by Amy Stewart
OFFENSIVE
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.
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.
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.
PAINFUL
DON’T TREAD ON ME
Some plants get around by hitching a ride on an animal or an unsuspecting hiker. These plants are the most aggressive in the plant kingdom, practically leaping out to sink their teeth into a bare ankle or grab the tail of a golden retriever. The tiny, fishhook-like barbs mean that the more you pull on them, the more embedded they will become.
JUMPING CHOLLA
Cylindropuntia fulgida or
TEDDY BEAR CHOLLA
C. bigelovii
Cacti native to the southwestern United States. Hikers swear that the plants reach out and grab boots and pants legs. But in fact the spines are so strong that even the slightest grip is enough to cause one segment of the plant to break away. Don’t try pulling it out; it will only stick to your hand. Experienced travelers carry a comb and use it to brush the plant away in one swift, painful motion.
GRAPPLE PLANT OR DEVIL’S CLAW
Harpagophytum procumbens
A tough, perennial vine found in South Africa. Its barbed seedpod can reach several inches in diameter, and each spine resembles a grappling hook, earning it
its name. The plant produces beautiful pink flowers that resemble morning glory, but its oversized and painful seeds make it a menace for farmers and ranchers grazing livestock. Grapple plant does try to make up for the pain it causes: extracts of the roots have become a popular alternative remedy for treating pain and inflammation.
UNICORN PLANT
Proboscidea louisianica, P. altheaefolia, or P.parviflora
Native to the southern and western United States, this plant sprawls along the ground and resembles a squash vine. It sports showy pink or yellow trumpet-shaped blossoms that produce a seedpod with long, curved hooks that easily attach to shoes or hooves. The seed itself is covered in smaller, sharp spines. Also called devil’s claw, devil’s horn, or ram’s horn
MOUSE TRAP TREE
Uncarina grandidieri
A small tree native to Madagascar, popular among tropical plant enthusiasts and found in botanical gardens throughout the United States. It produces gorgeous three-inch-long yellow flowers that give way to green fruit covered in otherwordly spines. Each spine has a tiny hook on the end; as the fruit dries, the remaining seedpod becomes a real hazard. It could certainly snare a mouse, and humans who have been caught in its grip report that attempting to remove the seedpods is like getting caught in a Chinese finger trap.
FOXTAIL
Hordeum murinum
A species of wild barley that produces the long, barbed seed heads that get embedded in dogs’ fur in summer. However, the common name “foxtail” is also applied to a number of grasses that have similar seed heads. For example, ripgut grass (Bromus diandrus) is so tough that it can perforate the stomach lining of animals and actually kill them.
Foxtails sport tiny barbs that once embedded under the skin can be impossible to see and difficult to remove. The outer coating of the seed-pods contains a bacterium that makes it easier for the barbs to work into the skin and even travel through the body. Dogs are the most susceptible; veterinarians have found foxtails inside their brains, lungs, and spinal cords.
COCKLEBUR
Xanthium strumarium
A widespread summer weed in the aster family; it is native to North America but has become invasive worldwide. Cocklebur produces small seedpods covered in thorns, and although the pods are not difficult to remove, they have been known to ruin the wool of grazing sheep. The seeds are poisonous, and while most humans would not be tempted to munch on them, they can kill livestock.
BURDOCK
Arctium lappa, A. minus, others
Produces thistle-shaped burrs that grab clothing and fur; leaves and stems irritate the skin. Burdock burrs are comparatively easy to remove, but they have the same fishhook structure of other stickers and grapples. This structure caught the attention of George de Mestral, the Swiss engineer who based his invention, Velcro, on the burdock burrs he found in his dog’s fur after a walk.
SAND BURR AND GRASS BURR
Cenchrus echinatus and C. incertus
These invasive grasslike plants have naturalized across the southern United States. They conceal themselves in lawns and produce small, sharp stickers that torture picnickers and punish children who dare to run across the yard barefoot. The burrs flourish in sandy soil with low fertility. They can irritate the eyes and lips of livestock, causing ulcers that can get infected. Control is difficult; some Southerners exact revenge by brewing sand burr wine with the burrs, grape juice, sugar, and Champagne yeast.
The outer coating of the seedpods contains a bacterium that makes it easier for the barbs to work into the skin and even travel through the body.
Dogs are the most susceptible; veterinarians have found foxtails inside their brains, lungs, and spinal cords.
DEADLY
Yew
TAXUS BACCATA
In 1240 Bartholomaeus Anglicus described the yew in his encyclopedia, On the Properties of Things, as “a tree with venim and poison.” It’s fitting, perhaps, that this highly toxic tree has come to be known as the graveyard tree in England. The plant earned that name not for its ability to send people to an early grave, but because Roman invaders began offering church services in the shade of yew trees, hoping that this would appeal to the pagan population. Today ancient yew trees are still found near churches in the English countryside.
FAMILY:
Taxaceae
HABITAT:
Temperate forests
NATIVE TO:
Europe, northwest Africa, Middle East, parts of Asia
COMMON NAMES:
Common yew, European or English yew
The sight of these yew trees in cemeteries inspired Alfred, Lord Tennyson, to write, “Thy fibres net the dreamless head / Thy roots are wrapt about the bones.” In fact, an ancient churchside yew growing in the English village of Selborne was toppled during a storm in 1990, and the bones of the long-ago dead were found tangled in its roots.
The yew is a slow-growing evergreen that can live two or three centuries, but it is difficult to date mature trees because the dense wood doesn’t always produce rings. The fine, needlelike leaves and red fruit make it an attractive landscape tree that can easily reach seventy feet in height. In England yews are often pruned to form a formal hedge; the Hampton Court Palace’s legendary three-hundred-year-old hedge maze is now planted almost entirely with yew.
An ancient churchside yew growing in the English village of Selborne was toppled during a storm in 1990, and the bones of the long-ago dead were found tangled in its roots.
Every part of the yew is poisonous with the exception of the flesh of its red berrylike fruit (called an aril), and even that contains a toxic seed. The aril itself is slightly sweet, making it a temptation for children. Eating just a few seeds or a handful of leaves will bring on gastrointestinal symptoms, a dangerous drop in pulse rate, and possible heart failure. One medical manual mournfully noted that “many victims never described their symptoms” because they were found dead. Yews pose a particular hazard to pets and livestock. A veterinary medicine article stated that “often, the first evidence of yew toxicosis is unexpected death.”
In Caesar’s Gallic Wars, suicide by yew became a way to avoid facing defeat. Catuvolcus, king of a tribe who lived in what is now Belgium, was “worn out by age . . . unable to endure the fatigue either of war or flight” and “destroyed himself with the juice of the yew-tree.” Pliny the Elder wrote that “travelers’ vessels” made of yew wood and filled with wine could poison people who drank from them.
But before ripping that yew tree out of the garden, consider this: In the early 1960s a team of researchers from the National Cancer Institute discovered that yew extract had potent antitumor properties. Now the drug paclitaxel, or Taxol, is used to fight ovarian, breast, and lung cancers and shows promise for many others. Companies like Limehurst Ltd. collect hedge clippings from English gardens for the pharmaceutical industry. Research indicates that yew trees even secrete the drug into the dirt, opening up the possibility that cancer-fighting compounds can be extracted without harming the trees.
Meet the Relatives Relatives include Japanese yew, Taxus cuspidata, which is native to Japan but grows throughout North America, Pacific or western yew, T. brevifolia, found in the western United States, and Canadian yew, T. canadensis, found in Canada and the eastern United States, which is also called American yew or ground hemlock.
End Notes
Antidote
Throughout the twentieth century, syrup of ipecac was recommended as a treatment for accidental poisoning. Ipecac is made from the roots of Psychotria ipecacuanha, a flowering shrub in Brazil. The syrup proved to be a powerful emetic, causing violent vomiting that might bring up the poison. Ipecac syrup eventually made its way into the medicine chest of every family with young children as a remedy for accidental poisoning.
However, the American Academy of Pediatrics and other medical groups now discourage the use of ipecac except if recommended by a doctor or poison control center. The syrup is abused by people with bulimia; in fact, it contributed
to the death of singer Karen Carpenter. Ipecac has also been used in a few high-profile poisoning cases in which parents poison their children to get attention, a syndrome called Munchausen syndrome by proxy. Doctors also have more effective treatments for poisoning cases and believe that home use of ipecac may delay better treatment and mask symptoms. Instead, they recommend calling a poison control center or seeking immediate medical attention.
Briony
THE ARTIST AND THE PLANT
Briony Morrow-Cribbs creates copper etchings, fine bound books, and ceramic “cabinets of curiosity” that reflect her fascination with the ways in which the rational language of science meets the grotesque and absurd natural world. A graduate of the Emily Carr Institute of Art and Design, Morrow-Cribbs’s work has been exhibited around the world. She resides in Brattleboro, Vermont, and is represented by the Davidson Gallery in Seattle. She is also the cofounder of Twin Vixen Press.
Briony shares her name with a wicked plant, B. cretica. Native to central and eastern Europe, this sturdy, twining vine produces red berries that cause vomiting, dizziness, and even respiratory failure. White bryony, B. alba, has been called “the kudzu of the Pacific Northwest” for its invasive behavior in that region. All plants in the Bryonia genus are poisonous to humans and livestock; common names include snakeweed, bastard turnip, and devil turnip.
