Ponderosa Pine

April 11, 2011 Print Friendly and PDF
Ponderosa Pine (Pinus ponderosa), courtesy of Intermountain Herbarium at Utah State University

Scientific Name: Pinus ponderosa
Distribution: Throughout the Western United States, and Western Canada.
Type of Poison: Believed to be isocupressic acid
Signs of Poisoning:

  • Abortion characterized by weak parturition contractions, excessive uterine hemorrhage, and incomplete dilation of the cervix.
  • Calves may be weak and may survive if abortion is near term.
  • Persistently retained placenta
  • There may be indications of the impending abortion.


About Ponderosa Pine

Growth Characteristics: Ponderosa pine has a long, clear trunk and a high, short, open crown. It averages 42 inches in diameter and 165 feet in height at maturity.

Flowers/Inflorescence: Male and female cones are separate but found on the same tree. The male cones are small, yellowish, and in clusters. Female cones average 4 inches in length when mature. The tips of the cone scales are armed with short, sharp, outcurved prickles. The female cones, like all pines, require two growing seasons to mature.

Fruits/Seeds: Small seeds, about one-fourth inches long, with a broad terminal wing about 1 inch long.

Leaves: Needle-like, in bundles of threes, occasionally in twos. The leaves are stout, dark to yellow-green, and about 7 inches in length. The leaves remain attached and continue growing for approximately five years. Buds are resinous, reddish-brown, and about one-half inches long.

Stems: Twigs are usually coarse, stout, and orange-yellow. Bark is gray to black and scaly on young trees. As the trees reach maturity, the bark thickens to as much as 4 inches and breaks into large, flat, yellow-brown, scaly-topped plates separated by deep furrows. Old trees have a characteristic yellow bark and are locally named yellow pine. The bark has a fragrance of vanilla or butterscotch. The wood is highly desirable, light in weight, rather hard, strong, and relatively fine-grained. The branches of ponderosa pine are self-pruning.

Details of needles and cone of ponderosa pine (Pinus ponderosa), courtesy of Dr. Roger Banner, USU Extension

Where and When It Grows

Ponderosa pine grows in all of the states west of the Great Plains and in western Canada. Pine needles can be made available to cattle from slash remaining after logging operations, windfalls, or dried fallen needles. Discarded Christmas trees have been known to cause abortion in cows.

How It Affects Livestock

The needles of ponderosa pine cause abortion when grazed by cattle. The abortions occur primarily from late fall to early spring, during the last trimester of pregnancy. Pine needles are generally grazed by cattle when they are stressed, such as by snow, wind, cold, changes in feed, or hunger.

Abortions may begin within 48 hours after pine needles are ingested. Some cows abort as much as two weeks after having had access to the needles. Only a small amount of needles is required to cause an abortion. Incidence can vary from only a few to 100% of the cows involved. There are no indications of the toxicity to cattle eating the needles. The cow may deliver a live calf if she is near term at the time she eats the needles.

A persistently retained placenta is a constant finding regardless of the gestational stage of the abortion. In case of complications from the retained placenta, consult your local veterinarian.

How to Reduce Losses

To reduce losses through abortion, the most important factor is to avoid ingestion of ponderosa pine needles, especially during the third trimester. Fencing off those areas during late pregnancy might be a practical method if the area is small. Providing ample feed helps to ensure that cattle are not driven to eating pine needles because they are hungry. Also, feeding across a large area is important because some cattle are not forced out of the feeding area with nothing but pine needle areas available for foraging.

Avoid feeding hay on top of pine needles. This may cause involuntary eating of pine needles that could lead to abortion. At the present time, there are no drugs or vaccines that would be helpful in preventing pine needle abortions.


L.F. James, R.F. Keeler, A.E. Johnson, M.C. Williams, E.H. Cronin, and J.D. Olsen. Plants Poisonous to Livestock in the Western States. U.S. Department of Agriculture, Agriculture Information Bulletin 415, 90 pp. 1980.

Mass, John, DVM. Pine Needle Abortion. 1996. UCD Vet Views, California Cattleman, April 1996. University of California, Davis. 16 September 2009. http://www.vetmed.ucdavis.edu/vetext/INF-BE_cca/INF-BE_cca96/INF-BE_cca9604.html

Pratt, Mindy S. Ponderosa pine. Range Plants of Utah. 2008. Utah State University Extension Service. 16 September 2009. http://extension.usu.edu/rangeplants/htm/ponderosa-pine

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This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.