Harmful Plants

Introduction

Plants have a variety of mechanisms and adaptations to protect themselves. Because they are immobile, they must have other means to protect themselves from herbivorous animals and other predators. Many plant species have evolved physical defenses to avoid ingestion by other species such as thorns, trichromes, prickles, or spines. Depending on the specific predator, the structural defenses of plants can injure, deter, or kill the grazer. Other physical defenses include the altered texture or composition of plant tissue and leaves, production of sap or gummosis, armored or protected fruit, and the internal production of defense compounds such as resins, lignins, silica, and wax. On top of physical defenses, plants can also influence the behavior, growth, and survival of herbivores through chemical defenses. These chemical compounds evolve separately from the substances involved in photosynthesis and metabolic activities. Most of these substances are secondary metabolites, which are organic compounds produced as bi-products during the synthesis of primary metabolites that are not directly involved in the growth or development of the plant. These chemical compounds can be classified into three groups: nitrogen compounds (alkaloids), terpenoids, and phenolics. These chemicals can act as repellents or toxins, or to reduce plant digestibility. Although these defenses are intended for predators, many times they can have deleterious effects on humans following contact or ingestion.

Most people do not associate or understand the potential harmful effects presented by many plant species. In order to inform the general public about the possible deleterious effects of many plant species, a census of the harmful vegetal life found on the Southwestern University campus was conducted. The parameters and characteristics defining harmful were any form of vegetation whose physical touch or ingestion was detrimental to a human’s health. Using plant databases (Texas A&M Forest Service, Texas Plant Information Database, etc.), species were identified, characterized, located, and cataloged. Using this information all the data was organized and presented in three components: a map of the Southwestern University campus designating the locations of all harmful species, a corresponding table of all the species with their respective medical symptoms and treatments, and a picture ID of each species. All the compiled information, along with additional information regarding medicinal and invasive species on campus, is accessible on a public blog forum (www.bio50-434.blogspot.com). The goal of this survey was to provide an accurate and available source of information regarding harmful plant species on the Southwestern University campus. 

Bur Oak-- Quercus macrocarpa

Found at SU? Yes
General Information The bur oak is a fire-resistant and strongly drought resistant tree that grow in the open, near waterways, and in more forested areas. The acorns are the largest of any North American oak species and are an important source of food for wildlife. Bur oaks make great ornamental trees. 
Toxic/Harmful Part Foliage, acorns
Symptoms Affects kidneys gradually. Symptoms appear only after several days or weeks. Takes a large amount for poisoning.
Causes The dehydrated tergallic acid C-glucoside and tergallic acid O-glucoside components induce the displayed symptoms. 

Texas Mountain laurel-- Sophora secundiflora 

Found at SU? Yes

General Information The Texas Mountain laurel is an evergeen, multi-trunked, ornamental shrub that prefers dyr, rocky, and calcareous soils. Although the shrub's seeds have medicinal purposes (strained liquid from crushed boiled seeds used as an ear ache remedy), they are known mostly for their toxic nature. The Native Americans used these seeds to create necklaces as well as a hallucinogenic drug. The red seeds contain the highly poisonous alkaloid cystine (or sophorine), which is related to nicotine and is used as a narcotic and hallucinogen. 

Toxic/Harmful Part All parts

Symptoms Fatal. Produces nausea and vomiting, depression, difficulty breathing, prostration, and coma.

Ashe Juniper-- Juniperus ashei

Found at SU? Yes

General Information Ashe Juniper is a small, evergreen, invasive shrub that is extremely common throughout central Texas. It forms extensive forests and "cedar breaks" on the limestone hills and slopes of the Edward Plateau. The strips of bark from this shrub are used as the primary source and material for nests made by golden-cheek warblers. The shrub produces large amounts of pollen, resulting in outbreaks of "cedar fever."

Toxic/Harmful Parts Pollen

Symptoms Seasonal allergy that causes runny nose, itchy and watery eyes, nasal blockage, and sneezing. Some sufferers mention fatigue, facial discomfort, headache, sore throat, and loss of smell as other symptoms. 

Japanese Privet-- Ligustrum japonicum

Found at SU? Yes

General Information Japanese privet is an invasive, evergreen shrub that is native to central and southern Japan. The fruit of this plant have both toxic and medicinal purposes. On one hand, the fruit is used in herbal medicine as a cardiotonic, diuretic, laxative, and tonic treatment. When ingested, the berries can cause mild toxic symptoms in humans. Also, the pollen from this shrub, which is known to induce asthma and eczema, is a huge problem in Australia and New Zealand.

Toxic/Harmful Parts Flowers, leaves, or berries. Pollen.

Symptoms Common symtoms include upset stomach, nausea, and diarrhea. Pollen causes asthma and eczema in sufferers. 

Greenbrier-- Smilax bona-nox

Found at SU? Yes

General Information The thorns of this plant allow it to grow over other plants and trees, forming dense impenetrable thickets. This plant is a very damage-resistant plant that is capable of growing back from its rhizomes after being cut down or burned. It is an important food source as well as viable shelter. The thorny thickets help to shelter small animals from predators who cannot enter the prickly tangle. Besides the thorns which can cause physical damage, the shrub is fairly medicinal. Extract from the roots can be used to make sarsaparilla drink, root beer, and herbal drinks. The root extracts can be used to treat gout and premenstrual syndrome. 

Toxic/Harmful Parts Thorns

Symptoms Interaction can cause skin irritation or breakage. 

Paloverde-- Parkinsonia aculeata

Found at SU? Yes

General Information Paloverde is an invasive, perennial flowering tree that is resistant to drought and prefers to grow in areas with prominent sun exposure. It is native to the Sonoran and Chihuahan deserts of southwestern United States. It is a major invasive species in Australia, Africa, and Hawaii.  These areas have utilized many control methods including biological control (introduction of insect species), fire, mechanical removal, and herbicides. 

Toxic/Harmful Parts Spines

Symptoms Interaction can cause skin irritation or breakage. 

Heavenly Bamboo-- Nandina domestica

Found at SU? Yes

General Information Heavenly Bamboo is an invasive, flowering evergreen shrub that is native to eastern Asia. The species in considered invasive in Texas and Florida. Every part of the plant is toxic, containing hydrocyanic acid, and ingestion can lead to fatality. The berries are generally non-toxic to humans but they are considered toxic to cats and grazing animals. The berries are known to contain the alkaloid nantenine, which is an antidote to MDMA (ecstasy). 

Toxic/Harmful Parts All parts

Symptoms Symptoms include mild gastrointestinal upset. Takes a large amount for poisoning.  

Chinaberry-- Melia azedarach

Found at SU? Yes

General Information Chinaberry is an invasive, deciduous tree native Pakistan, India, Indochina, Southeast Asia, and Australia. Chinaberry trees are used mainly for their high quality timber. The fruits of this tree contain neurotoxins and unidentified resins and are toxic to humans. Additionally, the leaves have been used as a natural insecticide and are highly poisonous if ingested. 

Toxic/Harmful Parts Fruits, leaves

Symptoms Symptoms include loss of appetite, vomiting, constipation or diarrhea, bloody feces, stomach pain, pulmonary congestion, cardiac arrest, rigidity, lack of coordination, and weakness. 

Yarrow-- Achillea millefolium

Found at SU? Yes

General Information Yarrow is a flowering plant native to the temperate regions of the Northern Hemisphere in Asia, Europe, and North America. Yarrow used to be known as herbal militaris due to its use in war as a topical tourniquet, preventing flow of blood from wounds. The plant has multiple medicinal purposes and is purported to be a diaphoretic, astringent, tonic, stimulant, and mild aromatic. Additionally, yarrow was used in traditional Native American herb medicine. Yarrow can also induce deleterious effects on humans such as severe allergic skin reactions. 

Toxic/Harmful Parts Pollen

Symptoms Pollens may cause severe allergic skin rashes. 

Dandelion-- Taraxacum officinale

Found at SU? Yes

General Information Dandelion is a flowering herbaceous perennial plant that grows in temperate regions all around the world. It is considered a weed but it has many uses such as for food preparation and as a medicinal herb. The flowers are used to make dandelion wine, the greens are frequently used in salads, the roots are used as a coffee substitute, and the plant was used by Native Americans as food and medicine. The dandelion also has some negative connotations including the development of fasciolosis following consumption of the leaves. 

Toxic/Harmful Parts All parts

Symptoms Pollen may cause allergic reactions when eaten. Latex in the stems and leaves may cause contact dermatitis. Consumption of the leaves may cause fasciolosis.