susan Gitlin <
susan.mclaughlin at alumni.stanford.edu> wrote:

> 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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