Wicked Plants: The Weed That Killed Lincoln's Mother and Other Botanical Atrocities - Amy Stewart (2009)

GUESS WHO’S COMING TO DINNER

Plants don’t just arm themselves with poisons and thorns. Some of them enlist the help of insects as well. Many seemingly innocuous plants act as host to stinging ants, wasps, and other creatures, providing them food and shelter in exchange for their services.

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VALLEY OAK

Quercus lobata

   

Many oak trees host species of wasps, but California’s valley oak is one of the best-known and most hospitable of all the oaks. The process begins when a wasp lays an egg on an oak leaf. The plant cells start multiplying at an unusually high rate, forming a kind of protective cocoon called a gall. Eventually the egg hatches into a larva, and the gall, which can get to be the size of a baseball, becomes a home to the larva and also gives it something to eat. The larvae emerge as full-grown wasps.

One species of wasp causes the valley oak to form small galls that drop off the tree. The galls can jump around for a few days as the wasp inside tries to break free, earning them the name “jumping oak galls.”

FIGS

Ficus spp.

   

The relationship between figs and wasps is one of the most complicated in the plant kingdom. Figs don’t actually produce fruit—that fleshy, juicy appendage that people eat is actually more like a swollen bit of stem with the remnants of the flower inside and a tiny opening at one end. Fig wasps, which can be as small as ants, breed inside this fruit-like structure. Once they have bred, the pregnant female flies to another fig, crawls inside, pollinating it in the process, and lays her eggs. She usually dies inside the fig after her work is done. The larva munch on the fig as they grow, and once they reach full size, they mate with each other. The male chews a hole through the fig to allow the female to escape, and then he dies, having served his only purpose in life. After the wasps are gone, the “fruit” continues to ripen, eventually becoming a food source for birds and humans alike.

Fig lovers may wonder if they’ve been eating wasp corpses all this time; in fact, many commercial fig varieties don’t require pollination at all and others are only pollinated by wasps but don’t host the eggs.

MEXICAN JUMPING BEANS

Sebastiana pavoniana

   

Jumping beans are actually the seeds of a shrub native to Mexico. A small, brown moth lays its egg on the seedpod, and the egg grows into a larva that chews its way into the seedpod then closes the hole with the silk it produces as it grows. The larva is sensitive to warmth and will start to twitch if the seed is held in the hand. After several months, the larva will form a pupa and then emerge as an adult, which will live for only a few days.

ANT PLANT

Hydnophytum formicarum

   

This southeast Asian plant is an epiphyte, meaning that it grows on another tree for support. The base of the plant swells and forms a large hollow space that provides a home to an entire colony of ants. The ants build multichambered apartments, with a separate space for the queen, a nursery for their young, and a space where they can deposit their garbage. In exchange for providing a home for the ants, the plant sustains itself with the nutrients from the ant’s waste products.

RATTAN

Daemonorops spp.

   

Rattans are palms that grow in tropical rain forests, where their long, sturdy stems are in great demand for cane and wicker furniture. A single plant can reach over five hundred feet tall, often relying on other trees for support. Ants make themselves at home in the bases of rattan plants, and if they sense that the plant is under attack, they will beat their heads against the plant, causing the whole structure to rattle and shake. Once they’ve raised the alarm, ant colonies have been known to go on the attack, vigorously defending their home against rattan harvesters.

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DEADLY

White Snakeroot

EUPATORIUM RUGOSUM (SYN. AGERATINA ALTISSAMA)

Frontier life was harsh enough without the frightening possibility that fresh milk, butter, or meat could be contaminated by a deadly plant. Milk sickness was an all-too-common hazard of early farm life in America: entire families succumbed to the disease after suffering from symptoms that included weakness, vomiting, tremors, and delirium. Cattle also showed symptoms of the disease. Horses and cows would stagger around until they died, and farmers stood by helplessly, not realizing that a plant the cattle grazed on was to blame. The disease was so common that the names Milk Sick Ridge, Milk Sick Cove, and Milk Sick Holler are still attached to places in the South where the disease was rampant.

FAMILY:
Asteraceae (or Compositae)

HABITAT:
Woodlands, thickets, meadows, and pastures

NATIVE TO:
North America

COMMON NAME:
White sanicle

One of the most famous victims of milk sickness was Nancy Hanks Lincoln, mother of Abraham Lincoln. She fought the disease for a week but finally succumbed, as did her aunt and uncle and several other people in the small town of Little Pigeon Creek, Indiana. She died in 1818 at the age of thirty-four, leaving behind nine-year-old Abraham Lincoln and his sister, Sarah. Lincoln’s father built the coffins himself; young Abraham helped by carving the pegs for his mother’s casket.

During the nineteenth century a few doctors and farmers independently discovered that white snakeroot was the cause of this illness, but news traveled slowly in those days. An Illinois doctor named Anna Bixby noticed the seasonality of the disease and speculated that it might have to do with the emergence of a particular plant in summer. She wandered the fields until she found white snakeroot, and she fed the weed to a calf to confirm that it caused the disease. She led a campaign to eradicate the plant from her community and almost eliminated milk sickness in that area by about 1834. Unfortunately, her attempts to notify authorities fell on deaf ears, perhaps because women doctors were not taken seriously.

One of the most famous victims of milk sickness, caused by white snakeroot, was Nancy Hanks Lincoln, mother of Abraham Lincoln.

Another early discovery was made by a farmer named William Jerry in Madison County, Illinois, in 1867, who realized that the disease occurred after his cattle grazed on white snakeroot, but it was not until the 1920s that white snakeroot was widely recognized as the cause. Eventually farmers learned to fence their cattle or eradicate the weed from pastures to prevent the disease.

White snakeroot grows to four feet tall and produces small, white clusters of flowers similar in shape to Queen Anne’s lace. The plant is still found in the woods across eastern North America and throughout the South. The toxic ingredient, tremetol, remains active even after the plant has dried, making it a threat in hayfields as well as pastures.

Meet the Relatives     Joe-pye weed, Eupatorium purpureum, a popular plant in butterfly gardens, and boneset, E. perfoliatum, which was once used as a laxative and as a treatment for fever and flu are both related to white snakeroot.

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