Alyssum is a popular, low-growing flowering plant widely recognized for its blanket of tiny, fragrant blooms. The common name Alyssum is applied to several different species, which causes confusion about its life cycle. Whether the plant is classified as an annual or a perennial depends entirely on its specific botanical identity and the climate in which it is grown.
Understanding the Two Alyssum Groups
The ambiguity surrounding Alyssum’s life span is primarily due to two distinct groups sold under the same common name. The first is Sweet Alyssum (Lobularia maritima), which is the most common variety found in garden centers and is generally treated as an annual in most temperate climates. The second group is Basket-of-Gold Alyssum (Aurinia saxatilis), which is a completely separate plant from a different genus. This species is a dependable, long-lived perennial, capable of surviving year after year in colder regions.
The distinction between the two plants is important because their care and winter survival capabilities are vastly different. Sweet Alyssum (Lobularia maritima) is native to the Mediterranean region and is highly susceptible to hard frosts. It is typically marketed for use in zones 3 through 8, where it survives for only a single growing season. Basket-of-Gold (Aurinia saxatilis), however, is a hardy perennial best suited for zones 4 through 8, where it reliably returns each spring.
Sweet Alyssum: An Annual by Default
Sweet Alyssum (Lobularia maritima) is characterized by its rapid growth, forming low-mounding, spreading carpets of foliage. The tiny, four-petaled flowers are intensely sweet-smelling, coming in shades of white, pink, purple, or lavender. Due to its Mediterranean origins, this plant is not genetically adapted to survive the deep freezes of a typical winter in colder regions. It quickly completes its life cycle from seed to flower to seed within a single growing season, which is the definition of an annual plant.
Gardeners in cooler areas must replant Sweet Alyssum every spring after the danger of frost has passed. Its main appeal is its ability to produce a continuous abundance of blossoms from late spring until the first heavy frost. This long bloom period makes it a popular choice for edging, containers, and hanging baskets. The plant’s shallow root system thrives in full sun to partial shade and requires consistently moist, but well-drained, soil to prevent the onset of root rot.
While it is treated as an annual in most places, Lobularia maritima is technically a tender or short-lived perennial in its native, frost-free habitats. In very warm climates, such as USDA zones 9 through 11, it can sometimes survive the mild winter and continue growing for multiple seasons. Even where it is killed by winter cold, Sweet Alyssum is a prolific self-seeder, dropping small, yellowish seeds that often germinate the following spring. To maximize the flowering of this species throughout the summer, spent flower heads should be trimmed or “deadheaded” to encourage new growth and prevent the plant from putting all its energy into seed production.
Basket-of-Gold Alyssum: A True Perennial
The plant known as Basket-of-Gold Alyssum (Aurinia saxatilis) is a true perennial species that offers a very different garden experience. Unlike its fragrant cousin, this plant features distinct bright golden-yellow flowers and gray-green, semi-evergreen foliage. It possesses a woody root structure and is reliably hardy, surviving the winter dormant period in climates down to USDA Zone 4.
Aurinia saxatilis is naturally adapted to survive in harsh, rocky environments, making it an ideal choice for rock gardens, stone walls, and dry slopes. Its preference is for very sharp drainage, often tolerating poor or sandy soils much better than rich, moist ones. The plant’s flowering period is concentrated in the spring and early summer, where it forms a dense mat of bright color.
To maintain an attractive form, it should be pruned back by up to half of its size immediately after the spring bloom has finished. This post-flowering cut encourages new, compact growth and prevents the plant from becoming leggy or sparse. Providing excellent drainage is the single most important factor for its perennial survival, as waterlogged soil during the winter is a common cause of its decline. This hardy species offers a burst of color in the spring and remains an attractive, drought-tolerant groundcover for the rest of the year.