c. 4,500,000,000 B.C.A race of advanced beings known as the Forest Lords and their master, Sila, seed planets throughout the universe with the potential for life (green, blue, red and violet). On some worlds, life never takes hold, but on three planets in the Sol System (Earth, Jupiter and a fifth planet, now perished), life thrives. On Earth, the plant kingdom form a conscious realm called the Green, while on the fifth planet, evolution bases itself on fungi and molds.
Swamp Thing (Series 2) #104: “The Quest for the Elementals I—Matango”
NOTE: Issue #168 says the Parliament of Trees first attained sentience 4.5 billion years ago. Since we know that the Parliament was sentient from its very inception (the first member, Yggdrasil, was born sentient), we can place these events in that era. It should be noted that this negates scientific evidence that land plants appeared on Earth 435 million years ago; however, since a specific figure is given, that supercedes scientific theory.
In response to the ravages of nature, Earth calls forth an elemental, an Erl-King, as its spirit protector.
Swamp Thing (Series 2) #47: “An American Gothic—The Parliament of Trees”
Thrown back in time by the Claw of Aelkhünd, an earth elemental from the future known as Swamp Thing (once the scientist Alec Holland) becomes this first spirit protector. As the Parliament of Trees does not yet exist to counsel him, he grows a vast brain to consider his options in creating them. He realizes he must guide Earth's infant biosphere, for his destiny is to spawn his own Erl-King lineage.
Swamp Thing (Series 2) #89: “Founding Fathers”
The Earth spirit She-Who-is-the-World, desiring shepherds to watch over her Earthen form, permits the creation of the Erl-King Yggdrasil, knowing it will lead to the formation of the Parliament of Trees.
Black Orchid #9: “The Murmuring of Mists, the Whispering of Flowers”
NOTE: In Norse mythology, Yggdrasil ("The Terrible One's Horse", also called “the World Tree”) is a giant ash tree that links and shelters all the worlds.
Using a seed a Neanderthal named Rheelai will give him in 40,000 B.C., Alec forms Yggdrasil in a spot that will some day be called the Garden of Eden. This elemental, shaped like a DNA strand, takes its name from Alec's knowledge of Norse mythology. Yggdrasil is the first elemental in a long line that will eventually be known as the Parliament of Trees.
Swamp Thing (Series 2) #89: “Founding Fathers”
In spawning the Parliament of Trees, Alec passes down his memories to Yggdrasil, who in turn will pass them down to the other Founders who follow him.
Swamp Thing (Series 2) #104: “The Quest for the Elementals I—Matango”
After creating Yggdrasil, Alec realizes why the amber Claw of Aelkhünd has been tossing him ever backward through time: it is a gateway to the Tree of Life, and his key to going home. Alas, a volcanic eruption disturbs Alec's meditations, threatening to destroy him before he can make the leap.
Swamp Thing (Series 2) #89: “Founding Fathers”
The volcano's lava dissolves Alec’s body, trapping him in amber crystal as it hardens. Unable to escape, he spends the next half-billion years encased in crystal, fading in and out of consciousness as he relives the stops of his journey back through space-time, but this time in proper chronological order: first billions of years in the past, then a Neanderthal village in 40,000 B.C., and on to Jerusalem in 33 A.D., sixth century Camelot, 1780 and 1872 in the Old West, World Wars I and II, and finally 1989, when John Constantine will free him from his crystal prison.
Swamp Thing (Series 2) #90: “Journeys”