<p>Meh. I've always thought earth as the least spiritual element, since it's so... <i>earthy</i>. Remember how Korra had so much ease with earth- and firebending? That's because she was, at the time, more aggressive and headstrong. That's why she had so much trouble with airbending, obviously the <i>most</i> spritual element. That's also why Aang, a very spiritual airbender, had so much trouble with earthbending. I don't think spirituality has much to do with sensing vibrations in vines, I think instead they may assist by augmenting vibrations or something.
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