THE TREE OF THE MONTH FOR AUGUST 2016: PRIDE OF INDIA (AKA GOLDEN RAIN TREE)

By Karelj (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons

Rather unhelpfully, the Pride of India tree comes from China (where it has often been a symbol used to mark the graves of scholars). Equally confusingly, its other common name, Goldenrain tree, is shared with Laburnum; so I tend to stick with the Latin - Koelreuteria paniculata.

Koelreuteria is another tree that has to be on the short list for smaller sunny gardens. It has attractive foliage, provides a striking mid-summer floral display, and has fiery autumn colour.

It belongs to the Soapberry family (Sapindaceae) which has lately been expanded to include the Maples and Horse Chestnuts. It is hardy, tolerates a wide range of soils, drought and air pollution, making it suitable for many locations - including as a street tree. The wood is quite brittle though and some shelter can help.  The tree was introduced in 1763 and is said to have first been cultivated in Croombe, in Worcestershire. It is named after J. G. Koelreuter, a professor of botany at Karlsruhe (1733-1806).

The tree can attain 30 - 60 feet in height and can be rather gaunt in habit when young, becoming more compact with age.

Young tree with flowers just emerging at the end of July. Canford School

Lobed pinnate leaves. Image by By peganum from Small Dole, England [CC BY-SA 2.0 http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons

The large compound leaves can be 6-18 inches long with individual leaflets of 1-4 inches length. Leaflets are deeply lobed, and very occasionally so deeply cut that they are technically bi-pinnate (the species K. bipinnata is truly bi-pinnate).

The leaves emerge a delicate and attractive pinky bronze and give a showy and fiery autumn display.

Koelreuteria flowers are particularly distinctive. Tens of thousands of bright yellow flowers,  some with a ring of red on the corolla, adorn the tree in late July and August - these being most spectacular during hot summers. The flowers are arranged in large terminal pyramidal panicles, above and beyond the crown, sometimes over a foot long - though gardening writer Christopher Lloyd commented that you need to be careful in selecting a good flowering strain as otherwise "they can be squinny little runts".

The flowers give way to the fruits which are green, turning to pinky-orange, fading to brown, tri-lobed papery and lantern-like - a feature in themselves. The Chinese used to make necklaces from the seeds and the flowers were used medicinally.

The lanterns contain 3 black pea-sized seeds from which germinate readily. The seeds have been demonstrated to contain both flavonoids and galloyl derivatives that suggest its possible use as an insecticidal agent

Papery lantern fruits. Image by mauroguanandi https://creativecommons.org/licenses/by/2.0/

The phytochemistry of Koelreuteria paniculata is known to be quite diverse and it has a medicinal reputation that includes antioxidant and anti-tumor activity.

The tolerance of Koelreuteria to a wide range of conditions and its ability to set viable seed mean that it is becoming invasive in Florida and Hawaii where it can out-compete native vegetation. Who knows, a touch more global warming and it will begin a march through our woodlands?