Koelreuteria paniculata POTW

Of interest this week at Beal...
Golden Rain Tree
Koelreuteria paniculata
W. J. Beal
Botanical Garden
Family: the Soapberry family, Sapindaceae
Also called Varnish tree or Panicled Goldenraintree
In the first weeks of July, there are not many trees in full flower. The genus Koelreuteria
is comprised of from three to five very similar species found in East Asia, and is named
for Joseph Gottlieb Koelreuter, an 18th century German botanist. While they are all
quite similar, the Golden Rain Tree, Koelreuteria paniculata is only one that is hardy for
in our area (zone 5/6). The Golden Rain Tree is a fast-growing, short-lived species that
is tolerant of a wide variety of soils and moisture conditions and presents an attractive
display at least twice every growing season. In the early summer, the first weeks of July
at the W. J. Beal Botanical Garden, the tree is covered with large panicles (hence the
species epithet) of yellow flowers, some with a ring of red on the corolla. Later in autumn, the large pinnately compound leaves turn a rich yellow color until the leaves fall.
The showy flowers yield a yellow dye and are followed by papery three-valved lanternlike fruit. The seeds enclosed within the lantern-like bracts have a history of being
strung as beads. The tender young spring shoots and leaves have a traditional use as
a cooked green, and the mature leaves have provided a black dye for the cultures in
its range. The growth rate is quite fast, especially during the ealiest years. Its wood,
although hard is quite brittle and so this small tree benefits from a sheltered location
during high winds.
The phytochemistry of Koelreuteria paniculata is known to be quite diverse and it has
a medicinal reputation that includes antioxidant and anti-tumor activity but its actual
inventory of compounds is still being elucidated. In 2002, Lin et al., Peking University,
discovered a novel pseudo sesquiterpenoid with a previously unknown structure they
called “paniculoid 1.”
The seeds have been demonstrated to contain both flavonoids and galloyl derivatives
that suggest its possible utility as an insecticidal agent. A decoction of the flowers has
As Golden Rain Tree’s flowers age, the corollas of some of
the oldest flowers turn red at the proximal end of the petals.
been used as an ophthalmic rinse for the eyes. The leaves have provided an extensive
inventory of phenolic compounds in addition to at least two flavonol glycosides.
In China, it has often been a symbol used to mark the graves of scholars. Whether it
gets the name Golden Rain Tree from its fall leaf color, or from the carpet of golden
flowers that accumulate beneath its summer panicles is unclear. Its papery seed capsules are effective in seed dispersal, and many seedlings appear under and around its
branches.