Of interest this week at Beal...

Golden Rain Tree Koelreuteria paniculata Family: the Soapberry family, Sapindaceae Also called Varnish tree or Panicled Goldenraintree W. J. Beal Botanical Garden 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 au- tumn, 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 lantern- like 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 cap- sules are effective in seed dispersal, and many seedlings appear under and around its branches.