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The weather stick, old timey humidity meter — How does it work?

maine_tyler | Posted in General Questions on

I recently finished cutting the corridor of a hiking trail here in Maine, and we made sure to cut in a good bit of head room using a pole saw. This was during late July and early August when humidity was high. It’s been a wet summer.

We finally got some drier weather here last week. I noticed many standing puddles finally dry. I also noticed that small dead branches were now brushing my head on the trail. What gives?

Then I remembered being at a friends camp where they had a ‘weather stick’ on their porch. Apparently it predicted the weather. More likely it reacts to it.

Here is a link discussing the weather stick:

So what are your theories as to the mechanism at play here? My initial hypothesis was that the reaction wood was responding differently to the relative humidity. The above article claims it also works for the (straight) main stem of balsam saplings though (but which way does it bend?). The article also wonders if it’s dewpoint and not RH. I wonder if it might be vapor pressure deficit…

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  1. Expert Member
    DCcontrarian | | #1

    It's the nature of that species -- the branches rise when they're wet and fall when they're dry. It's due to the cellular structure so it continues even when the tree is dead.

  2. gusfhb | | #2

    We got so much rain they probably grew a bit longer[heavier]
    Just cut the grass, never gut the grass in late August.....
    My hemlocks curl down hard when the branches are dry/dead

  3. Expert Member
    Michael Maines | | #3

    I walk in my woods daily and have noticed that branches, especially on hemlocks, will droop when dry and perk up when damp. I'm guessing it's a built-in feature involving the reaction wood on the top of the branch; the reaction wood is probably like scar tissue and can't absorb as much water, but the bottom of the branch absorbs water and swells, lifting the branch, or dries and makes the branch droop, while the top of the branch remains a consistent size.

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