Senna corymbosa

Senna corymbosa, also known as Bush Senna, is a hardy shrub prized for its tropical appearance that creates themed scenes. It is medium sized, almost as wide as it is tall, with beautifully cut, vibrant green foliage that persists if the winter is mild. This Senna is especially appreciated for its bright yellow flowering that extends from mid-summer to autumn. It prefers sunny exposures, withstands dry conditions well and needs well-drained soil. It is hardy down to -8°C and can be grown in containers in regions with very cold winters, allowing it to be brought indoors when it freezes.

Senna is a member of the Fabaceae family (formerly known as Leguminosae), the third most prolific in terms of species (approximately 19,500!). It includes food and forage plants, as well as numerous ornamental plants such as Albizia, Wisteria, or Honey Locust. The Cassia and Senna genera, which have been subject to species reclassification from one to the other, together account for several hundred species. Cassia mainly consists of trees and shrubs, with a few herbaceous plants.
Senna corymbosa is native to Argentina and Uruguay, hence its common name of Argentine Senna. This evergreen shrub has a slightly upright habit but eventually forms a ball shape that is almost as wide as it is tall. It generally reaches 2m high with a spread of 1.75m but can grow up to 3m tall or even taller under favourable conditions. You can prune it to the shape of a small tree with a short trunk. It has beautiful compound leaves with an even number of leaflets (often 8), arranged in pairs on either side. The leaves are a vibrant green, slightly glossy, and often give it a slightly tousled appearance as they spread in all directions.
During July, earlier or later depending on the geographical area, very bright yellow flowers appear, which pleasantly contrast with the darker foliage. The small flowers (about 3sm) are simple but abundant, with 5 petals and vaguely resembling buttercups. They bloom from July to October or even November, making this one of the best flowering shrubs for late summer.
It is slightly hardier than the neighbouring species Cassia x floribunda and once rooted, can withstand temperatures down to -8°C and sometimes -10°C, provided it is planted in very well-drained soil. It also withstands dry conditions very well and appreciates full sun, making it a valuable plant for the Mediterranean coast, where it is abundantly planted. It will also survive on the Atlantic coast, but elsewhere it should be kept in containers and overwintered during the cold season.

Senna corymbosa will be perfect for creating an exotic scene in mild climates, with other plants whose silhouette evokes distant lands. Caesalpinia gilliesii, or Bird of Paradise, with its finely cut foliage and yellow flowers with long red stamens, will be a great companion. Callistemon, the famous bottlebrush with flowers that come in red, purple, or white depending on the variety, will also be well-suited alongside your Cassia. And to add a touch of blue, Plumbago capensis or Solanum rantonetti will be well-adapted in milder climates.