Peggy Cornett at Thomas Jefferson's Monticello tells us that
The hardy annual Larkspur, Consolida ajacis, re-seeds abundantly in the Monticello Flower Gardens. Jefferson noted Larkspur blooming at Shadwell in July 1767, thought it suitable for naturalizing at Monticello "in the open ground on the west" in 1771, and sowed seed around his Roundabout flower border on April 8, 1810.
Larkspur, Consolida ajacis