The speaker watches silver birches and dark pines growing out of a dense, shadowy forest floor. Around them are stunted shrubs, creeping vines, damp air, and even eerie glows and poisonous fungi. Yet the trees keep reaching upward, lifting their heads into the open breeze, the sky, clouds, and sun. The scene has a quiet, slightly mysterious mood at first, but it becomes hopeful as the trees escape the darkness below.
The final two lines turn the trees into a gentle instruction for the soul. Just as the forest trees strive upward from shadow and decay into the light, the speaker encourages the soul to rise from earthly darkness, struggle, or doubt toward something brighter and freer. It feels like a quiet call to keep reaching beyond what weighs us down.