Alyssum is a genus of about 100–170 species of flowering plants in the family Brassicaceae, native to Europe, Asia, and northern Africa, with the highest species diversity in the Mediterranean region. The genus comprises annual and perennial herbaceous plants or (rarely) small shrubs, growing to 10–100 cm tall, with oblong-oval leaves. Alyssum flowers are characteristically small and grouped in terminal clusters; they are often yellow or white colored but can be pink or purple.
The genera Lobularia and Aurinia are closely related to Alyssum and were formerly included in it. The widely cultivated species popularly known as “sweet alyssum” is Lobularia maritima. The common rockery plant is Aurinia saxatilis.
Lobularia maritima is cultivated in gardens, with many horticultural varieties with purple or pink flowers. The plant is best planted in early spring, but requires little maintenance when growing. Although an annual, it may reseed in temperate climates. It will flower more profusely if spent blooms are trimmed. When grown in gardens, it is typically used as groundcover, as it rarely grows higher than 20 cm (8 in) tall. It is also grown in cracks in paving and walls, and is especially associated with coastal locations. It prefers partial shade, and is resistant to heat and drought. Plants with darker-colored flowers do better in cooler temperatures. Lobularia maritima has high drought and heat resistance.