Here's why:

* Earth's Formation: 4.6 billion years ago is the estimated age of Earth's formation. At this time, the planet was a molten ball of rock and lacked the necessary conditions for life.

* Early Life: The earliest evidence of life on Earth is around 3.5 billion years ago, and it was likely single-celled organisms, not plants.

* Plant Evolution: The evolution of plants took millions of years, with the first land plants appearing around 470 million years ago.

So, while Earth was forming 4.6 billion years ago, there was no life, let alone complex plants like we know them today.