Annual herbs live for one growing season. They are usually planted in the spring around the last expected hard frost and are killed off by the first hard frost in the fall. Some common annuals are basil, dill and summer savory. Basil grows to about 1 1/2 feet tall and can be used fresh or dried. Dill plants grow to between 2 and 3 feet tall. Dill seeds and leaves are used in pickling. Summer savory grows to 1 1/2 feet tall and can be used fresh or dried.
Biennial herbs live for two growing seasons. They are planted in the spring, grow the first season and bloom the second season. Caraway grows to a height of 30 inches. It is grown for caraway seeds, which are not harvested until after the plant blooms the second year. Parsley is an ideal herb for beginners to grow. It is a biennial that is grown as an annual because it blooms the second year, which causes the leaves to lose their flavor. Parsley grows to only 1 foot tall and should be used fresh.
Perennial herbs grow back year after year. They are generally planted in the spring around the last expected frost. Sage grows to a height of 2 to 3 feet. It should not be harvested until the second year of growth to allow the plant to become well-established. Sweet marjoram is a perennial in very warm Southern climates but dies off in the winter in cooler climates where it is grown as an annual. It grows to a height of about 1 foot and can be used fresh or dried. Thyme grows to only 6 to 12 inches tall and should be harvested sparingly until the second year.
Evergreen herbs grow year-round in warm Southern climates. In cooler climates, they can be brought into the house for the winter and set back out in the garden in the spring. Rosemary can grow to between 4 and 6 feet tall in warm climates but will stay smaller in cooler climates or when planted in a pot. It may be harvested as needed but no more than one-third of the plant should be taken at one time. Winter savory is an evergreen herb in areas south of USDA zone 5. In zones 5 and below, it is a hardy perennial. It grows to a mature height of 2 feet or less. The leaves may be harvested anytime and used fresh or dried.