Koelreuteria paniculata

Only few trees in Central European climate can boast of summer flowering while all other shrubs and trees have only leaves after their spring flowers have vanished. Golden-rain tree is one of the few. It is a deciduous tree native to China and naturally occurring in Japan and Korea, too. It was first described in 1772 by Russian naturalist Erik Gustavovich Laxmann (1737-1796) and the species was named after his contemporary, German botanist Joseph Gottlieb Koelreuter (1733-1806), whom he met during his studies in St. Petersburg in Russia. Reports of the very first tree imported into Europe are from Great Britain in 1763, where it was planted in the gardens of Croome in Worcestershire, and it was apparently this very tree that Laxmann had available for examination. In Czechia, according to Braun's list, our first tree was planted in Královská obora (the Royal Park) in Prague around 1835, and mature specimens adorn parks and streets of Prague 1 and 2 until today.

The species of golden-rain tree begins to bloom around mid-summer and makes beautiful, 30 to 40 cm long panicles, which are abundantly covered with small, deep yellow flowers with less conspicuous red eye. They bloom for up to 4 weeks and some of the latest flowers often appear along with attractive seedpods that look like hanging lanterns that ripen to bright salmon pink colour. The seeds are rather viable and germinate easily on unmaintained areas. In countries with a hot climate they form thickets over time which is why they are somewhere classified invasive, e.g., S.E. USA.

Another highlight are the exotic pinnate leaves whose individual leaflets are unevenly notched at margins, making the compound foliage look like lace. They are 20-45 cm long, exceptionally bipinnate, and emerge among the latest of all deciduous trees (albizia, campsis, hibiscus). Young leaves are pink or copper orange in spring, ripen to bright green in summer, and turn either fiery orange and red or just golden yellow in autumn. Their autumn colour is determined by the genetic information which may vary seed to seed. Still, by using highly acidic soil you can enhance autumn colours.

Golden-rain tree grows moderately to fast (30-40 cm per year), naturally into a multi-stemmed shrub, but in nurseries it is more often trained into a single-stemmed alley tree with a strong leader. The canopy is almost spherical to dome-shaped with age. Pruning is not necessary but can be done in early spring before the sap rises but after the danger of strong frost. Hard pruning is also possible – leaving only some 20-30 cm of previous year's branches will result in rapid growth of long canes with extra-large leaves but may endanger profuse flowering if cut too hard. The canopy casts a pleasant, not too dark shade, allowing the cultivation of semi-shade loving plants under it.

Although this tree belongs among small to medium-sized, its cultivation in private landscapes is still quite rare and certainly deserves a wider spread. In gardens its usual height and spread is between 5 and 7 m, while in parks and arboretums with unlimited root space it can grow twice as much. It can take almost any but waterlogged soil, it tolerates road salt and urban pollution. For abundant flowering, it needs a sunny and warm place and a nice summer. Every tree needs a strong support for the first 3-4 years from transplanting and no turf above its roots. Plants older than 3 years are fully hardy to min. -30 °C (USDA zone 5) and can allegedly cope with short spells down to -34 °C temporarily.

Last update 08-12-2008; 04-10-2014; 14-02-2024