Strange Things I’ve Seen – Mysterious Blue Pine Sap on Carstairs Trail‏

Update – June 18, 2018 – RESOLVED !  Please see KHL’s comment below for an explanation to this phenomenon. Many thanks KHL.


Update – May 28, 2018 – The University of Guelph has no idea either.

Update – April 25, 2018 – I heard from a Provincial government ministry today. They explained why a blue spruce tree is blue, and suggested maybe it was by the same process. However, I’m trying to figure out why trees are oozing puddles of bright blue sap/resin/whatever, from under their bark, not why the needles of one species of pine appear kinda blue. I’ll just have to keep asking I suppose. 

Update – April 21, 2018 – OK, now we have reports of the same oddity from, British Columbia, Austria, and Colorado. Last week I attended a Spring gardening show and questioned a number of professional arborists. None could shed any light on the subject, as if they’d never even heard of such a thing. But they gave me some names and contacts to try. I’ll chase up those leads and post another update when I hear back.

Update – April 1 2018 – Not sure if this is a “Nature April Fool” but, over the last few weeks, I’ve seen alot of trees on numerous other trails, exhibiting this blue sap behaviour. I’ve been wandering the bush for alot of years but don’t recall seeing this “blue bleeding” thing until I saw it at Carstairs.

UPDATE – June 20 2016 – Since the addition of interpretive signage on this trail, we now know these trees are European Larches. Still don’t know why they “bleed” blue sap though.


Back in April the wife and I were re-visiting the Carstairs trail because Peter’s Woods wasn’t open for the season yet. As we rounded the first bend in the trail, the wife spotted something extremely blue running down the side of a tamarack tree (I think).

Everyone’s seen pine sap with a pale bluish hue to it, but this was far beyond that. The following pics have not been altered, in fact the color intensity captured by the camera was less than appeared to the eye at the time, due to the angle of the sunlight.





Of course, I Googled for an explanation. The best I got was a sap-sucking fungus carried into pine trees by a beetle with a decidedly far Western name, which stains freshcut wood with a pale blue tinge. But this was a seriously bright blue ooze that had even puddled on the ground at the base of the trunk. So, I printed out those pics, and took them to the Ganaraska Region Conservation Authority.

I started getting excited when no one could figure out what it was. Excited and  concerned because as much as I love a poser, I hoped we hadn’t found something problematic. The GRCA’s Forester was attending an off-site meeting, so I left the pics there with my Home phone number. By the time I got Home the wife, met me at the door with the news that the GRCA Forester had no idea what it was either.

So, since the GRCA couldn’t explain it, I contacted the ROM (always very helpful in the past as well). That was a month ago, and after a coupla e-mails back and forth, no one has come up with an explanation. So, I guess this is a mystery to be pondered at length.

If anyone reading this has similar observations or can offer an explanation, please let me know. Thanks.




  1. I have a pine tree in my backyard which all the sudden got covered in a beautiful blue sap and I can’t find any info on the reason it’s this color. I’m not sure it’s about the species of tree as I am in Austria.


    1. Hello Edo,
      Thanks for your input. So this happens in Europe too ? I first thought it just affects larches because they are not indigenous to Canada. But just last week, I saw a definite pine bleeding deep blue. I have no idea what causes it, but none of the trees I see doing this seem to be in distress. They all appear to be quite healthy. The only thing that concerns me is that no one can tell me what it is. I hope it’s nothing serious. If I ever get an answer, I’ll post an update. Thanks again Edo. Bye for now,


  2. It is happening here in southern British Columbia, Canada as well. Very puzzling.


    1. Thanks for your input Judy. While researching this phenomenon I read about a fungus carried by a beetle in the BC forests which will cause blue staining of the wood. Just the wood though, not actually bright blue sap oozing from the trees. So now it’s showing up in BC, Ontario, and according to Edo (in Austria), it’s there too. I’m gonna have to keep pushing my question up the ladder.

      Thanks again,


  3. Anonymous · · Reply

    I live in Colorado and the pine’s sap turned blue in my front yard. I don’t know if there’s any correlation but I noticed it after some really strong wind…


    1. Thanks for your info. Last week, I was asking an arborist about it, when he smiled and said “Maybe you’ve discovered something they’ll name after you”. I’d prefer not to have ANYTHING named after me, if you know what I mean.
      Thanks again,


  4. Tamara · · Reply

    Did you ever get a real answer? Saw the same blue sap today in Glacier National Park and am super curious.


    1. Not really Tamara. Any suggestions I’ve received don’t even come close to making any sense. Most of those I’ve asked, claim to have seen it themselves, but can only guess at what it is. All I know thus far, is that it seems to only affect conifers, and no one has done any research on it (yet). Now that I say that … I haven’t tried contacting any Universities to see if a student somewhere might be doing a thesis on it. Thanks for prompting the idea Tamara. I’ll get on that.



  5. I came across your page while trying to ID the blue draining liquid on a tree I saw last weekend in the Santa Cruz Mountains in California. I saw a number of similar photos, with several saying that the underlying problem is slime flux. This one, from the U of Idaho seems to be the most succinct (, but if you do a Google image search with keywords such as sap, tree, blue you should find more examples. I also searched using the words slime, flux, tree and found more info. Blue still seems to be a less-common color and may be due to the particular type of bacteria that grown in the flux.


    1. Thank you very much KHL,
      That’s exactly what I saw and have been trying to explain from the start! This issue is resolved.


  6. Glad to have gotten it figured out for both of us!


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