The blue potato bush is a perennial evergreen shrub. It is a tropical plant and very heat-tolerant, but can survive in cooler climates as well. Its showy flowers and berries make it a good choice for an ornamental bush. Seeds from the bush are poisonous, and no part of the plant should be ingested.
Blue potato bushes are native to Paraguay and Argentina. They are sometimes also called Paraguay nightshade because of their origins. Blue solanum shrub is another name for the plant. Its scientific categorization is Lycianthes rantonnetii. Blue potato bushes belong to the Solanum family. Biologists classfiy the common potato, Solanum tuberosum, which is in the same family.
These shrubs can grow up to 8 feet (2.4 meters) tall and can spread as much as 6 feet (1.8 meters) wide. They are typically very bushy, with many branches. The plants can also be pruned and trained to grow as small trees.
The evergreen leaves of the blue potato bush are medium to dark green. They can be up to 4 inches (10 centimeters) long, and are usually oval-shaped and somewhat pointed. The leaves usually also have wavy edges.
As the name implies, the blue potato bush produces dark blue or violet flowers that grow in clusters. The centers of these blooms are light blue or yellow. The flowers are round and usually 0.5 to 1 inch (1.25 to 2.5 centimeters) in diameter. The shrubs flower in summer and fall in more temperate climates, but where it is warm enough they will bloom year-round. Berries from the plants are red, oval, and up to 1-inch (2.5 centimeters) long.
The blue potato bush has several different varieties, which have slight variations in their flowers and leaves. The Royal Robe potato bush has darker, bluish-purple flowers, while the Outremer has wider flowers that are a more pure blue color. Variegata Aurea, as the name implies, is a variety that has variegated leaves.
Being from tropical climates, the blue potato bush requires constantly moist soil, but they should not be watered too frequently. The plants prefer neutral or slightly acidic soils with lots of organic matter, and should be planted in full sunlight. They can withstand temperatures down to 15°F (-9.4°C), although they should be protected from frosts. In colder climates, the shrubs act like deciduous plants, freezing in the winter but growing again once temperatures warm in the spring.