At Poplar Forest, Jefferson integrated the design of the house and ornamental landscape. Today, however, few of Jefferson's landscape features remain. These include the sunken lawn behind the house, the two mounds flanking the house, the poplar trees north of the house, and portions of the road system. In Jefferson's time, ornamental plantings would have been associated with these features and other parts of the lawn immediately surrounding the house.
Since 1989, archaeologists have explored the landscape using a variety of methods. What they have found is an elaborate scheme, with major elements that changed over time as Jefferson tinkered with his plan.
As with other types of archaeology, landscape archaeology involves researching documentary evidence. Archaeologists gained an overall understanding of the landscape design by reading letters and memos that Jefferson wrote.
For instance, in December 1812 Jefferson directed that on the sunken lawn: "Plant on each bank, right & left, on the S. side of the house, a row of lilacs, Althaeas, Gelder roses, Roses, clianthus."
Written evidence leads to more questions. Were specified plants actually planted, and if so, where exactly? How did Jefferson shape and use the landscape?
Differences in soil offer clues to past landscape activities. The trained eye can detect planting holes, for instance, by soil that is darker and less compact than the surrounding dirt and patterned as circles or squares. Often they contain charcoal, lime, or other substances added to the soil as fertilizer.
Post holes of long-gone fences are evident by cores of soil darkened by the remains of the post. When excavated, the holes are fairly deep squares or circles, regularly spaced at intervals usually averaging about 10 feet.
Road traces can often be seen even before excavations as flat, linear depressions in the ground. When uncovered, they are often marked by compacted soil mixed with cobblestones, bricks, or gravel.
Archaeologists have explored several areas of Jefferson’s landscape. They have found the remains of a planting bed for shrubs and an area of densely planted trees on the north side of the house, planting holes on each of the two mounds, and a gate and hedge.
A major phase of the landscape excavation occurred in 1998 and 1999, when archaeologists dug along the banks of what is now the rectangular sunken lawn to collect evidence that would verify the 1812 memo.
They began on the east bank and uncovered surprising evidence, a shallow trench filled with rocks. The latter, known as a French drain, angled out from the house for 200 feet. Had Jefferson designed a bowling green that would have been a trapezoid, not a rectangle?
The following year, the archaeologists tackled the west bank. There, they found no French drain, but uncovered planting holes indicated the lawn's shape. As on the east bank, these holes occurred every six feet. Unlike the east bank, however, these plantings holes ran in a straight line south from the house. Going back to the east, they discovered planting holes in matching locations at the north and south end of the lawn. Apparently, the sunken lawn had changed design in Jefferson's time.
Archaeologists now believe that Jefferson initially designed a rectangular lawn with plantings near the base. Later, he decided to re-landscape the eastern half creating an asymmetrical shape. This asymmetry may mark changes that Jefferson had in mind for the landscape but never got around to completing after he added the east wing in 1814. A sunken lawn with both banks angling away from the house would have created the optical illusions of drawing the house or outlying landscape closer to one's eye depending on whether one stood at the edge of the lawn or on the south porch.
Or perhaps the asymmetry of the lawn was supposed to match the asymmetry of the house upon the wing's addition.
Besides the French drain and planting holes, archaeologists retrieved microscopic evidence. They collected bags of soil from the planting holes that were sent to laboratories for analysis. The laboratories separated the pollen and phytoliths (the silica remains of plants similar to animal skeletons) from the surrounding soil. Scientists were able to identify the origin of the pollen and phytoliths by examining their features. The evidence suggests that the banks of the south lawn were planted with some of the plants in the 1812 memo.
In 2002, archaeologists made a breakthrough in the search for Jefferson’s circular road when they uncovered eight tree holes believed to be associated with the paper mulberry trees that Jefferson directed be planted along the road’s edges. The circular road was the most important element in the geometry that united architecture and landscape in Jefferson’s scheme. Further excavation will be done in the future along the projected circle of the road to confirm the road’s location.
“[No] culture comparable to that of a garden... I am still devoted to the garden, but tho an old man, I am but a young gardener.”
Thomas Jefferson to Charles Willson Peale
Aug. 20, 1811