Allamanda is a genus of tropical, evergreen, flowering plants in the dogbane family (Apocynaceae), known for their showy, trumpet-shaped flowers, often bright yellow, but also available in shades of pink and purple. 

Here's a more detailed description:

General Characteristics:

Growth Habit: Allamanda species are primarily woody climbers or shrubs, often cultivated for their ornamental value. 

Leaves: They have leathery, glossy green leaves, typically arranged in whorls of three or four along the stems. 

Flowers: The flowers are large and trumpet-shaped, with five petals, and can be found in various colors, including yellow, pink, and purple. 

Fruit: The fruit is a prickly capsule that splits open to release winged seeds. 

Sap: Allamanda plants contain milky sap. 

Specific Species and Cultivars:

Allamanda cathartica (Golden Trumpet or Common Allamanda): This is a common species known for its bright yellow flowers. 

Allamanda blanchetii (Purple Allamanda): This species features purplish-pink to violet trumpet flowers. 

Allamanda schottii (Bush Allamanda): This shrub bears large yellow flowers for much of the year. 

Allamanda cathartica 'Alba': A cultivar with white, fragrant flowers. 

Allamanda cathartica 'Compacta': A dwarf variety. 

Cultivation:

Climate: Allamanda plants thrive in warm, sunny conditions and are native to tropical regions. 

Soil: They prefer well-draining soil rich in organic matter. 

Watering: Keep the soil consistently moist, especially during the growing season, but reduce watering in winter. 

Sunlight: Allamandas require at least 6 hours of direct sunlight daily. 

Pruning: Regular pruning helps to maintain the shape and size of the plant and encourages branching. 

Support: Climbing varieties need support, such as trellises or arbors. 

Uses:

Ornamental: Allamanda plants are popular for their striking blooms and glossy foliage, adding a touch of tropical elegance to gardens and landscapes. 

Traditional Medicine: Some parts of the plant have been used in traditional medicine. 

Natural Dye: The flowers can be used to extract a natural dye.