Giant Hyssop Seeds

Agastache foeniculum

Giant Hyssop is a tall, striking perennial herb in the mint family, valued for its towering stems, aromatic foliage, and vibrant flower spikes. Mature plants can reach 6 to 7 feet or more, forming dense clumps approximately 2 to 3 feet wide. Its opposite, serrated leaves release a sweet anise or licorice fragrance when brushed or crushed, adding a sensory dimension to any garden. The upright form provides dramatic vertical structure, making it a focal point in borders, cottage gardens, and naturalised landscapes.

From mid-summer through early fall, Giant Hyssop produces dense spikes of tubular flowers in shades of purple, lavender, pink, and occasionally white, which attract bees, butterflies, and hummingbirds. To encourage long-lasting blooms, deadheading spent flowers can be performed, while cutting back foliage in late fall or early spring promotes vigorous new growth. The plant thrives in full sun but tolerates partial shade, and prefers well-draining soil, including sandy, loamy, or slightly alkaline types. It is moderately drought-tolerant once established, though regular watering during dry spells supports optimal growth.

Giant Hyssop can be propagated by seed, division, or softwood cuttings, with seeds started indoors 6–8 weeks before the last frost or sown outdoors after frost risk passes. Clumps may self-seed under favourable conditions, forming new plants nearby. Spacing of 2–3 feet apart ensures strong stems and reduces the risk of disease. The plant is generally pest- and disease-resistant, with deer and rabbits rarely feeding on it. Overly wet conditions can occasionally promote fungal issues, so proper soil drainage is essential.

Both the leaves and flowers are edible, with a mild, sweet herbal flavour suitable for herbal teas, syrups, salads, and desserts. Historically, Giant Hyssop has been used as a medicinal herb, supporting respiratory health, aiding digestion, and providing mild antimicrobial effects. Its combination of dramatic flower spikes, aromatic foliage, edible and medicinal qualities, and wildlife support makes it a versatile plant that provides colour, fragrance, ecological value, and vertical interest in gardens, pollinator plantings, herb gardens, and naturalised meadows.