It was revelatory to read that George Washington left his mother's grave unmarked, according to Myron Magnate's accout:
...from every indication, his mother...was unloving and exploitative at best, mentally unbalanced at worst, a potentially soul-
destroying burden for a fatherless boy - or a spur to assert his worth all the more forcefully...
Washington's later dealings with her, from which we have to infer the past, display frostily correct dutifulness on his part, belittling, ungrateful complaint on hers. Having twice tried to thwart his military career, she dismissed his martial exploits by saying, "Ah, Goerge had better have stayed at home and cultivated his farm." In 1772, after letting her have Ferry Farm rent-free for three decades, he bought her a pretty house in Fredericksburg, lent her money she never repaid, and gave her an allowance. Nevertheless, in 1781, as the Revolutionary War was ending, she asked the Virginia Assembly for a pension, saying she was "in great want," a move that Assembly speaker Benjamin Harrison knew would so mortify Washington that he sent the general a warning letter, so he could quash the scheme. After years of such antics, Washington wrote to remind her how generously he had treated her, to assure her that "whilst I have a shilling left you shall have part, if it is wanted, whatever my own distresses may be, " and to reproach her for causing him to be "viewed as a delinquent, & considered perhaps by the world as [an] unjust and undutiful Son." When told that Fredericksburg had planned a ball to honor Washington and his French allies for their victory at Yorktown and that "His Excellency" had agreed to come, Mrs. Washington sneered "Hs Excellency! What nonsense!" After his death in 1789, her son the president left her grave unmarked.
p. 95
http://www.librarypoint.org/mary_ball_washington
Washington's mpther's grave