hemlock, (kokuji)
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栂 is a Japanese kokuji for the hemlock tree, specifically the species Tsuga. Its meaning is tied directly to that tree.
southern Japanese hemlock (species of conifer native to Japan, Tsuga sieboldii)
mountain heath (Phyllodoce nipponica)
Japanese Douglas fir (Pseudotsuga japonica)
northern Japanese hemlock (Tsuga diversifolia); hemlock spruce
western hemlock (Tsuga heterophylla)
Aleutian mountainheath (Phyllodoce aleutica)
栂 is a Japanese kokuji created by combining 木 (tree) with 母 (mother), possibly chosen for its sound contribution (つが/とが) to represent the hemlock tree. The exact reasoning behind the component choice is uncertain.
A tree (木) that is like a mother (母) to the forest, providing shelter and shade: the hemlock tree.
For つが, imagine a hemlock tree with two (つ) moth (が) cocoons hanging from its branches: つが.