A profound spiritual lesson from tree symbolism comes from the roots. They serve as anchors, gripping tightly into the Mother (Earth). They form a symbiotic union with the earth, drawing from her various nutrients and water. Tree roots can span for miraculous lengths - like branches - ever reaching out for more. This is metaphoric of our own inner root systems of beliefs and spirituality. We must dig deep, and be firmly rooted in a structured system of beneficent beliefs. It's the only way we are insured upward mobility.
A vital observation about roots is they are unseen. They remain (mostly) underground. In much the same way, our spiritual progress will be hidden from view to the common eye. Our growth and power occurs beneath superficial layers. Moreover, our belief systems are much like root systems of a tree - they are sacred, tacit and they anchor us in our lives.