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National Park Mystery Plant 3: It’s Toxic, and Livestock Producers Hate It

This mystery plant is pretty…… and poisonous. Sheep, cattle, pigs, and goats will eat it, and therein lies the rub.

The half-dozen poisonous varieties of this plant, all perennials, are members of the Fabaceae family. They produce pretty summer blooms that add to the beauty of the rugged Western landscapes in which they are found. You’ll find them in lots of places in the foothills, mountain ranges, and intermountain areas of the western states. That’s because they grow in a variety of open and not-so-open ecosystems, including sagebrush, grasslands, aspen groves, and coniferous forests.

You'll find our mystery plant growing in a number of western national parks, such as Great Basin National Park, Yosemite National Park, and Golden Gate National Recreation Area.

Some varieties of our mystery plant can grow up to 40 inches tall under ideal conditions, but most varieties top out at around one to two feet. The leaves of the plant are distinctive, being comprised of several leaflets radiating from a central point.

The mystery plant blooms during the warmest months, meaning June through August in most locales. The most common color of the blossoms is blue, but some varieties have white, pink, or yellow flowers. Seed pods usually make their appearance in July and August.

Ranchers and herdsmen hate this plant with a passion and may call some of their most imaginative expletives into play when discussing it. You really can’t blame them. Viewed from the perspective of the livestock producer, this plant is pure trouble.

The poisonous varieties of this plant are toxic to sheep, cattle, pigs, and goats (yes, even goats) from the time the plants begin to grow until the time the seed pods of mature plants shatter in late summer or early fall. Every part of the plant is toxic, and although younger plants are more toxic, the seeds and seed pods of older plants are more dangerous because animals find them tasty and will often eat them in preference to safe forage. Since hay contaminated with the seeds and pods of this plant can poison livestock too, animals may be at risk even when they are on supplemental feed.

The effects of the poisoning depend on the type of livestock and factors such as the amount and type of plant material ingested during a specific time interval. (If ingested repeatedly over a period of 3-4 days, even small amounts that are normally harmless may accumulate to dangerously toxic levels.) Among the classic symptoms or outcomes are:

• Nervousness
• Excessive salivation or frothing at the mouth
• Depression, lethargy, or loss of appetite
• Difficulty in breathing
• Convulsions, twitching leg muscles, or loss of all muscular control
• Coma
• Death
• Hepatic degeneration (liver damage)
• Fetuses with skeletal defects or cleft palate

There is no known treatment for the poisoning, but livestock producers know that animals not too badly poisoned may fully recover if given safe supplemental feed and allowed to rest.

Do you know what this mystery plant is? Be sure to read Mystery Plant Revealed in tomorrow's Traveler for the answer and more discussion.


Thanks, tomp. That will help. I'm familiar with the EPMT website, but like you, I'm a bit leery about using a 2004 info source without first checking for updated info. Darn it; now you've got me really interested in this topic. I was hoping to get some of this backlog chewed down before taking on another big project. :o)

I'll pitch in with results of a query of all plant species with "weedy" status in NPS units.

You might also check out the old NPS EPMT (exotic plant management teams) website:

I agree that it's an important topic. Rob. Controlling weeds (plants that are "out of place") is getting more complicated and costly all the time in our national parks. We're stretched mighty thinly here at Traveler right now, but I don't see why we couldn't work some more relevant material in as we get the chance. Thanks for the suggestion.

Bob, I sense another article in the making...weeds and our National Parks. It would probably go over well. There have been some great comments here.

Executive Director,
Crater Lake Institute
Robert Mutch Photography

The Maui County Division of Transportation imported mulch from Australia a few years ago to use on newly reseeded slopes where road construction had occurred. Unfortunately, the mulch included the seeds of a highly invasive form of fireweed. The weed grows in clumps reaching about 14 inches high and sports clusters of small yellow flowers. It is amazingly prolific and has exploded across the landscape crowding out native grasses and other pasture plants. It is also toxic to grazing animals causing liver damage, aborted fetus and other internal distress that can eventually kill affected ungulates. It is negatively affecting the island cattle industry and possibly causing problems with resident wildlife.

Thanks for the clarification and additional information, tomp. I'm obviously way out of my depth here.

Locoweed is a common name for many species of Astragalus. Astragalus species are also in the Fabaceae, also have compound leaves composed of leaflets, also occur in numerous western US NPS units, also are toxic to cattle, goats, sheep, etc.. The reason Astragalus isn't the right answer is that there are _many_ more species of Astragalus than of Lupinus: ITIS lists 39 species of Astragalus where the species name begins with the letter 'a', and over 100 total species. The flora of Utah (at least used to) list ~300 Astragalus species and subspecies.

OK, another slight difference is that most Astragalus are toxic enough (with somewhat different toxins than Lupines) to be somewhat distasteful to cattle, but cattle will eat many species of Astragalus if there's nothing better around. Lupines are tasty enough that they can be preferred over grass. [But, then again, sheep will overeat non-poisonous clover (also Fabaceae), bloat, and die.] The problem with peas (Fabaceae) in general is their soil symbiont can fix nitrogen and thus peas tend to have higher N and protein content, and thus are higher-value food for grazers and browsers. Therefore, natural selection has favored them investing more resources into toxins to prevent or at least reduce their being eaten. Non-native grazers like cows & sheep often haven't evolved to be able to "taste" those toxins, so they taste the high-protein and not the toxins and can poison themselves.]

Locoweed is also the common name for many species of Oxytropis, another legume (Fabaceae). And milkvetch is also a common name for many Astragalus species.

Larkspurs are almost always Delphinium species, in the Ranunculaceae or Ranunculus (buttercup) family, about as distantly related to Fabaceae as there is within the dicots.

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