A clump is a cluster of trees or shrubs intentionally planted or left growing on a pleasure grounds to relieve the monotony of open ground. A clump could refer to a tuft of trees or shrubs or to any compact mass or patch of any growing plant in the grounds.
In 1789, Jedidiah Morse's American Geography described the grounds around George Washington's Mount Vernon in Virginia, "the lands...ornamented with littles copcies, circular clumps and single trees."
On his travels through South Carolina in 1796, Duc de Francois LaRochefoucauld-Liancourt described Drayton Hall near Charleston, "The Garden here is better laid out...In order to have a fine garden, you have nothing to do but to let the trees remain standing here and there, or in clumps, to plant bushes in front of them, and arrange the trees according to their height. Dr. Drayton's father...began to lay out the garden on this principle; and his son...has pursued the same plan."
In the 1790s, Isaac Weld noted on his travels through the United States, "A neat boarded little mansion painted white, together with offices, were situated on a small eminence...A small lawn laid down in grass appeared in front of the house, ornamented with clumps of pines...large clumps of trees were left adjoining to the house."
Alexander Hamilton's 1802 notes for Hamilton Grange called for, "Some laurel should be planted along the edge of the shrubbery and round the clump of trees near the house."
In 1804, Thomas Jefferson noted of the grounds around Monticello, Virginia, "This must be broken by clumps of thicket, as the open grounds of the English are broken by clumps of trees."
John Gardiner and David Hepburn wrote in their 1804 American Gardener published in Washington, District of Columbia, "In forming a shrubbery, plant the lowest shrubs in front of clumps, and the tallest most backward, three to six feet apart, according to the bulk the shrubs grow. They will thus appear to most advantage."
Bernard M'Mahon agreed in his 1806 American Gardener's Calendar published in Philadelphia, Pennsylvania, "In designs for a Pleasure ground...winding walks, all bounded with plantations of trees, shrubs, and flowers, in various clumps...For instance, a grand and spacious open lawn, of grass ground, is generally first presented immediately to the front of the mansion...having each side embellished with plantations of shrubbery, clumps, thickets, &c in sweeps, curves, and projections toward the lawn."