I have a very large pine tree in my back yard, and I believe that the oil somehow discolors the cream paint on my painted wooden siding. The discoloration is a grey blue color.

If I'm correct, then I would welcome a solution.

Thanks. I am located near Toronto in Canada. The tree is about twice the height of the house, and its lower limbs extend very close to the house. The tree is more or less south of the house. The side of the house in question sees the sun in the morning. Last year I tried to climb the lower portion of the tree, and failed for it was covered in sticky sap.Follows is a picture of the contamination.


  • Can you take and post a photo? You won't be able to add it directly to the post until you get 10 rep, but post the link and someone else can add it for you. Also a description of where the tree is in relation to the house (distance, compass direction, etc.) would be useful. And if the house is heavily overshadowed by the tree, the staining could be mildew. – Niall C. Sep 23 '12 at 1:01
  • Pine Tree sap contains terpene, the major constituent of turpentine, a commonly used oil based paint thinner. To a lesser extent, there are terpene alchohols that probably aren't good for stuff they land on. I've had pine pitch discolor car paint. – Fiasco Labs Sep 23 '12 at 1:48
  • It may be a case where the sap residue is allowing other things like pollen, plant spores or mold spores to stick to the paint. – mikes Sep 24 '12 at 12:50

I bet what you are seeing is mildew growing on dust on the wall. The dust can be formed of the white blush on the needles of the pine, or it may jsut be taht the pine protects the house from wind, so dust collects there.

I would expect dripping to be, well, more drip like -- more blobby.

If it's mildew, it should come off with a weak bleach solution. (1 cup per gallon of water, along with a table spoon of TSP per gallon. You may have to wash it once with the bleach, wait a day, then wash with the TSP.

it's actually sap, it is essentially oil based. Try winter windshield washer fluid, about 40% alchohol, or diesel fuel, and a scotchbrite nylon scrubby. DON'T use gasoline.

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