Horehound (Marrubium vulgare) is a perennial herb that belongs to the mint family. Horehound plants are drought-tolerant and hardy down to minus 25 degrees Fahrenheit, thriving in full sunlight and well-draining soils. Horehound plants are often grown for making teas, candies and cough drops from their leaves and flowers. The horehound's blossoms and foliage contain many major vitamins, including essential fatty acids, potassium and iron. Horehound herbs are easy to grow and harvest, growing best during the warmer spring and summer months.
Water your horehound plant moderately once per week during summer, only when the soil dries out slightly. Don't allow the horehound plant sit in soggy or waterlogged soil.
Feed your horehound plant with an all-purpose garden fertilizer in early spring, according to the recommended dosage on the label. Apply another dose of a liquid nitrogen fertilizer after the harvest.
Cut off the horehound plant's flowers before they produce seeds to prevent the plant from spreading invasively. Shallowly hoe around the horehound plants to control weeds.
Harvest the horehound's leaves by picking them off the plant, removing only one-third of the leaves during the first year. After the first year, harvest the leaves and flowers at the peak of blooming. Tie the leaves and flowers together, and hang the bundle indoors in a shaded place to dry.