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Plants dangerous to horses

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This list summarises Australian plants that are dangerous to horses. This list is not exhaustive.

Always consult your vet if you suspect poisoning and disallow the horse from accessing the source. This applies to any type of poisoning.

Plant NamePictures of plants and major symptoms
Blue canary grass (Phalaris coerulescens)https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?
page=nswfl&lvl=gn&name=Phalaris

Alkaloid poisoning Sudden death

Cotton bushes (Gomphocarpus spp. & Asclepias spp.)https://images.ala.org.au/image/details?imageId=622e6534-2445-4258-b111-6f92f8e501f4

Cardiac glycosides poisoning.


Only a few leaves can be toxic, even dead leaves.

  • Weakness
  • Diarrhoea
  • Sweating
  • Heart failure
  • Death
Crotalaria spp.https://www.anbg.gov.au/photo/apii/genus/Crotalaria

Alkaloid poisoning

  • Depression
  • Changes in behaviour
  • Refusal to eat
  • Colics
  • Abdominal swelling
  • Possible death
Foxglove (Digitalis purpurea)https://bie.ala.org.au/species/https://id.biodiversity.org.au/node/apni/2920821

 Cardiac glycosides poisoning

Only a few leaves can be toxic, even dead leaves.
  • Weakness
  • Diarrhoea
  • Sweating
  • Heart failure
  • Death
Hemlock (Conium maculatum)https://bie.ala.org.au/species/https://id.biodiversity.org.au/node/apni/2899897#gallery
  • Muscle weakness
  • Respiratory failure
  • Death
  • Frequent urination and defecation
  • Staggering
 
Mother of Millions (Bryophyllum spp.)https://bie.ala.org.au/species/https://id.biodiversity.org.au/node/apni/2905853

Cardiac glycosides poisoning

Only a few leaves can be toxic, even dead leaves.
  • Weakness
  • Diarrhoea
  • Sweating
  • Heart failure
  • Death
Oleander (Nerium oleander)https://bie.ala.org.au/species/https://id.biodiversity.org.au/node/apni/2899812  

Cardiac glycosides poisoning

Only a few leaves can be toxic, even dead leaves.
  • Weakness
  • Diarrhoea
  • Sweating
  • Heart failure
  • Death
Paradoxa grass (Phalaris paradoxa)https://bie.ala.org.au/species/https://id.biodiversity.org.au/node/apni/2895519#gallery

Alkaloid poisoning

Sudden death
Paterson’s Curse (Echium plantagineum)https://bie.ala.org.au/species/https://id.biodiversity.org.au/node/apni/2889451#gallery

Alkaloid poisoning

  • Depression
  • Changes in behaviour
  • Refusal to eat
  • Colics
  • Abdominal swelling
  • Possible death
Prunus spp: this includes all prunus trees such as apricot, cherry, almond, plum, peach trees etc. Leaves are lethal, even dead onesCyanide poisoning. Can occur within 10 minutes of eating the leaves.  
  • Red mucous membranes
  • Rapid breathing
  • Convulsions
  • Coma
  • Death
Rubber vine (Cryptostegia grandiflora) and Purple rubber vine (Cryptostegia madagascariensis)https://bie.ala.org.au/species/https://id.biodiversity.org.au/node/apni/2889657#overview

Cardiac glycosides poisoning

Only a few leaves can be toxic, even dead leaves.
  • Weakness
  • Diarrhoea
  • Sweating
  • Heart failure
  • Death
Swainsona spp.https://bie.ala.org.au/image-search/https%3A//id.biodiversity.org.au/node/apni/7247017

  • Weakness
  • Depression
  • Convulsions
  • Death
 
Two & One leaf cape tulips (Moraea miniata & Moraea flacida – also known as homeria falcida and homeria miniata)https://www.anbg.gov.au/photo/apii/id/a/12204
https://bie.ala.org.au/species/https://id.biodiversity.org.au/node/apni/2901268

Cardiac glycosides poisoning Only a few leaves can be toxic, even dead leaves.

  • Weakness
  • Diarrhoea
  • Sweating
  • Heart failure
  • Death
Yellow Oleander (Cascabela thevetia)https://weeds.brisbane.qld.gov.au/weeds/yellow-oleander

Cardiac glycosides poisoning

Only a few leaves can be toxic, even dead leaves.
  • Weakness
  • Diarrhoea
  • Sweating
  • Heart failure
  • Death
Ornithogalums (Ornithogalum spp.) https://bie.ala.org.au/species/https://id.biodiversity.org.au/node/apni/2903443

Cardiac glycosides poisoning Only a few leaves can be toxic, even dead leaves.

  • Weakness
  • Diarrhoea
  • Sweating
  • Heart failure
  • Death
Blue periwinkle (Vinca major)https://bie.ala.org.au/species/https://id.biodiversity.org.au/node/apni/2908818

Cardiac glycosides poisoning

Only a few leaves can be toxic, even dead leaves.
  • Weakness
  • Diarrhoea
  • Sweating
  • Heart failure
  • Death
Pheasant’s eye (Adonis microcarpa) https://en.wikipedia.org/wiki/Adonis_annua

Cardiac glycosides poisoning

Only a few leaves can be toxic, even dead leaves.
  • Weakness
  • Diarrhoea
  • Sweating
  • Heart failure
  • Death
Black locust (Robinia pseudoacacia)https://bie.ala.org.au/species/https://id.biodiversity.org.au/node/apni/2909491

Lectins poisoning

  • Colic
  • Diarrhoea
  • Dilated pupils
  • Irregular heart beat
  • Possible death
Crofton weed & Mistflower (Ageratina adenophora or Eupatorium adenophorum & Ageratina riparia or Eupatorium riparium)https://bie.ala.org.au/species/https://id.biodiversity.org.au/node/apni/2916475

Respiratory illness

  • Respiratory failure may occur during exercise
  • Depression
  • Weight loss
  • Can cause permanent lung damage
  • Death
Hardheads, Knapweed (Acroptilon repens, Centaurea repens)https://weeds.dpi.nsw.gov.au/Weeds/CreepingKnapweed
https://agriculture.vic.gov.au/biosecurity/weeds/priority-weeds/hardheads

Sudden symptoms but the illness develops after a long period of exposure

  • Inability to drink or eat
  • Dehydration
  • Irreversible brain damage
  • Death by starvation and dehydration
 
St Barnaby’s Thistle (Centaurea solstitialis)https://bie.ala.org.au/species/https://id.biodiversity.org.au/node/apni/2895079

Sudden symptoms but the illness develops after a long period of exposure

  • Inability to drink or eat
  • Dehydration
  • Irreversible brain damage
  • Death by starvation and dehydration
Blue Green Algaehttps://www.csiro.au/en/research/natural-environment/ecosystems/blue-green-algae/what-are-blue-green-algae  
  • Sudden death from cyanide poisoning
  • Photosensitisation (sunburn lesions) on non-pigmented skin
  • Muscle tremors
  • Diarrhoea and blood in the droppings
  • Liver damage
 
Red maple (Acer rubrum [Aceraceae])

 https://en.wikipedia.org/wiki/Acer_rubrum

  • Feed refusal
  • Red-brown urine
  • Jaundice
  • Weakness
  • Coma and death
Birdsville indigo, Creeping indigo (Indigofera linnaei, Indigofera spicata)https://bie.ala.org.au/species/https://id.biodiversity.org.au/node/apni/2886993

Symptoms appear after around 10 days of eating the plants
  • Loss of appetite
  • Depression
  • Dragging of hind legs
  • Paralysis of back legs
  • Death
 
Gympie Stinger, Gympi Gympi, Mulberry-leaved Stinger (Dendrocnide moroides)https://bie.ala.org.au/image-search/https%3A//id.biodiversity.org.au/taxon/apni/51249795

The pain is so intense that affected horses enter into a hysteric state and die from self-destruction and self-harming

  References:

  • Janusz Talalaj “Poisonous Plants in Australia” Echidna Press 2008
  • Mellisa Offord “Plants Poisonous to Horses, An Australian Field Guide” RIRDC 2006

14 thoughts on “Plants dangerous to horses”

      1. Hi, my neighbour claims the leaves from my trees are blowing into her very small paddocks which have no feed in them, and that her 2 ponies are eating them, and that one of them went down the other day and she claims her vet told her they are poisonous. The ponies are eating the leaves as she has no feed in the paddocks. My horse is due to come to my property in 2 weeks, so I want to know if this is true as i don’t want to risk her getting sick. My vet cant find any information regarding them being poisonous.

        1. I cannot find any information either stating they are poisonous to horses or any other livestock. However, if the ponies are starving, they will eat anything, not just those, and they will eat as much as they can. What else does she have in her paddock? and if the ponies are starving, they might also have colic which is highly possible as they might be eating dirt.
          Maybe ask her a written letter from her vet stating this is poisonous and what sort of poison it emits, and even ask the letter to state this is what has caused the horse to be ill. If the vet does not want to do this, then I highly doubt the tree is the cause of illness. Of course, if you want to stay on good terms with your neighbour, then you might need to trim your tree.
          Horses who are not starved don’t normally eat rubbish.
          This assessment of the tree also states there is no evidence that it is toxic to animals: https://www.hear.org/Pier/wra/pacific/eucalyptus_torelliana_htmlwra.htm

          1. I agree with you. She thinks she is saving these poor ponies from the knackers, and i dont think she feeds them enough. Their paddocks are tiny with barely any grass. She really knows nothing about horses as all. I would also say they are eating the leaves that blow in as they are not being fed enough. My vet cant find any info either nor can I. I might try to talk to her vet. Thank you for your help πŸ™‚ Is there any government department that you know of that I could write to??

          2. Depending in which state you are, you can contact the Department of Agriculture and Fisheries (QLD – maybe called DPI in other states?) and ask them about the tree, or even a university, rangers etc.
            As for the ponies, if they are not cared for accordingly, then you should call the RSPCA so they can be assessed. The officers can also explain to the lady what to do and not do. I hope this helps πŸ™‚

    1. Hi there,
      I don’t think so but there are so many species of Stachytarpheta. The Stachytarpheta jamaicensis is not poisonous as far as I know (it’s the light blue one).
      Hope this helps

    1. Hi there,
      I don’t believe they are but you would need to check all the different varieties to be sure. Unless a horse is starving, they don’t usually eat plants poisonous to them. Just keep an eye on the horse to see what he eats and remove the danger as much as possible, feed the horse adequately with hay/forage. Hope this helps, Cass

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