What did trees evolve from

The vascular plant emerged around 400 million years ago and started Earth's forest-building process during the Silurian geologic period. Although not yet a "true" tree, this new member of the terrestrial plant kingdom became the perfect evolutionary link (and the largest plant species) with developing tree parts and considered the first proto-tree. Vascular plants developed the ability to grow large and tall with massive weight needed for the support of a vascular internal plumbing system.

Answer: Well the first plants to invade the earth did so about like ... 400 million years ago. Only after vascular tissue and after that roots evolved could trees evolve. The earliest trees were tree ferns.