Disclaimer: I don't own any content of the ASOIAF universe, they belong to George RR Martin. No Money is made of it. Other works inspired me so some similarities with others exist.
Authors Note
No Beta, Reviews Welcome though please keep in mind this is my first story.
House Gardener claims its descent from Garth Greenhand, the High King of the First Men via his eldest son Garth the Gardener, First King of the Reach. An enviable heritage to be sure, one which made it fitting then that House Gardener would be the ones to unite the Reach under their rule.
However, while House Gardener was famous for their legendary founder they were even more famed for their position as Kings of the Reach. From their petty kingdom ruling a stretch of the river Mander, they soon grew on the back of their military strength and shrewd diplomacy. Until they came to rule the Mander proper becoming one of the most powerful houses in the Reach, controlling the mighty river and the lands, Westeros's most fertile, surrounding it, giving truth to their words "We make the Gardens Bloom".
However, House Gardener's ascent would be halted by the coming of the Ironborn. During this Age murders, reavers and rapist would attack at any moment, their longships coming to shore before any could even notice them on the horizon. Like many other of the Houses at the time the Gardener's paid tribute to the Krakens, not that this would stop the pillaging. After Generations of terror, the Gardener Kings decided to fight back and to overthrow their oppressors. Under their leadership, the Kings and lords of the Reach swept the squids back into the sea, with Garth Goldenhand taking the shield islands from the Ironborn and using it to defend the Mander and the Reach.
Over time the Gardener's would bring more and more houses under their rule, using diplomacy and marriage instead of war, a practise which allowed them to continue to hold on to their lands and titles despite the Andal Invasion. In time the Gardener's would come to rule the Land we all know as the reach today. That is not to say they were invincible or all knowing, after all the reign of Garth Greybeard showed that the Gardeners could lose control of their lands just as any other lord, But there was no doubt among the people of Westeros however that the Might and Wealth of Highgarden could be matched by few if any.
As such when Aegon Targaryen sent word of his claim to westeros, the Lord and princes of the Reach cared little for his supposed strength and instead bickered on who would get what part of the dragons once they slew these exotic beasts, so confident in their own strength. None took heed of the past, none took heed of the writings of maesters, traders and adventurers from across the narrow sea telling of the might of the great Valyrian empire, built by the Dragon lords, none took heed of common wisdom telling that charging at an army even a smaller army on an open field when the other side had fire breathing dragons would have them killed, even the burning of harrenhal was not enough. No one took heed except one. Prince Garth Gardener third son of King Mern IX, also called the Maester Prince showed none of the confidence of his kin and instead implored the king and House Gardener to use diplomacy once again instead of force, pointing to Harrenhal and House Hightower's surrender as evidence of Aegon strength.
But his pleas were dismissed by the foolish old king, who had tales of glory whispered in his year by both his bannermen and even the "loyal" stewards of house Tyrell, who saw this as an opportunity to increase their own power and standing in the Reach. As such, the king decreed, a fortnight before they were to march to meet the forces of King Loren of the Rock, Prince Garth and his three sons Willas, Lyonel and Mern were to remain behind at Highgarden.
This punishment was in the end known to westeros as the Gardeners Salvation, which along with the Great Betrayal and Mern's Folly would change the course of House Gardener and the reach forever.