Pine (Pinus spp.) is a huge genus of evergreen trees that vary widely in size and form. Most are able to tolerate severe growing conditions, including drought, harsh winds and poor soil. The needles of many pine trees are toxic and may be dangerous, particularly to cattle and other livestock. Some plants tagged as pines, including Norfolk Island pine (Araucaria heterophylla) and Yew pine (Podocarpus macrophyllus), are not true pines, but both contain toxic compounds and should be planted with care.
The needles of at least 20 familiar pine trees are toxic and present serious risk to livestock. Although the needles, as well as the bark and branch tips, are toxic to horses, goats and sheep, cattle are especially susceptible to potentially lethal reactions, including premature births and miscarriages. Pine trees that present danger to livestock include Ponderosa pine (Pinus ponderosa), which grows in U.S. Department of Agriculture plant hardiness zones 3 through 7, lodgepole pine (Pinus contorta v. latifolia), hardy in USDA zones 4 through 8; and Monterey pine (Pinus radiata), hardy in USDA zones 7 through 10. Although some cattle are more resistant, others may abort unborn calves within two weeks after eating very small amounts. Cattle that eat large amounts of pine needles may also develop neurological or renal disease.
Miscarriage, low birth weight and other similar toxic reactions may occur in human and domestic animals after eating pine needles. However, the risk may not be as severe and life-threatening as it is for cattle and other livestock, according to George E. Burrows and Ronald J. Tyrl, authors of Toxic Plants of North America. Although people often enjoy pine needle tea with no ill effect, pine needles are not recommended for use by humans and pets.
Norfolk Island pine, also known as Australian pine, is an evergreen plant most often grown indoors; however, the plant is suitable for growing outdoors in USDA plant hardiness zones 9 through 11. The plant may cause vomiting and depression when ingested by cats and dogs, according to the ASPCA's Animal Poison Control Center. Norfolk Island pine is believed to be safe for humans; however, some people may experience skin irritation after handling the plant.
Yew pine also known as Buddhist pine or Japanese yew, is an attractive garden plant, favored for its bright green leaves and easy growth habits. However, the fleshy seeds of the yew pine, which isn't a true pine, resemble fruit and are mildly toxic when eaten by children. Symptoms of ingestion include nausea, vomiting and diarrhea. Ingestion of yew pine may also cause vomiting and diarrhea in domestic animals, including dogs, cats and horses. Yew pine grows in USDA planting zones 7 through 10.
- United States Department of Agriculture Agricultural Research Service: Ponderosa Pine (Pinus Ponderosa)
- North Carolina State University Extension: Podocarpus Macrophyllus, Podocarpus spp.
- Toxic Plants of North America; George E. Burrows, Ronald J. Tyrl
- Lippincott's Manual of Toxicology; Joshua J. Lynch, Editor
M.H. Dyer began her writing career as a staff writer at a community newspaper and is now a full-time commercial writer. She writes about a variety of topics, with a focus on sustainable, pesticide- and herbicide-free gardening. She is an Oregon State University Master Gardener and Master Naturalist and holds a Master of Fine Arts in creative nonfiction writing.