toxic plants

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Poisonous Plants: Buttercups

Hold a buttercup flower under your chin. If your chin glows yellow, you love butter. That is according to a classic childhood game anyway. Recent research explored the cellular structure of buttercup petals and revealed the anatomical reason behind their yellow glow. Apart from helping to warm the flower’s sex organs, this glow is thought to draw in pollinating insects to ensure proper pollination.

Now take the fresh green leaves of buttercups, crush them up, and rub them against your skin. On second thought, DON’T DO THAT! This is not a childhood game and should absolutely be avoided…unless, of course, you derive some sort of pleasure from painful blisters.

Buttercups, also commonly known as crowfoots, are in the genus Ranunculus and the family Ranunculaceae. Ranunculus consists of a few hundred species and is a common group of annual and perennial herbaceous plants with alternately arranged, palmately veined leaves that are either entire, lobed, or finely divided. Buttercup flowers are usually yellow (sometimes white) with 5 petals (sometimes 3 or 7) that are either borne singly or in loose clusters. The flowers are complete, having both male and female reproductive structures that are easily identifiable. Flowering usually occurs in the spring.

bulbous buttercup (Ranunculus bulbosus) – photo credit: wikimedia commons

Ranunculus species are found throughout the world. Common habitats include moist woods, meadows, open fields, wetlands and other riparian areas, as well as drier sites like roadsides and neglected, urban lots. Several species are commonly grown as ornamentals, and others are common weeds in natural areas, urban landscapes, and agricultural fields.

All buttercups contain a compound called ranunculin. When the leaves are crushed or bruised, ranunculin breaks down to form an acrid, toxic oil called protoanemonin. Contact with this oil causes dermatitis. Symptoms occur within an hour of contact and include burning and itching along with rashes and blisters. When the leaves are chewed, blisters can form on the lips and face. If swallowed, severe gastrointestinal irritation can follow, accompanied by dizziness, spasms, and paralysis. The toxic oil is also irritating to the eyes.

Ranunculus species vary in their levels of this toxic compound, and individual plants are said to be more toxic in the spring when they are actively growing and flowering. Protoanemonin breaks down further into an innocuous compound called anemonin, so dead and dried out plants are generally safe. Commonly encountered (and particularly toxic) species in North America include tall buttercup (R. acris), cursed buttercup (R. sceleratus), creeping buttercup (R. repens), littleleaf buttercup (R. arbortivus), and sagebrush buttercup (R. glaberrimus). Bulbous buttercup (R. bulbosus) has bulbous roots that are toxic when fresh but are said to be edible after they are well boiled or completely dried.

cursed buttercup (Ranunculus sceleratus)

The toxicity of Ranunculus species seems to be more of an issue for livestock than for humans. Grazing animals tend to avoid it since it tastes so bad. Those that do eat it exhibit responses similar to humans – blistering around the mouth, gastrointestinal issues, etc. In The Book of Field and Roadside, John Eastman writes about Ranunculus acris: “Cattle usually avoid the plant – its acrid juices can blister their mouths – though they can also develop something like an addiction to it, consuming it until it kills them.” Buttercups becoming dominant in pastures and rangelands is often a sign of overgrazing.

Despite – and likely due to – their toxicity, buttercups have a long history of medicinal uses. Civilizations in many parts of the world have used the leaves and roots of the plant to treat numerous ailments including rheumatism, arthritis, cuts, bruises, and even hemorrhoids. A report published in 2011 describes three patients in Turkey that had applied poultices of corn buttercup (R. arvensis) to parts of their body to treat rheumatism. The patients were treated for chemical burns caused by the applications. The report concludes by advising against treatments “whose therapeutic effects have not been proven yet by scientific studies.”

In The North American Guide to Common Poisonous Plants and Mushrooms, buttercups are listed among plant species that are skin and eye irritants, honey poisons, and milk poisons (see Appendices 3, 4, and 5). Other genera in the buttercup family may also contain high levels of protoanemonin, including popular ornamentals like Clematis, Helleborus, Anemone, and Pulsatilla. Thus, the moral of this story: handle these plants with care.

sagebrush buttercup (Ranunculus glaberrimus)

More Poisonous Plant Posts on Awkward Botany:

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Poisonous Plants: Castor Bean

A series of posts about poisonous plants should not get too far along without discussing what may be the most poisonous plant in the world – one involved in high and low profile murders and attempted murders, used in suicides and attempted suicides, a cause of numerous accidental deaths and near deaths, developed for use in biological warfare by a number of countries (including the United States), and used in bioterrorism attacks (both historically and presently). Certainly, a plant with a reputation like that is under tight control, right? Not so. Rather, it is widely cultivated and distributed far beyond its native range – grown intentionally and used in the production of a plethora of products. In fact, products derived from this plant may be sitting on a shelf in your house right now.

Ricinus communis, known commonly as castor bean or castor oil plant, is a perennial shrub or small tree in the spurge family (Euphorbiaceae) and the only species in its genus. It is native to eastern Africa and parts of western Asia but has since been spread throughout the world. It has naturalized in tropical and subtropical areas such as Hawaii, southern California, Texas, Florida, and the Atlantic Coast. It is not cold hardy, but is commonly grown as an ornamental annual in cold climates. It is also grown agriculturally in many countries, with India, China, and Mozambique among the top producers.

Silver maple leaf nestled in the center of a castor bean leaf.

Silver maple leaf nestled in the center of a castor bean leaf.

Castor bean has large palmately lobed leaves with margins that are sharply toothed. Leaves are deep green (sometimes tinged with reds or purples) with a red or purple petiole and can reach up to 80 centimeters (more than 30 inches) across. Castor bean can reach a height of 4 meters (more than 12 feet) in a year; in areas where it is a perennial, it can get much taller. Flowers appear in clusters on a large, terminal spike, with male flowers at the bottom and female flowers at the top. All flowers are without petals. Male flowers are yellow-green with cream-colored or yellow stamens. Female flowers have dark red styles and stigmas. The flowers are primarily wind pollinated and occasionally insect pollinated. The fruits are round, spiky capsules that start out green often with a red-purple tinge and mature to a brown color, at which point they dehisce and eject three seeds each. The seeds are large, glossy, bean-like, and black, brown, white, or often a mottled mixture. They have the appearance of an engorged tick. There is a small bump called a caruncle at one end of the seed that attracts ants, recruiting them to aid in seed dispersal.

Female flowers and fruits forming on castor bean.

Female flowers and fruits forming on castor bean.

All parts of the plant are toxic, but the highest concentration of toxic compounds is found in the seeds. The main toxin is ricin, a carbohydrate-binding protein that inhibits protein synthesis. The seeds need to be chewed or crushed in order to release the toxin, so swallowing a seed whole is not likely to result in poisoning. However, if seeds are chewed and consumed, 1-3 of them can kill a child and 2-6 of them can kill an adult. It takes several hours (perhaps several days) before symptoms begin to occur. Symptoms include nausea, vomiting, severe stomach pain, diarrhea, headaches, dizziness, thirst, impaired vision, lethargy, and convulsions, among other things. Symptoms can go on for several days, with death due to kidney failure (or multisystem organ failure) occurring as few as 3 and as many as 12 days later. Death isn’t imminent though, and many people recover after a few days. Taking activated charcoal can help if the ingestion is recent. In any case, consult a doctor or the Poison Control Center for information about treatments.

The seeds of castor bean are occasionally used to make jewelry. This is not recommended. In The North American Guide to Common Poisonous Plants and Mushrooms, the authors warn that “drilling holes in the seeds makes them much more deadly because it exposes the toxin.” Wearing such jewelry can result in skin irritation and worse. The authors go on to say that “more than one parent has allowed their baby to suck on a necklace of castor beans.” I doubt such parents were pleased with the outcome.

castor bean seeds

Castor beans are grown agriculturally for the oil that can be extracted from their seeds. Due to the way its processed, castor oil does not contain ricin. The leftover meal can be fed to animals after it has been detoxified. Castor oil has been used for thousands of years, dating as far back as 5000 BC when Egyptians were using it as a fuel for lamps and a body ointment, among other things. Over the centuries it has had many uses – medicinal, industrial, and otherwise. It makes an excellent lubricant, is used in cosmetics and in the production of biofuel, and has even been used to make ink for typewriters. One of its more popular and conventional uses is as a laxative, and in her book, Wicked Plants, Amy Stewart describes how this trait has been used as a form of torture: “In the 1920’s, Mussolini’s thugs used to round up dissidents and pour castor oil down their throats, inflicting a nasty case of diarrhea on them.”

A couple of years ago, I grew a small stand of castor beans outside my front door. I was impressed by their rapid growth and gigantic leaves. I also enjoyed watching the fruits form. By the end of the summer, they were easily taller than me (> 6 feet). I collected all of the seeds and still have them today. I knew they were poisonous at the time, but after doing the research for this post, I’m a little wary. With a great collection of castor bean seeds comes great responsibility.

The castor beans that once grew outside my front door.

The castor beans that once grew outside my front door.

There is quite a bit of information out there about castor beans and ricin. If you are interested in exploring this topic further, I recommend this free PubMed article, this Wikipedia page about incidents involving ricin, this article in Nature, and this entry in the Global Invasive Species Database. Also check out Chapter 11 (“Death by Umbrella”) in Thor Hanson’s book, The Triumph of Seeds.