Poisonous Plants: Lima Beans

I don’t recall being a picky eater as a child, but one food I could barely stomach was lima beans. The smell, the texture, the taste, even the look of them, really didn’t sit well with me. I know I’m not alone in this sentiment. Lima beans are a popular thing to hate, and I have avoided them ever since I was old enough to decide what was allowed on my plate. To be fair, the only lima beans I remember trying were the ones included in the familiar bag of frozen mixed vegetables, which might explain why I didn’t like them. But little did I know there is another reason to avoid them – lima beans are poisonous.

That’s a strong statement. In case you’ve eaten lima beans recently or are about to, I should ease your concerns by telling you that you have little to worry about. Commonly cultivated lima beans are perfectly safe to eat as long as they are cooked properly, and even if they are eaten raw in small doses, they are not likely to hurt you. But again, why are you eating lima beans? They’re gross.

lima beans in cans

Phaseolus lunatus – commonly known as lima bean as well as a number of other common names – is in the legume family (Fabaceae) and is native to tropical America. It is a perennial, twining vine that reaches up to 5 meters. It has trifoliate leaves that are alternately arranged, and its flowers are typically white, pink, or purple and similar in appearance to pea flowers and other flowers in the legume family. The fruits are hairy, flat, 5 – 10 cm long, and often in the shape of a half moon. The seeds are usually smooth and flat, but are highly variable in color, appearing in white, off-white, olive, brown, red, black, and mottled.

P. lunatus experienced at least two major domestication events – one in the Andes around 4ooo years ago and the other in Central America more than 1000 years ago. Studies have found that the first event yielded large seeded varieties, and the second event produced medium to small seeded varieties. Wild types of P. lunatus have been given the variety name sylvester, and cultivated types are known as variety lunatus; however, these don’t appear to be accepted names by plant taxonomists and perhaps are just a way of distinguishing cultivated plants from plants growing in the wild, especially in places where P. lunatus has become naturalized such as Madagascar.

Distinguishing wild types from cultivated types is important though, because wild types are potentially more poisonous. Lima bean, like several other plants we eat, contains compounds in its tissues that produce cyanide. These cyanide producing compounds are called cyanogenic glucosides and are present in many species of plants as a form of defense against herbivores. The predominant cyanogenic glucoside in lima beans is called linamarin, which is also present in cassava and flax.

Fruits of lima bean (Phaseolus lunatus) - photo credit: wikimedia commons

Fruits of lima bean (Phaseolus lunatus) – photo credit: wikimedia commons

In order for lima beans to poison you, they must be chewed. Chewing brings linamarin and the enzymes that react with it together. Both compounds are present in the cells of lima beans, but they reside in different areas. Once they are brought together, a reaction ensues and hydrogen cyanide is produced. Because cyanide isn’t produced until after the plant is consumed, the symptoms of cyanide poisoning can take a little while to occur – often several hours.

Cyanide poisoning is not a pretty thing. First comes sweating, abdominal pain, vomiting, and lethargy. If the poisoning is severe, coma, convulsions, and cardiovascular collapse can occur. There are treatments for cyanide poisoning, but if treatment comes too late or if the dose is large enough, death results.

Cassava (Manihot esculenta) is particularly well known for its history of cyanide poisonings. It is a staple crop of people living in tropical areas of Africa and South America. Humans can readily metabolize small amounts of cyanide, and processes like crushing and rinsing, cooking, boiling, blanching, and fermenting render cassava safe to eat. However, consuming cassava that isn’t prepared properly on a consistent basis can result in chronic illnesses, such as konzo, which is a major concern among cultures in which cassava is an important food source.

I guess I should reiterate at this point that most cultivated lima beans contain low (read “safe”) levels of cyanogenic glucosides and, particularly when cooked, are perfectly safe to eat. I’m still not totally convinced that I should eat them though. While researching this article I came across numerous sites claiming that lima beans are delicious while offering various recipes to prove it. I even came across this story in which a self-proclaimed “lima bean loather” was converted to the side of the lima bean lovers. I don’t fancy myself much of a cook, so I’m hesitant to attempt a lima bean laden recipe for fear that it will only make me hate them more. If anyone out there thinks they can convince me otherwise with their tasty creation, be my guest.

And now a haiku:

You are lima beans
I despised you as a child
Perhaps unfairly?

Follow these links to learn more about cyanide producing crops and lima beans:


Texas State Flower

The state flower of Texas blooms in early spring. At least most of them do anyway. Some don’t bloom until late spring and others bloom in the summer. The reason for the staggered bloom times is that the state flower of Texas is not one species but six. All are affectionately referred to as bluebonnets and all are revered by Texans.

As the story goes, at the beginning of the 20th century the Texas legislature set out to determine which flower should represent their state. One suggestion was the cotton boll, since cotton was a major agricultural crop at the time. Another suggestion was a cactus flower, because cacti are common in Texas, are long-lived, and have very attractive flowers. A group of Texas women who were part of the National Society of Colonial Dames of America made their pitch for Lupinus subcarnosus, commonly known as buffalo clover or bluebonnet. Ultimately, the nomination from the women’s group won out, and bluebonnets became an official state symbol.

The debate didn’t end there though. Many people thought that the legislature had selected the wrong bluebonnet, and that the state flower should be Lupinus texensis instead. Commonly known as Texas bluebonnet, L. texensis is bigger, bolder, and more abundant than the comparatively diminutive L. subcarnosus. This debate continued for 70 years until finally the legislature decided to solve the issue by including L. texensis “and any other variety of bluebonnet not heretofore recorded” as the state flower of Texas.

Lupinus texensis - Texas bluebonnet

Lupinus texensis (Texas bluebonnet) bravely growing in Idaho

According to Mr. Smarty Plants, the list of Texas state flowers includes (in addition to the two already mentioned)  L. perennis, L. havardii, L. plattensis, and L. concinnus. Most on this list are annuals, and all are in the family Fabaceae – the pea family. Plants in this family are known for their ability to convert atmospheric nitrogen into plant available nitrogen with the help of a soil dwelling bacteria called rhizobia. The genus Lupinus includes over 200 species, most of which are found in North and South America. Others occur in North Africa and the Mediterranean. Plants in this genus are popular in flower gardens, and there are dozens of commercially available hybrids and cultivars.

L. subcarnosus is sometimes referred to as sandy land bluebonnet and occurs mainly in sandy fields and along roadsides. L. texensis is a Texas endemic; its native range includes the prairies and open fields of north and south central Texas. It is now found throughout Texas and bordering states due to heavy roadside plantings. L. perennis is the most widespread Texas bluebonnet, occurring throughout the eastern portion of the U.S. growing in sand hills, woodland clearings, and along roadsides. L. havardii is the largest of the Texas bluebonnets. It has a narrow range, and is found in a variety of soil types.  L. plattensis is a perennial species and occurs in the sandy dunes of the Texas panhandle. L. concinnus is the smallest of the Texas bluebonnets and is found mainly in sandy, desert areas as well as some grasslands.

Lupinus concinnus (...) - photo credit: www.eol.org

Lupinus concinnus (Nipomo Mesa lupine) – photo credit: www.eol.org

A legend surrounds the rare pink bluebonnet.

A legend surrounds the rare pink bluebonnet

Read more about Texas bluebonnets here and here.

“I want us to know our world. If I lived in north Georgia on up through the Appalachians, I would be just as crazy about the mountain laurel as I am about bluebonnets.” – Lady Bird Johnson