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For a very long time now, I've believed and taught that burning Rhododendron or Mountain Laurel in a campfire will make you sick because of the toxins in these plants becoming airborne then inhaled around the fire. Many people I know that I trust also believe the same thing, but is this really true? My own research hasn't found anything definitive; most say yes, some say no. The plants most certainly have toxins in them, but most information pertains to ingestion of the toxins, not burning them.

This question is similar, but not the same. It's only answer also provides no references.

This stuff is everywhere in my region and it would be so much easier and quicker to gather firewood if it proves to be possible to burn the dead wood of these plants, and related species, without ill effect.

In addition, I'm really looking for more definitive information than anecdotal evidence. That type of evidence is certainly useful, but I really think this needs more than something that says, "I'm still here" type of thing.

  • We try to avoid burning Laurel leaves(not mountain just the garden stuff you get in the UK), but we burn the wood regularly mixed in with other garden / household woods. – Aravona Nov 11 '14 at 8:16
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Poisonous plants are typically more dangerous when you burn them, at least that's true with plants that have oily toxins (poison ivy/oak). Toxins in plants aren't necessarily vaporized when burned. Smoke is a particulate, not a vapour. If you are burning something toxic, the toxins can potentially be carried by particles of smoke and be inhaled which is far more dangerous than being consumed in some cases. Even dead plants can still be toxic.

The toxin in Rhododendron and Mountain Lily is Grayanotoxin. Every material safety data sheet I've looked at says that Grayanotoxin is fatal if inhaled. But that's for pure manufactured Grayanotoxin II.

That being said, this guy thinks Rhododendron makes great firewood:

"Another property of rhododendron is that it makes excellent firewood – even when it is green. It is a fast-growing hardwood with a very high calorific content, and the stems of larger plants are so thick that they can easily be sawn up into logs which are perfect for either an open fire or a wood burning stove. I have taken rhododendron logs home to burn in my woodburner during the winter, but a particularly good use for the rhododendron firewood is on-site, where I need to keep warm during the winter when I am there working. Burning rhododendron means that I can generate firewood as I am clearing the rhododendron from the woodland, meaning that I don’t have to have a big stack of it seasoning and I don’t have to cut down broadleafed trees and season them for use as firewood on-site, I can leave them standing and growing. So rhododendron has become my staple firewood, leaving the trees for better purposes."

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And the Scottish government recommends burning Rhododendron to control its spread as an invasive species, so it would appear that it is at least less toxic than poison ivy or poison oak when burned.

They say that one of the first indications of Rhododendron poisoning is salivation, I suppose you could have a campfire in your yard and see if the smoke makes you drool... But I think the fact that the guy in the Blog is praising Rhododendron as fire wood, that he burns indoors and is still alive and blogging means that it's probably ok to burn for heat outdoors. I probably wouldn't inhale the smoke though... or roast hotdogs over a grayanotoxin fire...


Edit:

Over 1000 species of rhododendrons/azaleas exist. All parts of the plant are considered poisonous, and as little as ingestion of 0.2% of an individual’s body weight can result in poisoning. When ingested, clinical signs include gastrointestinal signs (e.g., drooling, vomiting, diarrhea, abdominal pain, inappetance), cardiovascular (e.g., abnormal heart rate, heart arrhythmias, weakness, hypotension), and central nervous system signs (e.g., depression, tremors, transient blindness, seizures, coma, etc.). The overall prognosis is fair with treatment.

When burned the gryanotoxin is destroyed at temperatures of 150 degrees Celsius and above, and no evidence of toxicity has been found in the smoke or coals of the rhododendron plant. It is a hard long-burning wood and can be used safely.

However, inhalation of any smoke from any fire can have harmful health effects and should generally be avoided.

  • @manoftheson - The measure is three... three toxicity units... (Brian Regan anyone?) What kind of measure would be useful to you? Do you want to know how many parts per per million will kill you? How many puffs until you get a buzz? I could probably find out how much is in the wood, how it reacts to fire and how much is actually released into the air, but how much of that would you find useful? What exactly do you want to know? – ShemSeger Nov 18 '14 at 4:22
  • @manoftheson - It appears that Grayanotoxin is destroyed in high heat, so there are no toxins in the smoke of burning Rhododendron. See my edited answer. – ShemSeger Nov 18 '14 at 7:22
  • I definitely laughed there. And fair enough, I wanted more specificity but wasn't specific enough even still. And where did you find out that it's destroyed by heat? – manoftheson Nov 18 '14 at 7:43
  • @manoftheson - It wasn't from anything solidly sourced, I think I am curious enough now though that I'm going to keep looking into it until I find something reliable. I did find some sources that said boiling the plant neutralized the toxin, but that conflicted with the higher burning temperature... – ShemSeger Nov 18 '14 at 19:16
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    Yep, I volunteer with a Scottish tree charity, and we slash and burn Rhododendron with a passion. We're usually out in the field around 6 hours at a time and nobody has ever come down with any issues exclusive to burning the Rhododendron wood! – Korthalion Sep 22 '17 at 9:58
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At least for some species, Rhododendron wood is not especially toxic when burned. I've seen (and used) many species of Rhododendron in the Chinese Himalaya as firewood, in both outdoor and drafty indoor conditions. This included seasoned and unseasoned wood, and large enough quantities of smoke that my Rite-in-The-Rain notebooks still smell like bacon.


Long tangent on Rhododendron Toxicity

While this doesn't directly address the question of burning Rhododendron wood, the whole idea that Rhododendron smoke might be poisonous springs from the idea that it is a very poisonous plant to ingest. And, while I'm not encouraging anyone to eat large quantities of Rhododendron, I suspect that the often-repeated stories about its toxicity are overblown:

Tales of poisonous Rhododendron honey go back literally thousands of years (and were even repeated in the 2009 Sherlock Holmes movie!), but don't apply to all species / methods: Rhododendron honey is common in the Himalayas, and made in Europe as well (it's tasty!). It's used in Asia and Europe as a medicine. Most of the modern cases are of people becoming sick from using medicinal-grade Rhododendron honey.

There's also evidence for species differences and processing effects (drying reduces grayanotoxin) on the toxicity of other parts of rhododendron, both from chemical studies, and again from my experience in the Himalaya, where flowers of some Rhododendron species are eaten and others considered poisonous, and leaves of some species used as animal forage and others for animal medicine. American Rhododendron vegetation is more famous for poisoning livestock, but this also varies between goats and sheep who show more ill effects, and deer with fewer. The toxicity seems to be even less in humans, and the cases of poisoning are in fact very rare.

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    I once had two young goats escape and consume a small rhododendron bush between them. One died and one survived. Small quantities may be unpleasant, but it's possible to make a complete recovery. No idea whether inhalation would have similar results. – Toby Speight Sep 22 '17 at 10:26

protected by Reinstate Monica Mar 7 '18 at 15:57

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