Rosemary (Rosmarinus officianalis) was a popular Christmas decoration in the 19th century. St. Thomas More said of it: "tis the herb sacred to remembrance and therefore to friendship.' The choirboys of Ripon carried it on Christmas morning as a sign of redemption. A number of legends link rosemary with Christmas: it is said that the herb's purple hue derives from the robes of the Virgin Mary; that it's aroma comes from the swaddling clothes of Christ; that the plant will never grown taller than Christ; and if a rosemary bush lives longer than Christ's 33 years, it will branch outwards not upwards. Because of these associations with Mary, it is said that rosemary grows best 'where the mistress is master.'
-From Schott's Almanac 2008 Page-A-Day calendar.