Final answer:
Plants started colonizing the land around 500 million years ago, with the oldest fossils of land plants dating back about 470 million years.
Step-by-step explanation:
Plants began colonizing the land approximately 500 million years ago. The oldest fossils of terrestrial plants have been dated back to about 470 million years, suggesting they may have begun colonizing the land even earlier, around 700 million years ago. These early land plants were likely similar to modern liverworts. It is important to note that photosynthesis, the process fundamental to plant life, began significantly earlier, between 3.5 and 2.5 billion years ago. However, the presence of multicellular forms of plant life on land followed much later. Fossils provide evidence that by 250 million years ago, fungi, often associated with early plant life, may have been dominant life forms on Earth.