Wisteria (chinese / japanese)

Occurrence and distribution: Chinese and Japanese wisteria are found in Europe and North America. They are used exclusively as ornamentals. In the United States, an indigenous variety exists: the American wisteria (Wisteria frutescens (L.) Poir.). The plants are often grown as greenery in parks or around houses. Various varieties and cultivars are available from specialist shops. The natural distribution of wisteria is limited to China and Japan. There it can be found in riparian forests and along riverbanks. In Europe, the plant has been considered an ornamental since 1816 [citation needed].

Growth habit: It is a climbing plant (climbing shrub) that quickly becomes woody on the main branch (like a liana). It is exclusively deciduous. The plant can reach a height of 6 to 10 metres (rarely up to 20-30 metres). In winter only the woody parts of the plant remain. In spring and summer light green secondary shoots develop. These help the plant to spread further by ‘twining’ or seeking new host plants.

Leaves: The leaves are often arranged in opposite pairs on the thinner secondary shoots. Individual leaves are pinnate. The edge of the leaflets is smooth. The upper side of the leaves is light yellow-green in colour when young, later the upper side of the leaves turns light green.

Flowers: Wisteria produces terminal, large clusters of flowers at the end of the side shoots. These hang downwards away from the plant. Each raceme consists of a large number of blue/light purple flowers. The flowers are zygomorphic and have a double perianth. It is pollinated exclusively by the blue carpenter bee. It is mainly found on the chinese wisteria (Wisteria sinensis) which is often planted in gardens. Chinese wisteria flowers from April to May. Japanese wisteria flowers in early to mid spring.

Fruits: The fruits consist of one to multi-seeded legumes. These are elongated and have velvety hairs on the surface (seeds without hairs also occur less frequently). The legumes of the chinese wisteria are greenish in colour, covered with light velvety hairs and have a flat structure. Legumes of the Japanese wisteria are dark brown to grey-brown in colour. The fruits of both species ripen in June to July. The second flowering usually also produces seeds, but these no longer ripen in winter and often only open the following spring.

Further information on the growth habit: Chinese wisteria is a left-hand twiner (i.e. the climbing plant twines anti-clockwise around the host plant). The related Japanese wisteria, on the other hand, is a right-hand twiner (usually with several stems)!

Detailed description of flowers: In some cultivated forms the petals may be white. In other species the colour ranges from blue to light purple to dark purple. The upper fused petals (vane) are larger than the lower flower parts (boat) with the wings (flower parts protruding from the side of the boat). In total there are five petals (called boat flowers). Inside the boat (lower part of the flower) is the ovary with the pistil (which is smooth). Around the pistil are the 10 stamens (usually fused in pairs). The flowers are hermaphroditic inflorescences. The blue carpenter bee is the only pollinator of the flower, as it is the only one that can trigger the pollination mechanism of the flowers (due to its weight).

Distinguishing between the two most common wisteria species: The flowers of both wisteria species are described in the literature as fragrant. The flowers of the japanese wisteria (Wisteria floribunda) are described as smaller, stronger smelling and in loose racemes. [Bulletin of Popular Information (Arnold Arboretum, Harvard University) 3, no. 8 (1917): page 30; http://www.jstor.org/stable/42960658]

Detailed description of the seeds: As the fruit ripens, the individual seed chambers thicken. When fully ripe, the seed capsules burst. This results in the sudden dispersal of seeds over several metres. The burst seed capsules have a “corkscrew” shape. They are shiny on the inside. The individual seeds are dark brown to black and roundish. The surface is smooth to wrinkled.

Toxicity of the plant: Wisteria is a poisonous plant that is toxic in all parts! Special care must be taken when handling the plant. Gloves should always be worn when cutting the plant. Do not use the green cuttings in your own compost heap as the sap from the branches, twigs and leaves contains toxic substances. The fruit pods containing the seeds are among the most poisonous parts of the plant. The seeds must never be eaten! A critical dose for children is considered to be as little as two seeds. [Source: GIZ Nord]

Contents: Wistarin (glycoside), similar to cytisine (poisonous substance in laburnum), but with a less strong effect (this was extracted from the bark in experiments carried out in 1887) – however, this poisonous substance is mainly found in the bark and roots. The leaves also contain a toxic resin as well as allantoic acid and lectins.

LD50 for animals: unknown

LD50 for humans: unknown; not clinically proven!

Symptoms of wisteria poisoning: The toxic substance wistarin has a nicotine-like effect on humans. In particular, it affects the spinal cord (especially the ganglia – clusters of nerve cells) and the medulla oblongata (extended medulla in the brain stem at the end of the spinal cord). These are primarily responsible for the following bodily functions Nausea, breathing and the vasomotor system (nerves responsible for blood vessels and blood pressure). As this initially leads to an excited state and later to a paralysed state, the body’s ability to regulate these functions is in most cases no longer possible without treatment.

The main symptoms are stomach problems with abdominal pain, vomiting and diarrhoea. Other signs of poisoning include dilated pupils and circulatory problems, possibly leading to circulatory collapse. The more seeds ingested, the more severe the symptoms, as a greater amount of poison is released. In severe cases of poisoning, death may occur from respiratory arrest (due to paralysis of the respiratory muscles) and circulatory arrest.

First aid: If you suspect that you have been poisoned by the plant, seek medical treatment immediately! You cannot take any measures yourself!

Other names of the wisteria: The plant is known by several other names in germany. These include “Wisterie” (derived from the botanical genus name “wisteria”) and Glyzinie.

Origin of name: The german name “Glyzinie” is derived from the ancient Greek word “γλυκύς (glykys)”. This can be translated into English as sweet – as some species of the glycine genus actually have sweet roots. Wisteria does not belong to this plant genus! See also: Further research into the origin of the genus name. The botanical genus name Wisteria was chosen in honour of the German-American physician Caspar Wistar (1761-1818) by the British botanist and zoologist Thomas Nuttall in his work: The genera of North American plants, and a catalogue of the species, to the year 1817. The German name “Blauregen” is said to have developed from the blue-coloured, hanging flower clusters.

Origin of the genus name: The botanist Carl von Linné first described the plant genus “Glycine L.” in his work Species plantarum. He also incorrectly assigned wisteria to the genus Glycine. The genus name “Glycine” was accepted by the botanist Carl Ludwig von Willdenow in his work Species Plantarum. Editio quarta 3 (2), page 1053 from 1802. The reclassification to the generic name “Wisteria” was made by the British botanist and zoologist Thomas Nuttall in his work: „The genera of North American plants, and a catalogue of the species, to the year 1817“.

It is assumed that the generic name “Wisteria” is a misspelling, as the German-American doctor was called “Caspar Wistar”. There is no proof of this. However, it seems to be a plausible theory.

Origin of the name of the chinese wisteria: It can be assumed that Linné probably already mentioned one of the two wisteria species in his work [as above]. The first reclassification of the chinese wisteria was made by the British botanist John Sims (1749 – 1831). He gave the plant the botanical name “Glycine sinesis”.

The second redescription and simultaneous reclassification to the genus Wisteria was carried out by the botanist Augustin-Pyrame de Candolle (abbreviation DC) in his work Prodromus Systematis Naturalis Regni Vegetabilis 2 on page 390 from the year 1825, in which an attempt was made to change the name of the plant from “Glycine sinesis” to “Wisteria chinesis” (source 1 / source 2). In the end, however, the name “Wisteria sinesis” (presumably a misspelling of the botanical species name) prevailed. This is recognised as the main name in the GBIF. However, the alternative spelling “Wisteria chinensis” can also be found in the synonyms. This was also suggested by other authors such as “Bunge / Sweet”.

Origin of the name of the japanese wisteria: One of the first descriptions of the japanese wisteria is by Carl Ludwig von Willdenow in his work Species Plantarum. Editio quarta 3 (2): page 1066 / year 1802. Botanist Augustin-Pyrame de Candolle (abbreviation DC) reclassified it to the genus wisteria in his work Prodromus Systematis Naturalis Regni Vegetabilis 2 on page 390 from 1825. The botanical name Wisteria floribunda is still the accepted name today [GBIF].

The other existing species of the genus Wisteria will not be discussed further here!

Distribution codes: none – only cultivations! [A, AV, M1, M2, F, K (snth.)]

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