Family: Golden-rain Tree
Golden-rain Tree is a slow-growing tree that will give multi-season interest to broad streetscapes. Eventually, it will grow to 10m tall, with an irregular, intricately-branched canopy, elegant pinnately-compound foliage and chains of yellow flowers in the summer. The autumn foliage colour is an added bonus; in most places it will be bronze-to-gold, holding on the tree until mid-May. The bark is finely-fissured, and becomes very interesting on mature trees.
Koelreuteria paniculata comes from rocky outcrops in east Asia, and is relatively drought-tolerant in Australia. In Adelaide and a few Melbourne streets, K. paniculata grows into upright-oval trees of excellent shape. Seemingly, if the plants have adequate irrigation for establishment, they will grow relatively well without later summer irrigation. They grow best in full sun, and tolerate both acidic and alkaline soils.
In Melbourne, poor-quality K. paniculata are also evident. In examining the sites where these trees are grown, typically the trees are in shade, have not been well-established, and the trees were poor quality when planted. In order to have establishment within 2 years, it seems necessary to plant a tree with an excellent root-to-shoot ratio: in a 40 or 50 litre container, trees should not be taller than 1.5m to have the appropriate ratio.
K. paniculata is not a tree for shady, poorly-managed sites. It also will not be the fast-growing tree for some urban areas; instead, K. paniculata is an elegant, slow-growing tree suitable for residential areas where fast growth is not essential.
Typical mature height: 7-10m
Useful in: avenues, broad streetscapes
Sites for best growth: acid or alkaline sites, in full sun