Costmary earned its place in American colonial gardens not for showiness but for usefulness. The long, silvery-green leaves smell of cool mint crossed with camphor and were famously pressed between Bible pages as fragrant bookmarks, lending the plant its other common name, Bible Leaf. Growing erect to 3 to 6 feet in zones 5 through 7, it spreads assertively by rhizome, so give it room at the back of an herb border and clip it back hard after flowering to keep the form tidy and the foliage full.

The yellow button flowers, arriving in corymbs from September into October, are cheerful in a small way but secondary to the aromatic leaves. Harvest foliage as needed through the growing season for teas, salads, and potpourri; the plant handles light cutting gracefully. In colder regions, it dies back hard in winter and resprouts reliably come spring. Because it produces only foliage when grown in shade, full sun is the non-negotiable part of the arrangement.