The Hyssop was an herb in the Mediterranean region.  It grows about 1.5 feet tall with summer blooms in different colors such as violet, red and white.  It was known for its flavoring and medicinal properties for both physical and topical, most often used for skin balm.  We read about the Hyssop branch several times in the Old and New Testaments often when it comes to the process of being cleansed often when speaking about leprosy. Both Leviticus 14 and later in Numbers give instruction to lepers to use Hyssop for both the cleansing of their bodies and of their homes.