Toxic Plants
Animal owners and livestock managers work hard to ensure the health and safety of their animals by providing high quality feed, forage, or hay for good nutrition and performance. Weeds in natural areas can pose risks to animal health, especially to grazing species.
Providing proper feed and grazing combined with identification and control of poisonous plants in natural areas and pastures—and sometimes your own landscaping—can prevent poisoning of the animals you care for.
Toxicity & Animals
Plants produce toxins as a defense against grazing— which means that toxic plants usually smell or taste bad. Animals generally do not want to eat them.
Young animals sometimes eat these plants out of curiosity, but even older animals will graze on these undesirable plants:
- When desired forage is scarce.
- When owners give them bad food or forage that contains poisonous plants.
Most poisonous plants will not kill an animal. Instead, animals will suffer from chronic toxicity—repeated exposure over time. The common symptom seen in this type of poisoning is wasting (poor growth and low weight).
There are plants, however, that will cause acute toxicity—one time, damaging exposure. The animal will usually die soon after eating the plant. Luckily this poisoning is rare.
Common Poisonous Plants
Many of the following plants are commonly seen in the landscape. For photos and identification tips, visit the Center for Aquatic and Invasive Plants database or view the presentation "Poisonous Plants in Pastures."
If you are ever unsure of your identification of pasture plants, you can always have the plant specimen confirmed by your county's Extension agent.
Azaleas
All parts are toxic. The toxins affect the stomach and intestines. Symptoms include nausea, weakness, salivating. Death is rare.
Bracken Fern
All parts are toxic, particularly the roots. In horses, the toxin causes vitamin B1 deficiency, seen through high fever and lack of coordination. In cows, the fern causes hemorrhaging with swelling and bloody waste as symptoms. Sheep and goats are less susceptible.
Poisoning usually occurs over multiple exposures, not all at once. Animals usually eat bracken fern during the summer when they seek out shaded environments.
Cherry (Prunus sp.)
There are many different species of cherry and all are toxic. These plants are common around pastures since the seeds are easily spread by birds. Cherry produces cyanide in the leaves.
Cherry, Black
All parts are extremely toxic, but wilted leaves are the most. The tree contains cyanide, and all animals are susceptible, especially ruminants. Symptoms included staggering or convulsions within fifteen to thirty minutes of ingestion; death within one hour.
Coffee Senna
All parts are toxic, but mainly the seeds. Wasting or dark brown urine are symptoms of poisoning; large quantities must be ingested for symptoms to appear. Poisoning is most common in the fall after frost since coffee senna will remain green after bahiagrass and bermudagrass go dormant.
Crotalaria (Rattlebox)
The whole plant is poisonous, the seeds in particular. Weakness, confusion, and jaundice from liver damage can occur. Animals may die months after eating crotalaria.
Hemlock
Has a high toxicity. Often found along fences lines and stables.
Lantana
This ornamental is often grown in Florida gardens, but has also escaped into natural areas. It can be found along fencerows and tree lines.
The whole plant is toxic. Large quantities cause acute toxicity, while smaller amounts cause mouth sores and skin cracking.
Nightshade
The berries are the main poisonous part of this plant, the leaves less so. Green berries are particularly toxic. Symptoms include acute toxicity, progressive unthriftiness (failure to put on weight), and gastric distress.
Nightshade is unpalatable; animals will rarely eat enough to cause death.
Perilla Mint
The whole plant, and especially the flowers, is toxic. Poisoning incidents are more common in the fall when the plant is flowering. Poisoning symptoms include labored breathing.
Perilla is usually found in shady areas around forest edges and farm buildings. It can be recognized from its mint-like odor.
Red Maple
Red maple can cause a blood disorder that leaves an animal sick for an extended period. Like cherry, wilted leaves are the most toxic.
Others
Other plants involved in reported poisonings or deaths of pets and livestock (including sheep and goats, poultry, rabbits, dogs, cats, cattle, and horses):
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Poisoning Symptoms
Sometimes poisoning may not be immediately obvious, especially if you have not witnessed an animal grazing on a toxic plant. If you think your animal has been poisoned, look for the following symptoms:
- Standing alone
- Acting disoriented
- Holding head down
- Refusing feed
- Drinking large amounts of water
- Wasting
- Shaggy coat
Contact your local Extension agent and veterinarian if you suspect your animal is poisoned.
Providing good grazing and food sources and having suitable fencing are the best ways to protect livestock and animals from toxic plants. Mowing weeds is also helpful, especially in the fall.
Remember that poisonous plants are not safe in hay—many toxic compounds do not break down during curing. If you use weedy hay, make sure you know what weeds are present.
For more questions about forage management, animal and livestock health, plant identification, and more, contact your local Extension agent.
Adapted and excerpted from:
J. Ferrell, "Poisonous Plants in Pastures," UF/IFAS Weed Extension (accessed 06/2011).
D. Mudge, "Toxic Plants: Recent Farm Animal Poisonings" (650KB pdf), UF/IFAS Central Florida Livestock Agents’ Group (accessed 06/2011).
J. Ferrell, "Poisonous Plants--Are Your Animals at Risk?" (164KB pdf), Presentation, 2011 Florida Beef Cattle Short Course (accessed 06/2011).
Related Sites & Articles
- UF/IFAS Publications
- Toxicity to Poultry of Common Weed Seeds
- Weed Management in Pastures
- UF/IFAS Sites
- Weed Management Recommendations
- Other Sites & Publications
- Plants Poisonous to Livestock and Other Animals--Cornell University
