Plant of the month: May
Koelreuteria paniculata in the family Sapindaceae can be found on the Main Lawn just behind the box hedge.
This stunning tree has leaves that open in shades of pinky orange and is commonly known as the ‘Golden – rain tree’. The leaves turn green as the season progresses and by autumn they are butter-yellow. Leaves are arranged alternately on the stem and are bi-pinnate, meaning each leaf is divided a second time, making a compound leaf (the definition of bi-pinnate is ‘pinnate with the primary leaflets being pinnate again’).
Flowers are small and yellow arranged in a large pyramidal panicle, these can be followed in a good year by bladder like seed pods containing black seeds. The bladder ripens to pink or red and its final size is about 2 inches.
Our tree at the Birmingham Botanical Gardens is fairly young but already has a presence at this time of year, showing off its gloriously coloured foliage against a bright blue sky. Eventually the tree could reach about 30 feet in height and spread.
The tree is hardy as long as the wood is ripened over the summer, as it would be in its native habitat of China and Korea.
Koelreuterias need fertile, well drained soil in full sun. Pruning is only necessary to remove damaged or dead wood in the winter. These trees are usually pest and disease free, but have become invasive in some states of Eastern America.
The name Koelreuteria is used in honour of Professor Joseph Gottlieb Koelreuteria, a pioneer of experimental plant hybridisation in Karlsruhe, Germany in the 1700’s.