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Poison Oak

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Poison Oak

Postby markskor » Fri Jun 30, 2006 11:01 am

Just for the hell of it, did some research, I wanted to check my own personal knowledge of altitude habitat…I still say it seldom grows above 3000 ft…4000 tops, but…

After a few google hours…

Western poison oak (Toxicodendron diversilobum, Anacardiaceae) - Previously divided into one species called either Rhus Toxicodendron, Rhus quercifolia, Rhus lobata, or Rhus diversilobum. Currently in the Toxicodendron genus - Toxicodendron diversilobum; bush or climbing shrub; west coast US and British Columbia

Poison Oak or western poison oak is native to western North America, with a distribution extending from British Columbia south to the Baja California peninsula. In Washington and Oregon, poison oak- found mainly in the western regions of the states. This western variety found strictly on the Pacific Coast from Southern British Columbia to Baha California. Its range stopped by the deserts and the Sierra and Cascade Mountain ranges to the east and by the Pacific on the west.
The western variety - discovered by the prolific botanist David Douglas (1799-1834) on Vancouver Island, Canada in 1830. (The Douglas Fir and Phrynosoma douglassi, the Short-horned Lizard, named after him.)
Early Spanish settlers from Mexico called it "yiedra," Spanish for ivy (from the Latin word, "hedra"). Soon "maligna" added to the name, for this was truly an "evil weed." (Toxicodendrons)

In California, the number of working hours lost because of dermatitis caused by poison oak makes it the most hazardous plant in the state.
Poison oak is very resourceful and versatile. Its range extends from sea level to 4000 feet. The soils it prefers are dry, but it can also adjust to living in moist environments. It grows especially well in areas where the ground has been disturbed such as forest trails, city parks, suburban backyards, and roadside embankments (Hauser 2001). Essentially, poison oak is not limited to particular soils or drainage patterns. It does opt for sunnier locations, but the adroit plant can dwell in shady or non-direct sun areas. In vine form, poison oak might kill its support plant by smothering or breaking it due to its opportunistic stem and root system (Harris & Howard 1994). (Toxicodendrons, 1)
However, another source says - In California, it is widespread and grows in a wide range of habitats from sea level to the 5000-foot elevation, including open woodland, grassy hillsides, coniferous forests, and open chaparral. (Poison Oak, 1)
Although 50% of the population is clinically sensitive to poison oak and poison ivy, about 75 to 85% can potentially develop an allergy if exposed to a sufficiently high concentration of the toxin. The oil in the plants, its called arusiol, and it is an almost invisible -- well, it is invisible to us in the quantities that we would see it in. A very clear, thin oil flows in canals in all parts of the plant. When something breaks the canals such as a broken leaf or even an insect bite, the arusiol comes out, sits on the leaf, and waits for a human to pass by, and when it gets on our skin 85% of us will have an allergic reaction after our first exposure. As with most allergic reactions, you have to have a sensitizing exposure. Then the next exposure, the body decides that this allergen is dangerous and goes after it.
Once a reaction to the toxin has occurred, the body responds with a cell-mediated immunity, which is a delayed hypersensitivity. Those individuals who have developed delayed hypersensitivity are sensitive to the toxin and repeated exposures further increase sensitivity. Conversely, long periods with no exposure will reduce an individual’s susceptibility to the allergen.

Work cited:
• The Biogeography of Toxicodendron diversilobum or Western poison oak: San Francisco State – Department of Geography: by Emily Meriam, 316, Fall 2001 See: http://bss.sfsu.edu/holzman/courses/Fal ... ebsite.htm
• The Toxicodendrons: See: http://ops.tamu.edu/x075bb/caddo/frameidx.html
• Poison Oak, Integrated Pest Management for Home Gardeners and Landscape Professionals: See: ... clnk&cd=18
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Postby rightstar76 » Fri Jun 30, 2006 1:23 pm

You don't want to get this. I am extremely careful when hiking not to touch it. In fact, I avoid trails that are covered with it. Recently, I was hiking a narrow trail and there was a section with poison oak. It was too late for me to turn around as I had covered a significant distance. I walked very slowly and thought I had succeeded in not making contact. Somehow my right elbow touched it which is why 3 days later I came down with an itchy rash. I won't be hiking that trail anytime soon.
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Postby copeg » Fri Jun 30, 2006 1:43 pm

I hate poison oak. Gotten it too many times. Thanks for posting all the info Markskor. Last weekend in Big Sur I was walking at a snails pace to avoid the poison oak. Washed up when I got back to the vehicle. I expected to get a rash but it just never happened.

There are treatments you can use a) before - prevents urushiol from absorbing in your skin and supposedly inactivates it and b) a soap to remove after contact. I've never used these but after last weekend, will invest next time I plan on hiking where this plant grows.
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Postby Allyn » Fri Jun 30, 2006 5:34 pm

Years and years ago in the SF Bay Area we used to ride what are now called mountain bikes, but back then called balloney bikes due to the 2.125 size tires. You know the ones with the single speed and kick back brakes? Well we used to ride them through the hills and trails on the east side of the bay in Berkeley and El Cerrito. We had a local trail I was clearing in the winter and the brush I was cutting and sweating all about was poison oak! I was rubbing it all over without knowing about it because there were no leaves. Well the next few days told the story! I had P.O. everywhere (well almost everwhere for a male! say 85% of my body :unibrow: ). Anyway, to this day some 30 years later, I can rub up against it but won't get it. I will not try and see if I am totally immune, but it was was sure fire way of getting rid it for quite some time ever again! My future wife (who I had met only 3 weeks earlier) was somewhat skeptical of my excuse for not being able to go out on a date with her!
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Postby Kerstin » Sun Jul 23, 2006 12:49 pm

Poison oak....shudder!

As a teenager in the 1980's, I rockclimbed a lot. On some approaches to various climbs, we had to bushwhack through areas that had a lot of poison oak. While I'd do my best to avoid the plant, I know I made contact with it. I never got a rash. I thought I was immune.

Before I moved to South Lake Tahoe I lived in Santa Cruz. This was in the late-90s. The house I stayed in was located in a wooded area called Pogonip. One of my housemates had a dog. One day in springtime I was playing with the dog. I came up behind him and straddled him like a horse. I leaned over and petted him on his head. I was wearing shorts.

36 hours later I was at work. I started feeling tingly on my legs. I kept joking to my coworkers that I was having an allergic reaction to my laundry detergent. That evening, I removed my clothes to discover strange red marks all over my legs, hands and arms. The next morning the rash started. It spread all over my thighs, calves, wrists, arms, nose, ears and neck. Some of you might not believe this but the rash lasted for over six weeks. It just wouldn't go away! It was hot and humid that spring in Santa Cruz. It seemed the humidity made it worse. It was so bad on my inner thighs I could barely walk. Just the vibration of taking steps was excruciating.

I eventually found a friend who told me to go in the ocean. I drove right to the beach after work and jumped in. The cold water didn't bother me--I was willing to try anything at that point. The rash went away in another three or four days.

The problem was, the house I lived in was covered in poison oak oil. The dog would get out and run around in the forest. Then he'd come inside and spread the oil around. None of my other housemates were allergic at all! I had a rash from March to September for the three years I lived there. I nearly went mad! I went through bottles and bottles of Technu. I'd carry around a freshly-laundered sheet so I could sit on the furniture. I'd wash my hands and arms constantly. In retrospect, I should have moved. But every spring I'd think--this year I'll be much more careful than last year and I won't get it.

I remember dealing with a rash all over my hands and wrists while on backpacking trips in the Sierra. The dry air did seem to help it clear up though.

I have to time my visits to friends in the Bay area from October to February. Otherwise I'll come back to Tahoe with a rash. My sensitivity to poison oak was a real catalyst in getting me to move up here.

I really belive the part in Markskor's article that says the more you're exposed to the oil, the more sensitive you get.

I'm so thankful this plant doesn't exist here in Tahoe!
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Postby Robert » Mon Jul 24, 2006 7:40 pm

Ooooo, what a pretty plant!

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Postby quentinc » Mon Jul 24, 2006 8:34 pm

It's even prettier with fall colors. A friend of mine swears that he once came upon a woman during a hike who was carrying armfuls of crimson and scarlet poison oak. He asked her what the hell she was doing and she explained she was gathering "fall foliage." He didn't say another word.
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Postby rightstar76 » Fri Jul 28, 2006 12:03 am

Most people aren't worried about poison oak. Last weekend I was hiking with my wife in Muir Woods as it was the only place in the Bay Area that was cool enough to go hiking. I was on the Ocean View trail above the main canyon and decided to ask some people coming from the opposite direction how bad the poison oak got since the poison oak was getting a little too close to the trail for comfort. They just laughed and said it was no big deal. Another person going the opposite way stopped right in the middle of the trail where some poison oak was growing. I pointed it out and she said she didn't know that it was poison oak and that she probably was immune to it since she'd never gotten it before. On the way back, my wife and I noticed some poison oak leaves on the trail that hadn't been there on the way up. We figured that it must have been caused by a family with a baby carriage on the trail. They had been coming down and the carriage was hitting everything in sight. It must have hit the poison oak. I felt sorry for the family and the baby. The trail is well signed but the park service and the state park aren't cutting the poison oak this year so things have gotten real bad. Honestly, I wouldn't have been that concerned about poison oak if I hadn't gotten it in June. The rash on my right elbow finally went away after about six weeks. It itched like crazy and I had to keep telling myself not to touch it. I've definitely learned to respect this plant.
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Postby giantbrookie » Fri Jul 28, 2006 12:11 pm

As a veteran geologist, who's logged many days of field work in the California Coast Ranges, I've had more than a few run-ins with poison oak, especially because I have frequently worked off trail.

Everyone hiking in the Coast Ranges, or in the lower altitudes of the Sierra where poison oak is also common, should thoroughly familiarize themselves with the appearance of poison oak in all seasons. As noted above the leaves start out green in the early season, then turn red in the fall before falling off. It is especially important to recognize the branch form of poison oak, so that you can avoid the stuff when there are no leaves on it to otherwise distinguish it. In its leafless form the stuff can be really nasty. Why? (in addition to the fact that it's harder to recognize) Because the bare branches tend to be somewhat brittle and their ends easily scratch the skin. When that stuff breaks your skin, watch out! I think the only thing that may be worse is the sap from poison oak roots. I've come in contact with the root sap in backhoe-excavated trenches and the effects were devastating.
Since my fishing (etc.) website is still down, you can be distracted by geology stuff at: http://www.fresnostate.edu/csm/ees/facu ... ayshi.html
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Postby rightstar76 » Sat Jul 29, 2006 10:34 am

I think the park service, state parks, etc. are partially to blame for not helping people recognize poison oak. At Muir Woods, there is a tiny flyer posted on one of the windows at the information booth. You really have to look for it and the print is very small. Earlier in the year when I was at Mt. Diablo SP, I asked a state park ranger if there were plans to put up signs educating the public on poison oak. He said there was no money to do this. He told me that last winter when it snowed people used poison oak branches to decorate snowmen.
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Postby dave54 » Sat Jul 29, 2006 6:18 pm

And yet more on the plant. For the real techno-nerd who wants to know about the ecology and physiological dynamics of the plant.

http://www.fs.fed.us/database/feis/plan ... v/all.html
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Postby fedak » Thu Aug 10, 2006 2:34 pm

Rob, Thats a good picture, decent hi-res photos of poison oak are hard to find online.

Never been particularity susceptible to the stuff myself (knock on wood) and heaven knows I've crawled through enough of it.
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