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Diervilla is a plant genus that is part of the Caprifoliaceae family. It consists of three species of deciduous perennial shrubs that are native to the eastern United States and Canada. D. sessilifolia is referred to as the southern bush honeysuckle, while D. lonicera is commonly known as the northern bush honeysuckle. The third species, D. rivularis is called the mountain bush honeysuckle. All three plants grow between three and five feet (about 1-1.5 m) in height and feature two-lipped yellow flowers that generally bloom from July to August.
The flowers are a half inch (about 1.2 cm) in diameter and are arranged in a cluster. Small capsule shaped, brown fruits replace the flowers. By the fall, all the leaves and fruits have fallen off, revealing the brown, striped bark.
In the spring time, the shrub grows vigorously, producing a dense collection of shoots that will bloom in the summer. The summer foliage of Diervilla sessilifolia consists of dark green lance-shaped leaves that grow in opposite directions from the branches. Typically, the leaves are 2-6 inches (about 5-15 cm) in length and 1-3 inches (about 2.5-7.5 cm) wide.
Bush honeysuckles are tolerant of most soil conditions and typically grow well in full or partial sunlight. Pruning is required during the growing season to maintain an uniform shape. Old and decaying branches should be removed as well.
The best method for propagating diervilla shrubs is through softwood cuttings. Usually, if the stem breaks from bending, instead of becoming limp, it is ready to be cut. Typically, the cutting should be 3-5 inches (about 7.5-12.5 cm) long and should be taken one inch (2.54 cm) below the second leaf node. The cutting is then placed in a pot with a fertile medium to allow root development. Once it has grown large enough, it can be transplanted outdoors.
Diervilla shrubs are typically used in landscaping as foundation plants, usually on the corners of houses or at the entryways. Several diervilla shrubs can be planted together as well, especially in empty yards. Also, diervilla shrubs blend nicely with other types of shrubs and plants that make up long borders.
The appealing nature of diervilla shrubs can be hindered by certain pests and diseases. Aphids are a small insect that can cause the yellowing and curling of leaves. They also leave behind a sticky substance that attracts fungal spores. Sooty mold fungus and leaf spot are two fungal infections that can disfigure the natural appearance of the shrub. Regular water spraying and routine application of fungicide can reduce the risk of infestation.