Most horses owners are unaware of many of the plants in Australia that are poisonous or toxic to horses.
The number of plants that are potentially harmful to horses number in the thousands. Most toxic plants are not attractive, nor palatable, to horses however there are always horses that are curious or, if feed is low, the plants become a more attractive proposition. In many cases horse only need to consume a very small amount of leaves and/or fruit to cause poisoning, in other cases the toxins are built up over a period of time.
The following is just a very small portion of some of the toxic plants currently found in Australia:
The Prunus group of plants are commonly grown in Australia and include: apricots, cherries, peaches, plums, almonds and nectarines. Poisoning in horses can be caused by swallowing just a small amount of leaves.
(also known as Salvation Jane, Lady Campbell weed, Purple bugloss, Riverina bluebell)
Paterson's Curse has been declared a noxious weeds in most States is Australia. It is found in many Australian pastures and is native to the Mediterranean region. The plant is usually unpalatable but horses will eat it if there is little other forage available. All parts of the plant are toxic to horses and the plant remains toxic even when dried.
Green potato peelings are the most toxic part of the potato plant, however all parts of the plant are toxic. Potatoes have been reported to have caused fatal poisoning in a horse after it ate old potatoes that had been composted in it's paddock.
Tomatoes are another common household plant that is toxic to horses. The leaves of the tomato plant as well as unripe tomatoes are potentially poisonous to horses, so care also needs to be taken when disposing of these plants, as well as the fruit. Care also needs to be taken to ensure tomato plants do not grow in horses' paddocks.
All parts of avocado trees are poisonous to horses but the leaves (whether fresh or dried) are the most toxic.
The oleander is a common plant that is widely grown in all parts of Australia. All species of oleander plants are highly toxic to horses, as well as to other animal species and humans. All parts of the oleander plant are toxic, including fresh and dried leaves, flowers and branches.
The bark and leaves (including dried or wilted leaves) are toxic to horses and can cause life threatening anaemia if the horse ingests even a small amount of wilted or dried leaves.
There are many species of nightshades in Australia, all with varying levels of toxicity to horses. The toxic effect of these plants depends on the species and, also what part of the plant has been ingested.
This is just a small list of some of the many poisonous plants in Australia. Mellisa Offord has written an excellent book for the Australian Government (Rural Industries Research and Development Corporation) titled "Plants Poisonous to Horses - An Australian Field Guide" which can be found on the Queensland Horse Council's Website - www.qldhorsecouncil.com