Heirloom Herb. Sweet Marjoram produces leaves that are aromatic, mild, sweet and absolutely delicious in dressings, soups and salads. It is said that this herb is a must when cooking strong meats. The plant is a vigorous grower, often reaching 60 cm (2′) in height. Also known as Pot Marjoram, French Marjoram or Cretan Oregano. As sweet marjoram is a very tender perennial hardy only to Zone 7, it is almost always grown as an annual.