GARDENING: The toxic plants hiding in CQ gardens and homes

Around Central Queensland, you may find some plants in your garden with varying degrees of toxicity.

This week I was contacted by gardener in Gracemere who after cutting out a Cook Tree or Thevetia peruviana found the top of his hands had blisters.

He did not realise that the Thevetia was a poisonous plant.

In this case the gardener had not used gloves and his hands become covered in the milky sap of the Cook Tree.

If you are pruning any of these plants, you should wear protective gloves and goggles, and make sure you quickly dispose of the lopped branches.

Do not put hands to mouth or eyes while working, and make it a ritual to wash away any residue are handling.

You should really follow these rules with every plant, poisonous or not, because strong weedicides, insecticides, fungicides and herbicides are probably a greater risk to gardeners that any of the plants that I have listed.

Clean hands also reduce the risk of spreading bacteria from one plant to another.

Some plants have been grown in gardens for many years, others have been used in landscapes because of the plants water-wise qualities.

I would not suggest that you exclude these plants, however, knowing which plants are poisonous will help parents educate their children not to play with the fruits or flowers.

This is very important when it comes to little children, who are prone to feeling everything with their mouth.

Fortunately, most poisonous plants have their own way of deterring curiosity, such as thorns or an unpleasant odour, but it is still wise to be aware of some of these plants.

Below, I have listed some of the more common poisonous plants that you may find growing around this area.

Acokanthera oblongifolia Flowers Fruit
Acokanthera oblongifolia Flowers Fruit

Acokanthera oblongifolia or Wintersweet - can quite often be found in gardens where birds have deposited the seeds, resulting in many gardeners growing this plant without realising.

With milky sap and sweet smelling, pure white flowers, it is an attractive addition to the garden.

It can grow to a height of 3m, and following flowering, it has dark blue, plum-like fruit.

If you were to eat the leaves, fruit or bark of this plant, it will cause a gastro-intestinal irritation and have a digitalis-like effect on the heart.

The sap can also cause irritation to the eyes, skin or throat. Toxicity category 2 & 3.

Brugmansia candida
Brugmansia candida

Brugmansia candida or Angels Trumpets - is a South American native widely grown throughout tropical Australia.

It produces a spectacular display of large white trumpet-shaped flowers, and has showy tropical green foliage.

It is hard to believe that this 3m high plant is so poisonous.

There are many cases of poisoning from this plant reported each year, mainly by children who eat the seeds or parts of the flower.

It should also be noted that the stems and leaves are also quite poisonous.

Symptoms include a dry mouth, difficulty in speech and swallowing, vomiting, diarrhoea, fever, confusion, delirium and even a tendency to violence. There have been several cases where those who have eaten some of this plant have died. Toxicity category 1,3 & 4.

Castanospermum australe flower
Castanospermum australe flower

Castanospermum australe or Black Bean - is a beautiful native shade tree that has been grown in home backyards and public parks for over 100 years.

The tree produces large, orange and red, pea-flower shaped, flowers in clusters along the trees branches.

After flowering large, heavy, rounded seed pods are formed and if eaten, these seeds can cause severe diarrhoea, vomiting, abdominal pain and dizziness.

The sawdust of this tree can cause dermatitis, eczema and nasal irritation. Toxicity category 2,3 & 4.

Dieffenbachia Camille picture by Cellar Door Plants
Dieffenbachia Camille picture by Cellar Door Plants

Dieffenbachia species or Dumbcane - is a decorative ornamental shrub, usually grown as an indoor plant.

In the garden it may reach a height of over 2m.

Chewing or biting the stem of the large fleshy leaves can cause a large amount of salivation and an intense irritation and burning in the mouth, lips and tongue, resulting in eventual speechlessness, hence the common name of dumbcane.

These effects may last for several days. Toxicity category 2 & 3.

Euphorbia tirucalli picture by Boething Treeland Farms
Euphorbia tirucalli picture by Boething Treeland Farms

Euphorbia tirucalli or Naked Lady - is probably one of the most widely found poisonous ornamentals in our local gardens.

It originates from Africa, and grows to around 4m in height.

The milky sap causes temporary blindness if it comes in contact with the eyes, and will also blister tender skin.

Water will not remove the sap, so alcohol (methylated spirits) is recommended to remove the sap from your hands. Toxicity category 1 & 3.

Jatropha podagrica
Jatropha podagrica

Jatropha podagrica or Coral Bush or Physic Nut or Guatemala Rhubarb - is a succulent shrub, native to tropical America, growing to around 1m tall.

It is commonly grown as a pot plant or in rockeries.

The seeds can cause vomiting and diarrhoea if eaten, and also depression and collapse, particularly in children. Toxicity category 2 & 3.

Ricinus Castor oil Plant
Ricinus Castor oil Plant

Ricinus communis or Castor Oil Plant - is another introduced species that commonly grows as a weedy shrub, often in neglected, disturbed areas such as old rubbish tips and filled creek banks.

If the seeds are eaten, severe purging, vomiting, abdominal cramping, delirium, and even death can occur. Toxicity category 1,3 & 4.

Synanenium grantii
Synanenium grantii

Synanenium grantii or African Milk Bush - is a showy small shrub is another plant that is distributed among gardens by birds.

Native to tropical Africa, it can be found in many gardens in our region.

The milky sap, produced in abundance, can cause irritation to the eyes, mouth and sensitive skin, and can sometimes cause convulsions if eaten. Toxicity category 2 & 3.

Shinus terebinthifolia
Shinus terebinthifolia

Shinus terebinthifolia or Pepper Tree - is a fast-growing shade tree that will tolerate even the driest of conditions.

For many years it was widely used and recommended by the nursery industry as a plant even a brown-thumbed gardener could have success with.

It should be noted that the red berries produced by this tree are poisonous. If berries are eaten they may cause vomiting and diarrhoea.

The sap may cause dermatitis and eye irritation.

When flowering, the tree may cause sneezing, asthma-like reactions and headache. Toxicity category: 2, 3, 4.

Thevetia peruviana
Thevetia peruviana

Thevetia peruviana or Yellow Oleander or Cook Tree - is a tropical shrub with long, narrow, shiny leaves and yellow flowers.

This plant contains large amounts of milky sap.

If eaten, virtually any part is toxic, and often fatal, to humans and animals.

Children should not be allowed to play with the attractive fruits or seeds. One seed is sufficient to kill a small child.

Symptoms can include burning in the mouth, vomiting, diarrhoea, drowsiness, dilated pupils and slow irregular pulse. Toxicity category 2 & 4.


Queensland Health has produced an easy to understand symbol for each poison category.

I would like to see the state government require these symbols to be attached to plant labels on plants sold in Queensland.

Most nursery staff have the plant knowledge to advice gardeners on whether a plant has poisonous traits, but more than half the plants sold in Queensland are not sold in nurseries.

Category 1: Extremely toxic, has been known to cause injury, permanent disability, and in some cases, death. Do not plant. Removal and disposal of existing plants is strongly recommended.

Category 2: Potentially toxic, depending on the level of exposure. Should not be grown in preschools, playgrounds, child care settings, and access should be restricted in homes with toddlers or young children (including homes where young children may visit, ie grandparents). Exclusion (such as fencing) from children’s play areas is recommended. Parents and carers should supervise carefully.

Category 3: Irritant to skin or eyes from sap, prickles, spines or stinging hairs. Keep out of reach of toddlers and children. (Many common prickly or spiny plants now have non-spiny varieties available)

Category 4: Pollen or perfume from this plant can cause respiratory problems. Not an asthma friendly plant. Do you support the idea of having poisonous plant symbols on all plant labels


One of the most informative booklets produced about poisonous plants, Plants and Fungi Poisonous to People in Queensland and was jointly produced by Queensland Health and the Queensland Environmental Protection Agency.

The booklet contains descriptions and photos of many plants that can be growing in home gardens, waterways or public parks that can be poisonous to people.

As well as listing the plants and their relative poisonous causes, it also lists basic first aid for plant poisonings. You can visit the Queensland Government Publications site and search under “Poisonous Plants” to order the booklet.

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