The Note about the Bundle of Roots is a story item found in the area northwest of the Road to Home, in a wardrobe right next to the Radio Tower Bunker's exit. Note that what is called "wardrobe" in-game looks more like a pile of sacks.
The note describes someones findings from researching the tree roots in Darkwood:
"The roots have made it impossible to dig further. Specialist tools will be needed if we are to go deeper.
Observation:
The roots of individual trees intertwine to create bundles (braids) with the thickness of 120 centimeters. The ones we analyzed always grow towards the north-east. Taking into account the results from the dig sites from other regions, we can assume that the bundles come together in sector 0. We have accumulated about 5 litres of the substance that flows through the roots. As expected, it has lost its shapeshifting abilities after being disconnected from the root (from the stream, to be exact)."