Forsythia is both the common name and botanical name of a plant genus belonging to the Olive (Oleacea) family. Known as レンギョウ in Japan. It is named after William Forsyth, and comprises six species of deciduous shrubs to 3-6 m tall, mostly native to Asia, but one native to southeastern Europe.
7 species of forsythia (rengyo in Japanese) were introduced to Western gardens from China and Japan in the 19th century and since then they have been popular shrubs because their brilliant golden blossoms make good cut flowers. They are also called Golden Bell Plants.
They have soft wooded stems branching from near the ground. They are full frost hardy and are not fussy about soil type. But they will only flower in climates where the winter temperatures go below freezing point.
Three main ones to look out for Forsythia intermedia (also called Border Forsythia), Forsythia suspensa (called Weeping Forsythia with dense arching slender branches) and Forythia viridissima (semi-evergreen deciduous species from China that is stiffer and less graceful but not as tall as other species).
The leaves are opposite, usually simple but sometimes trifoliate with a basal pair of small leaflets, and range from 4-12 cm long; the margin is serrated. The flowers are produced in the early spring before the leaves, bright yellow with four petals. The fruit is a dry capsule, containing several winged seeds.
Forsythias are used as food plants by the larvae of some butterflies including Brow-tail and the Gothic.
Western gardeners grow the shrub exclusively as an ornamental, but in China F. suspensa is used for culinary & medicinal purposes; & the garden hybrid makes a reasonable stand-in for the true species shrub. The yellow flowers are edible, used as garnish, though more for appearance than taste (they are somewhat bitter), & the tenderest young leaves are useful in salads & especially in soups.
The unripe fruit & seeds are crushed for use as an herbal medicine called lian qiao. Chinese herbalists recommend it for chills, fevers, headaches, & to help expel toxins from the body, the premise being that cleansing occurs by inducing farting. It is used topically for burns, infected injuries, carbuncles, rashes, & blemishes, some of the same uses long assumed in North America for a bark-extract of witchhazel.
In the absence of serious clinical trials, efficacy should be regarded at best debatable, though by no means improbable. A 1982 Japanese lab test, conducted by Nishibe et al in Tokyo, isolated the chemical component suspensaside from the crude Chinese drug, & found that it had a legitimate antibacterial action; this finding has been confirmed by later researchers. Another lab study conducted in 2001 by Rouf et al in Bangaladesh showed anti-inflammatory properties for the seed extract. This too is confirmed by several other researchers. A study by Schinella et al conducted in 2002 in Argentina showed an antioxidant function for the seed extract which was believed to explain the antibacterial properties of some of the chemical components.
Many similar laboratory analyses have provided suggestive results, but other studies, such as a 1991 mouse study by Yin et al in the Peoples Republic of China, indicate the chemical components of forsythia may be mutagenic, i.e., potentially cancer-causing. But no actual double-blind clinical trials have been conducted, so that the usefulness or harmfulness of lian qiao remains to be proven.
— Apr 3