I'm looking at the middle of a 3" tree root, that's intruded under a slab and along plumbing. How can I determine "which direction to the tree"?

I've cut a section out of this root. One end is damp, the other is literally dripping water (and has dripped for days). Given the position of the root, either way could be the tree trunk. Digging to find out which is not practical.

Is there any such thing as a tracer die that can be injected, then found on the tree trunk?

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  • What tree is it? What's the weather like at present? Jan 31, 2018 at 23:58

1 Answer 1


The force that drives water from the soil to the tree top is hydrostatic pressure caused by evaporation of water from the leaves. So, when you sever a root, you remove that hydrostatic pressure from one side. There is no longer a significant force to draw water from the fine roots back to the leaves so the side that leaks the lesser amount of fluid is the remote side of the cut.

The tree is still able to send carbohydrates etc to the roots and so the side that is gushing fluid is the tree side of the cut.

  • Cool. Could you state any authority for that answer (e.g. "xxx garden manual" or "my training as a...."? there should also be some capillary pressure from the root side. The answer in this case is consequential: a tree's life hangs in the balance.
    – Bryce
    Jan 31, 2018 at 20:19
  • I'm not sure my answer is correct now. Jan 31, 2018 at 23:57

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