constructed and planted south of the house. To the west of Arlington House, tall grass and low native plants led down a slope into a natural area of close-growing trees the Custises called "the Grove." About west of the flower garden, "the Grove" contained tall elm and oak trees which formed a canopy. An informal flower garden was planted beneath the trees and maintained by the Custis daughters before 1853. Upon George Washington Parke Custis's death in 1857, he left Arlington Estate to Mary Anna Randolph Custis Lee for her lifetime when it would then go to her eldest son, George Washington Custis Lee. The estate needed much repair and reorganization, and Robert E. Lee, as executor of Custis's will, took a three-year leave of absence from the Army to begin the necessary agricultural and financial improvements. Civil War In April 1861, Virginia seceded from the United States. Though offered command of the U.S. Army, Robert E. Lee resigned his commission on April 20, 1861 and joined the Confederate States Army. With Arlington House on high ground overlooking the capital, the government of the United States knew it must occupy the mansion or be left in an untenable military position. Although unwilling to leave Arlington House, Mary Custis Lee believed her estate would soon be occupied by federal soldiers and left to stay with relatives on May 14, having been warned by her young cousin William Orton Williams, then serving as aide to General Winfield Scott. Union Army troops seized and occupied Arlington without opposition on May 24. In June 1862, the 37th United States Congress enacted legislation that imposed a property tax on all land in "insurrectionary" areas of the United States. The 1863 amendments to the statute required these taxes to be paid in person. But Mary Lee, afflicted with severe rheumatoid arthritis and behind Confederate lines, could not pay the tax in person. The Arlington estate was seized for nonpayment of taxes. It was auctioned off on January 11, 1864, and the U.S. government won the property for $26,800 ($ today). During the war, Union Army troops cut down many of the trees on the Arlington estate, especially those to the north and east of Arlington House in and near Fort Whipple (north of the house) and Arlington Springs (near the Potomac River). However, a number of large trees remained, particularly those in a forested area (now