Article 41 – ‘Toxicity’ 6.
Hi welcome to Taiga Bonzai, we continue our journey through the alphabet discussing the toxicity of trees and shrubs, some of which are used in bonsai horticulture.
Introduction – some of the species mentioned here are endemic to tropical and sub-tropical regions, others are found in the northern hemisphere.
Umbrella tree – Schefflera arboricola. (syn. Heptapleurum arboricolum) also a member of the Araliaceae family is native to Taiwan, but can be found world-wide as a house plant and also in bonsai. S. arboricola should not be mistaken for S. actinophylla, because of the height difference.
Moreover, S. arboricola has different leaf colour and patterns, some variegated with cream to white flowers with yellow edges or centres. Although much depends on the individual cultivar. S. arboricola is poisonous and carries the same toxins as S. actinophylla. Leaf consumption can cause mouth tingling and numbness, vomiting and abdominal pain and sap when in contact with skin can cause irritation and rash.

Viburnum – Lantana. family Adoxaceae. Also known as the ‘wayfaring tree’ is a deciduous shrub native to Europe, but can be found in Asia and northern Africa and is a relatively common specimen in bonsai.
It’s oval dark green leaves have a downy or hair like covering on the underside and flowers that are creamy white in colour and green fruit. These ripen to a bright red eventually turning black when mature. The berries if consumed although mildly toxic can cause vomiting, diarrhoea and abdominal pain if ingested in large quantities.
Viburnum – Opulus. family Adoxaceae. Is often referred to by its common name the ‘Guelder rose’ and is native to Europe, northern Africa and central Asia. This deciduous shrub has three lobed leaves that are opposite to each other having an appearance similar to maples.
The flowers in clusters are white in colour with their centre being fertile surrounded by an infertile ring that are produced in early summer; the fruit that is bright red. The berries if consumed although mildly toxic can cause vomiting, diarrhoea and abdominal pain if ingested in large quantities.

Virginia creeper – Parthenocissus quinquefolia. family Vitaceae. Is native to north America, Canada, Mexico, Guatemala and Europe. It is a prolific deciduous climbing vine reaching heights of over 30m. (100ft) It attaches itself to smooth surfaces by small adhesive pads.
This plant normally seen growing on the sides of buildings has striking colours throughout the seasons. The leaves change from various greens to yellow to orange to red and purple and this colour change makes the species attractive to bonsai.
The flowers are small and greenish white in colour, which change into purple/black berries in the autumn. The sap, leaves and berries are poisonous because they contain the toxin oxalic acid. Prolonged skin contact can be dangerous and ingesting any part even small amounts can cause kidney damage and death to humans.
White cedar – Spp. family Cupressaceae. Include Chamaecyparis thyoides – Atlantic white cypress, Cupressus lusitanica – Mexican white cedar, Thuja occidentalis – Northern white cedar, Thuja plicata – western red cedar and Cryptomeria japonica – Japanese cedar. Cedars are conifers and are found in many parts of the world, from northern climes to temperate zones.
They have many uses for example, grown as barriers, wind breaks, dense hedging in parks and gardens and are a common species in bonsai. However, all cedars carry toxins the primary irritant being plicatic acid and some are more potent than others for example.
The western red cedar and Japanese cedar have the highest content of plicatic acid and exposure to it can cause severe asthma, rhinitis or conjunctivitis, that can be progressive. In addition, plicatic acid in contact with skin can cause a hypersensitivity reaction, a type of response seen in tuberculin skin tests.

Willow – Salix alba. family Salicaceae. Is a species native to Europe, but is also found in western and central Asia. Within this genus are: Salix alba Vitellina – a willow with yellow shoots and Salix alba var. Britzensis, Cardinal and Chermesina having orange to red shoots.
The willow a medium sized deciduous tree can be in a weeping form or with a dome shaped crown with long thin leaves pointed at the end. (5–10cm long x 0.5–1.5cm wide) It is often found in bonsai in designs that include slanting (Shakan) and (Fukinagashi) wind swept.
Male and female trees each produce their own flowers in the form of catkins that appear in the spring and when mature are wind pollinated. However, the willow contains salicylate toxins in the bark that if ingested can cause the following. Ulcers, nausea, vomiting, stomach bleeding, kidney inflammation, tinnitus and skin rash.
Wisteria – Spp. family Fabaceae. Includes various species of climbing vines. (Plants that climb by their shoots) Wisteria brachybotrys, Wisteria brevidentata, Wisteria floribunda, Wisteria frutescens, Wisteria macrostachya, Wisteria sinesis, Wisteria venusta and Wisteria villosa.
These Wisteria types are predominantly native to the eastern north America, China, Japan and Korea. Although these species are found in bonsai, arguably the most common is the Wisteria sinesis that when in bloom has a striking floral display for example.
The great wisteria at the Ashikaga flower park in Tochigi, Japan, which covers more than 1,990 square meters over half an acre. Wisteria flowers are between 10 to 80cm in length and produced in pendulous racemes and are either purple, violet, pink or white.
All parts of the wisteria are poisonous, they contain the toxin saponin and if ingested the symptoms are: nausea, vomiting, abdominal pain, diarrhoea, severe gastroenteritis, dizziness, confusion, speech problems and collapse.

In the next article on ‘Toxicity’ we conclude our journey through the alphabet with ‘X’, ‘Y’ and ‘Z’. Until next time, BW, Nik.

