Putting up some symbolism

The Pine Tree Flag and the Palmetto Guard  Flag are both classic American standards with loads of attitude.

The pine tree had long been a New England symbol being depicted on the Flag of New England flown by colonial merchant ships dating back to 1686. The pine tree appeared even earlier on coinage produced by the Massachusetts Bay colony (the "Pine Tree Shilling") from 1652 to 1682, a period of relative independence for New England during the English Commonwealth.  Leading up to the Revolutionary War the pine tree became a symbol of Colonial ire and resistance as well as multi-tribal support of Independence.

The white pine found in New England, specifically the eastern white pine (Pinus strobus) with heights exceeding 150 feet, was highly desirable for constructing masts in shipbuilding. Twenty years after arrival in the new world, the Pilgrims harvested and exported these pines as far as Madagascar. Due to lack of supply of suitable lumber on the island, England reserved 24 inch (61 cm) diameter trees under the Mast Preservation Clause in the Massachusetts Charter in 1691. The trees were identified by a Surveyor of the King’s Woods (a position of preferment) who would, in turn, appoint deputies to survey and place the broad arrow symbol on the tree from three hatchet slashings denoting property of the Crown. 

The broad arrow statutes were not immediately enforced, due to England having access to other sources of timber in the Baltic. However, when this source diminished, additional broad arrow policies acts were passed and enforcement increased in North America.

The statutes required colonists prior to harvesting trees from their property to have a King's Surveyor mark the larger diameter trees with the broad arrow and then purchase a royal license to harvest the trees not marked with the broad arrow. The colonists resented the strictures on the timber used for their needs and livelihoods. Prohibitions were disregarded and they practiced "Swamp Law", where the pines were harvested according to their needs regardless of statutes.

In New Hampshire enforcement led to the Pine Tree Riot in 1772, where a statute had been in effect since 1722 protecting 12-inch diameter trees. After being fined and refusing to pay for possessing trees marked with the broad arrow, a New Hampshire mill owner leading other mill owners and townsmen assaulted the Sheriff and his Deputy sent to arrest him by giving him one lash with a tree switch for every tree which the mill owners were fined, cutting the ears, manes, and tails off their horses, and forced them out of town through a jeering crowd. This was one of the first acts of forceful protest against British policies. It occurred almost two years prior to the more well-known Boston Tea Party protest and three years before open hostilities began at the Battles of Lexington and Concord.

Months prior to Colonel Reed's suggestion for using the pine, the pine was used on the flag that the Colonists flew at the Battle of Bunker Hill in June 1775. The historically accepted flag has a red field with the green pine tree in the upper left corner as depicted in John Trumbull's  The Death of General Warren at the Battle of Bunker's Hill, June 17, 1775 painting. Provided Colonel Reed was aware of the Bunker Hill flag, there was a precedent to incorporate the pine in another Colonial martial flag.

Given the pine tree's significance to the Colonists and since the flag was to fly over Colonial warships, the pine offered an appropriate and ironic symbol due to it flying atop the very structure the British had sought to harvest the white pine for.

Well into the 20th century, the pine tree was a symbol of New England. The state of Maine adopted the 1901 Maine Flag which prominently featured a pine tree alongside a blue star.

The phrase "An Appeal to Heaven" is a particular expression of the right of revolution used by British philosopher John Locke in Second Treatise on Civil Government which was published in 1690 as part of Two Treatises of Government refuting the theory of the divine right of kings.  Basically, the only higher authority recognized by the king was God, and an appeal to heaven was an in your face appeal over his head to the ultimate authority for redress of unjust treatment by the English sovereign.

Locke's works were well-known and frequently quoted by colonial leaders, being the most quoted authority on the government in the 1760-1776 period prior to American independence.

As to the Palmetto Flag, it Began as the Moultrie, or Liberty Flag, and was designed in 1775 by Colonel William Moultrie, to prepare for war with Great Britain. 

It was flown by his troops in the successful defense of Sullivan's Island against the British fleet in June 1776. 

Fighting back stridently during a ten-hour bombardment and siege, Moultrie's forces (primarily the 2nd South Carolina Regiment) eventually led the British to withdraw entirely, saving Charleston.  It is said that the walls of the fort were lined with palmetto logs, and being somewhat spongy, the British cannonballs simply were absorbed or bounced off, rendering the cannonade far less lethal.

During the battle, the flag was actually shot away, but Sergeant William Jasper ran out in the open and hoisted it again, rallying the troops until a new stand could be provided. The story of this dramatic event, along with the pivotal role of the battle itself, earned the flag a place in the hearts of the people of South Carolina, as well as cementing it as a symbol of liberty in the South, and the new confederacy in general.

It therefore became the standard of the South Carolina militia, and when the war officially ended with the liberation of Charleston, on December 14, 1782, it was presented by General Nathanael Greene's "Southern Continental Militia Army," as the first American flag to be displayed in the South.  Later versions added the palmetto tree, in honor of the spongy old palmetto logs that unexpectedly foiled the British, and it was the first flag raised by the South Carolina militia over Fort Sumter in Charleston Harbor after eviction of the federal troops there at the beginning of the Civil War, and is still on the modern flag of the state of South Carolina.

So we have American battle flags from both the north and south, warning enemies not to tread on we Americans, and flying together in harmony and brotherhood, as it should be.