This tree is usually 30-40' tall at maturity (rarely up to 60' tall),
consisting of a short trunk and a wide crown with ascending to widely
spreading branches. The crown is usually somewhat open and irregular.
On mature trees, the trunk is up to 1¼' across, consisting of flattened
gray ridges and shallow reddish brown furrows. The twigs are light
gray to reddish brown, more or less terete, with scattered small
lenticels. Young shoots are light green, terete, and glabrous to
minutely pubescent. Alternate compound leaves about ¾-1½' long occur
along the twigs and young shoots. These leaves are either
single-pinnate or partially bipinnate. Individual leaflets are usually
1½-4" long and 1-2½" across; they are lanceolate to ovate and either
coarsely toothed or shallowly cleft. On bipinnate leaves, there are 1-2
pairs of secondary leaflets below some of the primary leaflets. These
secondary leaflets are similar to the primary leaflets, except they are
smaller in size and more narrow in shape. The upper leaflet surface is
medium green and glabrous, while the lower leaflet surface is light
green and either glabrous or minutely pubescent along the central vein.
The leaflets usually have short petiolules (up to 1/8" or 3 mm. long),
some leaflets may be sessile. The petiolules are light green to light
yellow-green and glabrous to minutely pubescent. The central stalks
(rachises) of the compound leaves are light green to red and glabrous
to minutely pubescent.
Twigs occasionally terminate in panicles of flowers
about ¾-1½' long and at least one-half as much across. Each flower is
about ½" across, consisting of 4 yellow petals, 4 green sepals, 8
stamens, and a pistil with a single style. While a flower is in
bloom, the petals are widely spreading or recurved and they are
narrowly lanceolate to lanceolate in shape. The sepals are lanceolate
in shape and much shorter than the petals. At the base of each petal,
there is a pair of small scale-like appendages that are yellow to
orange-red. On the stamens, the lower halves of their filaments have
long hairs. Both the style and the stamens are strongly exerted. On
some trees, some of the flowers may be unisexual. The pedicels of the
flowers are green and either glabrous or minutely pubescent. The
peduncle and lateral stalks of each panicle are also green and either
glabrous or minutely pubescent.
The blooming period occurs during the
summer (usually mid- to late summer in Illinois) for about 2-4 weeks.
The flowers are mildly fragrant. Fertile flowers are replaced by
inflated seedpods that become 1½-2½" long at maturity. These seedpods
are obcordoid and strongly 3-lobed in shape; immature seedpods
are light green to bright red, while mature seedpods are light brown to
blackish brown. Each seedpod contains up to 3 seeds (1 seed per lobe).
Individual seeds are globoid or globoid-ovoid in shape and 6-8 mm. in
length. Because the seedpods are light-weight and inflated, they
can be blown about by the wind or float on water. The root system is
woody. This tree spreads by reseeding itself.
The preference is full or partial sun, well-drained conditions (moist
to dry-mesic), and soil containing loam, clay-loam, gravel, silt, or
sand. This tree is hardy to about Zone 6 (southern Illinois). In more
northern areas of the state, some cultivars of this tree can survive
several winters if they are planted in
sheltered situations near heated
The introduced Golden Rain Tree
rarely naturalizes in Illinois. So far, such trees have been observed
in only a single county in southern Illinois.
This is mainly because the Golden Rain Tree has trouble surviving the
relatively cold winters in Illinois, particularly in the central and
northern sections of the state. However, in many southeastern and
south-central states further to the south, such naturalized trees are
more abundant, and in some of these areas it is considered invasive.
The Golden Rain Tree is native to east Asia (primarily China &
Japan). It was introduced to North America as an ornamental landscape
tree. This tree naturalizes in such habitats as urban parks, roadsides,
vacant lots, edges of yards, and other disturbed areas. In east
Asia, it occurs in natural areas along seashores, secondary woodlands,
and open areas.
For North America, the
floral-faunal relationships for the Golden Rain Tree are not
well-understood. The showy flowers are cross-pollinated by bees and
probably other insects that seek nectar and pollen. A leaf-cutting bee
that has been introduced from Asia, Megachile sculpturalis
Resin Bee), is known to be one of the pollinators of this tree in the
southeastern United States. In North America, insects that feed
destructively on this tree appear to be few in number at the present
time. The larvae of a Buprestid beetle, Chrysobothris
, bore through the wood of dead branches
Missouri). Another insect, Jadera
(Golden Rain Tree Bug),
feeds on the seeds. The foliage of this tree is considered toxic to
horses, cattle, and probably other hoofed mammalian herbivores.
Near an office building in Urbana, Illinois.
This attractive small tree is the only species
of its genus
that has naturalized in Illinois. Two similar species are sometimes
cultivated in the United States: Koelreuteria
Tree) and Koelreuteria
(Chinese Rain Tree). These two trees
differ from the Golden Rain Tree (Koelreuteria
) by having
compound leaves that are fully bipinnate. The Golden Rain Tree, in
contrast, has compound leaves that are either single-pinnate or
partially bipinnate. The common name, Golden Rain Tree, refers to its
abundant yellow flowers falling like rain, creating a
carpet of yellow on the ground.