Poison Oak and the Covert Sting


Greetings guys, gals, and non-binary pals! Welcome back to Botany After Dark! My name is Kate, and I will be your host for
this journey. Today, we venture to the oft traversed forest
floor, into the world, of Poison Oak. *cue intro music* Anyone who has been hiking or camping in western
North America has potentially encountered the Pacific or Western Poison Oak (Toxicodendron
diversilobum). The species’ range includes conifer and
mixed broadleaf forests, woodlands, grasslands, and chaparral biomes, and shares a genus with
poison ivy, and other poison sumac species. For the purposes of this episode, this is
the species of focus. The rarer Atlantic Poison Oak (Toxicodendron
pubescens) grows in similar environments, though as the name suggests, its species range
extends from New Jersey, down to Florida, and west to Louisiana and Arkansas. It is often confused for Poison Ivy, as is
its Pacific counterpart. Be aware that while similar, poison sumac
is from a different genus than other sumac species, just as poison oak or poison ivy
are different from their non-abrasive counterparts. This is largely due to poisonous varieties
being placed into their own, unique genus of Toxicodendron, literally translating to
“poison tree”. However, they are from the same plant family
of Anacardiaceae, known as the sumac or cashew family of plants. These species produce drupes, more commonly
known as stone fruits. Others in this classification are peaches,
plums, and the like. While Pacific poison oak has been sighted
from British Columbia, all the way down to Baja California, the plant’s main concentration
range is California. Depending on the plant’s age and environment,
it can exhibit vines or a shrub’s sturdy trunk. However, if growing as a winding vine, the
support tree or other structure may well be buried within the foliage, depending on the
length of time the vine has been growing. These vines or climbing shrubs are known for
both their irritating sting and their tendency to suffocate any host trees unlucky enough
to encounter them. It is important to note that while the support
trees may well suffer, it is not due to compounds within the plant, nor constriction. Rather, the mere presence of foreign foliage
over top of the tree’s leaves can significantly decrease the possibility of photosynthesis
if expansive enough. Similarly, sometimes the vine’s extra weight,
especially when combined with winter frost and snow, is enough to severely impact an
otherwise healthy tree’s continued growth. As previously stated, poison oak can take
several forms, depending on its growing conditions. If exposed to full sun, for example, it becomes
a bushy shrub, stable in its own right. However, if the same plant is grown under
a canopy, exposed to dappled sunlight, it is much more likely to become a climbing vine. This makes identification more tricky, though
not impossible. The general rule for this plant’s leaves
is that they always grow in clumps of three. However, depending on the growing conditions
and individual plant genetics, they can also appear in clumps of five or seven. Remember: regular oak leaves do not grow in
odd sets. They grow in sets of two. Also, though reminiscent of traditional oak
leaves, those of Toxicodendron species are not as deeply lobed, nor toothed, as those
of their non-irritating counterparts. Furthermore, the western species tends to
have glossy leaves, while the eastern has fuzzy leaves, with hairy or thorny stems. Both are generally one to four inches long,
and change from bronze in the spring, to green in summer, and pinkish-red in Autumn. Both also produce whitish berries, rather
than acorns. It is also notable that all plants with the
Toxicodendron genus are urushiol-bearing species. Oddly, while some people have severe, volatile
reactions as a direct result to exposure to these plant oils, others have none. It depends on individual body chemistry as
to the severity of such a response, but it is rare to be relatively unaffected. However, the urushiol present in this and
other Toxicodendron species often takes several hours to present a rash. If caught prior to such a dermatitis response
occurring, prevention is possible. One such preventative is Technu. It is a highly effective cleansing agent that
deactivates the urushiol you might have come into contact with, so long as it is used early
enough. Interestingly, a person’s response to these
compounds tends to worsen with exposure. This means that while the initial contact
may well be mild, any interaction thereafter may well become increasingly worse. The irritating oils are relatively manageable,
if aggravating… when contained within the plant. While most well-known for its topical properties,
these species are far more dangerous once the urushiol contained therein is released
as an arisol. The most common and easiest release mechanism
for said compounds is fire. With the prevalence of forest fires in California,
you can imagine that this would be highly problematic. Were someone caught in the midst of a fire,
where urushiol-bearing species are present, they would likely be in severe respiratory
distress within an incredibly short period of time. Not only would the smoke impair breathing
and the likely present carbon monoxide begin to prevent oxygen absorption, but as the plants
begin to burn, their irritants become airborne. According to accounts, many years ago, prior
to current safety and equipment regulations, often the only time firefighters wore respirators
was when poison oak was present and potentially burning. While Technu is highly effective against topical
irritation, there is no defense against inhalation. Lungs have a difficult enough time with dust
particles. The introduction of a substance that causes
a severe rash on generally durable surface skin to a structure comprised of bare mucous
membranes can be catastrophic. Exposure for even a short period of time could
prove fatal, as inhalation of the urushiol compounds is akin to having it directly injected
into your lungs. While some are relatively immune to topical
irritants, this is far more than the body can generally handle, causing even those with
no general reaction to fall incredibly ill after exposure to urushiol-laden smoke. That being said, while potentially highly
toxic and irritating for humans, Toxicodendron diversilobum is edible for many animals. It also often acts as a nurse plant for other
forest species, providing dappled cover for developing shoots. As such, if at all possible, leave plants
in situ when you find them Be careful as you navigate foot paths, dear
friends. Depending on where you are, you might well
run into poison oak, or one of its relatives, especially on less-maintained trails. Travel well. If you look in the episode description, there
are links to my blog and YouTube channel, where I talk more about plants, as well as
my Patreon and relevant social media links. To that end, I would like to thank Rob Nelson
for being a Patreon supporter. He runs Untamed Science, a channel discussing
and supporting biodiversity and conservation efforts, which is linked below. Also, if you would like to start your own
podcast, I would recommend Pinecast. It is the platform I am using and while I
have only been posting for a short time, creator support has been comprehensive and swift,
and the interface is easy to navigate. Though the service is free, that version only
allots for the upload and posting of 10 episodes at a time. If you do decide to upgrade, you can use coupon
code r-a19fe9 for 40% off for 4 months, and support Botany After Dark. To all my listeners at home, work, or somewhere
in between, thank you for tuning in. I’ll talk to you next week about Climate
Change and the very real and very destructive impact it is having on the planet. I’d tune in for that, if I were you. Have a good one. This is Kate, signing off.

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