Theatrum botanicum : the theater of plants or an herball of a large extent; containung thereina more ample andexat history and declaration of the physicall herbs and plants.

Originally published in 1640. Parkinson held the position of Botanicus Regius Primarius to Charles I and Apothecary to James I. Parkinson's Theatrum Botanicum is the largest of the English herbals (nearly double that of the first edition of Gerard's). "While Parkinson's reputation was established by the appearance of his Paradisus in 1629, the latter was overshadowed by the publication in 1640 of what was his much greater work, the Theatrum Botanicum . This digest attempted the description of nearly 4,000 plants, almost 1000 more than were contained in Johnson's edition of Gerard. The descriptions in many instances are new and great care was exercised to secure accuracy in indicating localities."- Green. The Botanicum was the most complete and beautifully presented English botanical treatise of its day. "One of the two main pillars of botany in England at the time of Ray" (Henrey). Parkinson's work, although based on Matthias L'Obel's works, was in large part original. It was the first work to describe 33 native plants, 13 of which grew near Parkinson's Middlesex home. Some of these plants, such as the Welsh poppy, the Strawberry Tree and the Lady's Slipper, were very common but had gone unnoticed or at least unrecorded. He intended the book to be a reliable guide for apothecaries, and it remained so for more than a hundred years after his death.