July 15, 2018
Plant Talk 9 Poisonous Plants
Hello Plant Enthusiasts!
Some of what’s blooming around me includes Angel’s Trumpet (Brugmansia spp.), Anise Hyssop (Agastache foeniculum), Basil (Ocimum spp.), Bee Balm (Monarda spp.), Bellflowers (Campanula spp.), Black Eyed Susans (Rudbeckia spp.), Black Eyed Susan Vine (Thunbergia alata), Blazing Stars (Liatris spp.), Butterfly Bush (Buddleja davidii), Crepe Myrtle (Lagerstroemia indica), Culver’s Root (Veronicastrum virginicum), Day Lily (Hemerocallis spp.) Dahlia spp., Elecampagne (Inula helenium), Elderberry (Sambucus canadensis), Jimson Weed (Datura stramonium), Lucifer’s Tongue (Crocosmia x crocosmiiflora) Gladiolas (Gladiolus spp.), Hydrangea spp., Marigolds (Tagetes spp.), Mullein (Verbascum spp.), Phlox sp., Rose of Sharon (Hibiscus syriacus), Rose Gentian (Sabatia spp.), Sages (Salvia spp.), Scarlet Rose Mallow (Hibiscus coccineus), Skullcap (Scutellaria lateriflora), Sourwood (Oxydendrum arboreum), Sumac (Rhus spp.), Thimbleweed (Anemone virginiana), Turk’s Cap Lily (Lilium superbum), Queen Anne’s Lace (Daucus carota), Vervain (Verbena spp.), and Zinnia spp.
Relatively few poisonous plants are largely responsible for many people’s aversion/fear of nature, e.g. Poison Ivy/Sumac/Oak (Toxicodendron spp.). These plants are so important to people that they have their own collection of literature (Anderson, 1995; Day, 2008; Hauser & Epstein, 2008). Frank Cook would speak of referring to this plant as sister ivy or sister oak considering the term poison to be pejorative and provocative towards the plant thus potentially even inciting more ire. Either way, this is one to be aware of, as is the fact that the toxin manifests as an allergy by which only some people are affected. Those familiar with areas where Mangoes (Mangnifera indica), Brazilian Pepper (Schinus spp.) and Cashews (Anacardium exelsum) grow will possibly know of potential severe allergic reactions to these foods as well. Interestingly, the non-poisonous red fruited Sumacs (Rhus glabra, R. typhina and spp.) share the same family but represent widely distributed culinary use all over the temperate world and no toxicity that i know of. Surprisingly, the pulp around the seeds of the rather unrelated Gingko has a similar compound to the urushiol in Toxicodendron spp. However, the seed inside of the Gingko is considered a delicacy when cooked though possibly poisonous in a minor way as well (Cox & Ruter, 2013; Crane, 2013; Singh, Kaur, Gopichand, Singh, & Ahuja, 2008)!
When covering a subject like the use and possible ingestion of plants clearly a class concerning the main prevalent poisonous plants and their effects on various forms of life is in order. The phenomenon of plant poisons offers an excellent venue to examine plants at the family level. Some families tend to be have a majority of poisonous members such as the Buttercup (Ranunculaceae), Arum (Araceae), Tomato (Solanaceae), Bittersweet (Celastraceae), Euphorb, (Euphorbiaceae) and Lilies (Liliaceae) as classically described. We have already covered the fact that new descriptions for Lily like plants (Lilioid) have broken them into many separate families. Edibility versus poisonousness does seem to trend out along SOME of these new family lines. For instance many plants formerly in the Lily family are now placed in the Melanthiaceae and Convallariaceae and both new families contain several deadly poisonous members. However, even families that tend to be predominantly poisonous have some exceptions especially depending on proper preparation.
For other families it is not nearly as cut and dry. The Carrot family (Apiaceae) contains a multitude of edible plants. It has many famous well used culinary herbs and spices in particular. Which ones can you think of? However, it also contains some of the most toxic plants in the U.S.A. and the world including Poison Hemlock (Conium maculatum) and Water Hemlock (Cicuta spp.) (Schep, Slaughter, Becket, & Beasley, 2009; Vetter, 2004). Poison Hemlock looks very similar to Queen Anne’s Lace (Daucus carota) and some Biscuitroots (Lomatium spp.) among other relatives. Water Hemlock can look similar to a number of other plants in the family as well like Angelica spp. Several other members of the Apiaceae can also cause skin irritation due to furonocoumarins including Celery (Apium graveolens) Cow Parsnip/Giant Hogweed (Heracleum spp.) and regular Parsnip (Pastinaca sativa).
The Mint family (Lamiaceae) is probably one of the safest groups in the world. However, several members can be toxic in high dosages or in the case of pregnancy including Ale Hoof (Glechoma hederacea), Perilla (Perilla frutescens), Germander (Teucrium spp.) and Pennyroyal (Hedeoma pulegioides) (Duke & Foster, 2014; Frohne & Pfander, 2005; Kingsbury, 1964). i have also heard that the American native Mountain Mint (Pycnanthemum spp.) has a similar compound to Pennyroyal (pugelone), and should possibly be avoided during pregnancy as well. It would be good of course to review all items one might potentially ingest while pregnant with a special lens towards safety…
Big families such as the Aster (Asteraceae) and Bean (Fabaceae) have a broad spectrum of plants. Some are used for food, some for medicine and some are poisonous. Several sources list plants by family which may aid in recognizing these trends (Frohne & Pfander, 2005; Kingsbury, 1964; Muenscher, 1940; Westbrooks & Preacher, 1986). Other books specifically address the interface between plant poisons and drugs (Blackwell, 1990; Wink & Van Wyk, 2008).
A classic statement of toxicology attributed to Paracelsus centuries ago is that “the difference is the dosage”. Therefore, even some poisonous plants may provide powerful medicines through the right means of extraction and appropriate levels of intake. Mayapple (Podophyllum spp.), Poke (Phytolacca americana) and Foxglove (Digitalis spp.) are examples of such a phenomenon. Amount of intake, frequency of use, method of exposure, personal biochemistry and site ecology may all influence the effects of certain plants. The fields of genetics and biochemistry are starting to reveal that plant populations can vary greatly in their phytochemistry on a level within the species (Dhar et al., 2006; Gonick, 2014; Jarić, Mitrović, & Pavlović, 2015; Jia & Zhao, 2009; Ogunwenmo, Idowu, Innocent, Esan, & Oyelana, 2007; Schlag & McIntosh, 2006; Searels, Keen, Horton, Clarke, & Ward, 2013).
Can you think of some reasons why this might be?
Some plants are toxic to livestock but not to humans and vice versa. This phenomenon largely has to do with levels of typical intake and differing digestive regimes. Humans have of course historically learned plant uses from other animals which is a practice in one way labeled bioethnopharmacognosy. However, this is NOT a very dependable and fail-proof way to test if something is wholesome for human intake! A number of books look at human poisoning by plants from an historical perspective including how humans can be poisoned by the intake of animal products like milk containing poisonous compounds and how people have used plant poisons intentionally through history (Brown, 2018; Stewart, 2009, 2016; Stuart, 2004).
Numerous compounds are responsible for the phenomenon of plant poisoning. The most prevalent amongst them are various types of alkaloids. Elpel (2004, p. 203 2014, p. 219) has a great write up in the back of Botany in a Day on various plant compounds discussed below. Other compounds typically cited include amines, glycocides, oxalates, polypeptides, resins, saponins minerals and compounds causing photosensitivity (Kingsbury, 1964). Many other plants also contain compounds that don’t fall into the above listing but may still cause health problems i.e. hydroquinone in Cocklebur (Xanthium sp.) and thiaminase in Bracken Fern (Pteridium aquilinum) (Kingsbury, 1964). Lisa Ganora (2009) is the author of a relatively accessible and affordable text on the subject of phytochemistry. Of course there are a number of college type textbooks as well (Bruneton & Hatton, 2008; Malviya, 2015).
Plants containing pyrrolizidine alkaloids typically are located in the Bean, Borage (Boraginaceae) and Aster families (Biller, Boppré, Witte, & Hartmann, 1994; Nelson, Shih, & Balick, 2007). Common knowledge of these compounds is relatively recent. Therefore, traditional internal use of plants such as Comfrey (Symphytum officinale) which has such compounds is now often discouraged.
Oxalates are compounds typically found in the Amaranth (Amaranthaceae incl Chenopodiaceae) Buckwheat (Polygonaceae) and Wood Sorrel (Oxalidaceae) families. Purslane (Portulaca oleracea) in the (Portulacaceae) also contains soluble oxalates. These compounds have the potential to leach calcium from the body if not prepared in the appropriate way. One method of preparation is through boiling or blanching as the acid goes into the water. Some individuals are particularly susceptible to the formation of stones made of calcium oxalate as well. Care should be exercised in not consuming excessive amounts of members from these families in a raw form. However, researcher Dr. John Kallas (2010) debates the role of oxalic acid in causing health issues in people regarding kidney stones in particular.
Plants in the Araceae family contain calcium oxalate crystals that may cause an intense burning sensation upon digestion. Fish Tail palm (Caryota sp.) fruits also contain calcium oxalate crystals as i had to learn the hard way in a tropical locale once. i was going off the idea espoused by Frank Cook that all palm fruits are edible… Remember that nature is not a fan of absolutes like “all” and “never”. The kernel inside even the Fish Tail is edible apparently once the pulp is removed. However, that pulp can even be caustic topically and should be removed with care.
Important glycocides including goitrogenic substances that may inhibit proper thyroid function are present in some members of the Mustard (Brassicaceae) and Amaranthaceae families. Ranunculin is a glycocide in the Buttercup (Ranunculaceae). Cardiac glycocides are the most powerful. They are typically found in species from the Lily sensu lato, Foxglove (Scrophulariaceae) and Dogbane (Apocynaceae) families. The Apocynaceae now includes the formerly distinct Milkweed family (Asclepiadaceae). One side note is that many members of the Scrophs as traditionally described including Foxglove have been moved to the Plantaginaceae and Orobanchaceae families. Hedge Hyssop (Gratiola) is an outlier from the Lamiaceae that also contains cardiac glycocides.
Cyanogentic glycocides are primarily present in members of the Grass (Poaceae), Bean (Fabaceae), Mochatel (Adoxaceae) and Rose (Rosaceae) families. Small amounts of cyanide occur in the seeds of many members of the Rose family but are normally not an issue at typical rates of consumption by humans. The potential for poisoning of livestock by consumption of the wilted foliage of wild black cherry (Prunus serotina) is well known (Kingsbury, 1964). Cyanogentic compounds also occur in Hydrangea and Elderberry (Sambucus spp.) (Nelson et al., 2007). A form of cyanide has also been reported in the exotic invasive Garlic Mustard (Alliaria petiolata) from the Brassicaceae (Cipollini & Gruner, 2007).
Saponins are toxins that have also been used to make soap. A diverse array of plants from several families contain such compounds. A list according to (Kingsbury, 1964) follows.
Beech (Fagus grandifolia) (Fagaceae)
English ivy (Hedera helix) (Araliaceae)
Poke weed (Phytolacca americana) Phytolaccaceae
Ceanothus (Rhamnaceae), Clethra (Clethraceae), Aesculus (Sapindaceae) and Yucca (Agavaceae) all have saponins as well. Elpel includes Lychnis (Caryophyllaceae), Symphoricarpos (Caprifoliaceae) and Cyclamen (Primulaceae) as containing saponins too (Elpel, 2013). Steroidal saponins are also used medicinally in plants like Ginseng (Panax spp.) and Sweet Tea Vine (Gynostemma pentaphylla) (Chang, Chang, Lin, Liu, & Chen, 2005; Cui, Eneroth, & Bruhn, 1999; Razmovski-Naumovski et al., 2005; Schlag & McIntosh, 2006).
Poisoning by the mineral uptake of plants is another potential cause for concern. Excessive amounts of copper may be taken up by plants in areas where a Bordeaux fungicide have been applied for many years. Note that Bordeaux is a mixture even employed by organic farmers as well. Also cadmium may be taken up where triple superphosphate has been applied (Kingsbury, 1964).
Excessive nitrates may especially be taken up by members of the Amaranthaceae, Asteraceae, Poaceae, Brassicaceae and Solanaceae. Out west many plants are known to take up harmful amounts of elements like selenium and one should be especially aware in places with serpentine soils. More can be seen on this in the class covering Phytoremediation.
Plant Poisons That Can Act Topically
Some plants can act topically to cause irritation or photosensitization as mentioned above for the Apiaceae. The photosensitivity can be caused through their effect on the liver including members of the Verbena (Verbenaceae) Pea (Fabaceae) Grass (Poaceae) and Buckwheat (Polygonaceae) families. Notable genera in this regard include Knotweed (Polygonum), Vetch (Vicia), Clover (Trifolium), Oats (Avena), and Verbena (Lippia) (Kingsbury, 1964).
(Hardin & Arena, 1974) compiled a more comprehensive list of 78 plants that grow in the United States which may cause dermatitis. Those that grow in Appalachia and are considered especially important by me are included below.
Trumpet Creeper (Campsis radicans) Bignoniaceae
Spurge (Euphorbia spp.) Euphorbiaceae
Giant Hogweed (Heracleum mantegazzianum) Apiaceae
Wood Nettle (Laportea canadensis) Urticaceae
Stinging Nettle (Urtica dioica) Urticaceae
Posion Ivy/Oak/Sumac (Toxicodendron spp.) Anacardiaceae
Both types of Nettles are choice edibles that can be picked with gloves and deactivated by drying or cooking. The sting of Urtica is also considered to be of medicinal value as well (Duke & Foster, 2014). One of my all-time favorite ethnobotanical memories is witnessing Frank Cook “urticate” the aching legs of our friend and teacher the legendary ethnobotanist Jim Duke at a Warren Wilson College herbal symposium in 2009.
Another source lists even more plants that can irritate the skin (Nelson et al., 2007). In this reference the sources of phytodermatitis are broken down in five categories: mechanical irritants, chemical irritants, allergens, phototoxins and pseudophytodermatitides. The main culprits are the Araceae, Asteraceace, Apiaceae, and Euphorbiaceae.
Toxins from mushrooms and microbes are beyond the scope of the current discussion. However, a couple fungal organisms that act on plant materials do bear mentioning. Ergot (Claviceps spp.) is a commonly occurring toxic fungus on members of the Poaceae (Elpel, 2013; Stewart, 2009). Aflotoxin is a commonly occurring fungus on several kinds of nuts. A number of books deal with the toxins of plants and also cover fungus as well (Blackwell, 1990; Cooper & Johnson, 1997; Kingsbury, 1964; N. J. Turner & Szczawinski, 1995; Nancy J Turner & Aderkas, 2009).
Medicine to Poison
A classic statement attributed to Paracelcus as stated above is that the dose makes the poison. However, some classic medicines and foods have subtle poisons that allow them to get accepted by various cultures potentially to their detriment. Common name confusion can further cloud understanding. The plant sometimes called Red Sage (Lantana camara) Verbenaceae is one example. It is potentially toxic when taken internally which is a common practice in the Caribbean (Julia F. Morton, n.d.; Pour, Latha, & Sasidharan, 2011; Pour & Sasidharan, 2011; Sharma, Makkar, Dawra, & Negi, 1981; Wolfson & Solomons, 1964). Many other plants may act in this way including members of the Aristolochiaceae family due to the presence of Aristolochic acid (Hashimoto et al., 1999; Schaneberg, Applequist, & Khan, 2002). i hope to expand this section in the next iteration. The members of the Asteraceae with pyrrolizidine alkaloids mentioned above would fit into this section as well i.e. Eupatorium spp. and Senecio spp.
Miscellaneous potentially toxic plants
Many other potentially toxic plants that have not been mentioned occur in temperate regions. Horsetail (Equisetum spp.) Equisetaceae, has sometimes been recommended for internal ingestion medicinally but may cause upset due to the presence of silica (Abbe, 1985; Rogers, 2014).
A small fraction of people are sensitive to Pawpaw (Asimina triloba) Annonaceae, either through exposure to the skin or ingestion of the fruit (Kingsbury, 1964). The Annonaceae also has some pretty severe compounds that have been researched thoroughly and may be toxic after extended intake or exposure but at the same time are being researched for use against cancer (Araya et al., 2002; Champy et al., 2005; Harper, Potter, & Gillham, 1947; He et al., 1997; Lannuzel et al., 2002; Levine et al., 2015; McLaughlin, 2008; Mukhlesur Rahman, Parvin, Ekramul Haque, Ekramul Islam, & Mosaddik, 2005; Pomper, Lowe, Crabtree, & Keller, 2009; Potts et al., 2012; Ye, Alfonso, Evert, & McLaughlin, 1996; G. Zhao, Hui, Rupprecht, McLaughlin, & Wood, 1992; G. X. Zhao, Chao, Zeng, & McLaughlin, 1996; G. X. Zhao, Miesbauer, Smith, & McLaughlin, 1994).
Members of the Ericaceae including Laurels (Kalmia spp.) Pieris (Pieris spp.) and Dog Hobble (Leucothoe spp.) are known to be toxic to livestock. Many Ericaceous plants contain sodium channel inhibitors (Nelson et al., 2007). Poisoning may also occur from the consumption of honey that contains nectar from members of the Ericaceae. However, Doug Elliot (2011) says that honey his bees made from Rhododendron was unusually clear and very bitter thereby precluding ingestion. Carolina Jessamine (Gelsemium sempervirens) in the Loganiaceae is a plant that has been shown to cause toxicity in humans both from flowers and honey containing nectar (Hardin & Arena, 1974).
Some plants that are commonly consumed have poisonous parts. Examples include Elderberry (Sambucus spp.), Pokeweed (Phytolacca americana), Rhubarb (Rheum sp.) and members of the Solanaceae family. A full treatment of poisonous and edible fruits can be referenced for further clarification (Hardin & Arena, 1974).
Food allergies are also common to a subset of people. Plants causing allergies include many nuts, Soybeans (Glycine max), species in the Rosaceae and gluten containing members of Poaceae such as Wheat, Barley, Rye and Spelt. i have also met people occasionally with more rare plant allergies such as Cacao, Ginger, Sesame, Strawberries, Nightshades and others…
One must be careful when analyzing the poisonous potential of plants. The devil is in the details. The poisonous nature of plants is often related to a multitude of factors. The information presented here represents a broad overview simply designed to raise the awareness of potential toxins. Several plants and especially plant families mentioned can represent choice members of a healthy diet. Much toxicological research has also focused on the effect to livestock versus people. It is not possible for me to always differentiate between these two classifications at present. Easy to attain books concerning poisonous effects of plants on humans solely can be referenced for further study on that subject (Alber & Alber, 1993; Dauncey, 2010; Hardin & Arena, 1974; Nelson et al., 2007; Schmutz & Hamilton, 1988; Scott & Thomas, 2000). A treatment of over 1,200 poisonous plants of the world and their relative toxicity may give further insight (Wink & Van Wyk, 2008).
A few books list specifically the poisonous plants of the eastern U.S. (Blackwell, 1990; Pammel, 1911; Westbrooks & Preacher, 1986). A publication detailing the most common plants causing poisoning in the southern United States has also been written listing 56 species and 26 families (Kates, Davis, McCormack, & Miller, 1980). The major families by far followed by number of species listed were the Pea (Fabaceae) (9), Heath (Ericaceae) (8), and Aster (Asteraceae) (6).
A number of texts cover the whole United States and beyond (G. E. Burrows & Tyrl, 2001, 2013; Dauncey & Larsson, 2018; Kinghorn, 1979; Lampe, McCann, & Association, 1985; Leikin & Paloucek, 2007; Tornio, 2017; Wagstaff, 2008).
Regional texts are also available for the following areas listed below:
California (Fuller & McClintock, 1987)
Colorado (Durrell & Newsom, 1939)
Great Britain (Gillam, 2008)
Hawaii (Arnold, 2019; Scott & Thomas, 2000)
Iraq (Al-Rawi, 1988)
Oklahoma (G. Burrows & Tyrl, 1996)
Pennsylvania (Ditmer, 1965; Hill, 1986)
Rhodesia/Tanzania (Shone, 1900) and
South Africa (Wyk, Heerden, & Oudtshoorn, 2002)
Southeast USA (Powe, Jr., Freeman, & Everest, 2005)
Southwest USA (Schmutz & Hamilton, 1988)
A number of resources also cover poisonous plants of Florida and the Caribbean as well (Adams, Magnus, & Seaforth, 1963; Campbell, 1983; Dahlgren, 1944; Lockey, Stewart, & Maxwell, 1992; Lowe, Morrison, Magnus, & Campbell-Grizzle, 2004; Julia Frances Morton, 1971; Nellis, 1997; West, 1984).
Hopefully this overview has given a sense of some of the toxins out there and the major families containing them.
For the next class we will cover major Woody Plant families it will be posted around Imbolc August 2.
Below are items to think about/comment on. Please write me directly at email@example.com or leave information in the commentary under this class.
I WOULD REALLY LOVE TO HEAR WHAT YOU HAVE TO SAY!!!
- Make a list of the poisonous plants around you and share that info with some people.
- Attend a workshop or a class and write up a brief description of plants or information learned.
- Try to make a list of the plants for your county using the USDA website search at www.plants.usda.gov
- Post any clear photos of question plants to Facebook or send in an email.
Praises to all that have donated to the cause. i encourage everyone reading this to donate as they are able financially, commentarially, or energetically... Your contributions greatly help me continue this crucial work of ethnobotanical research and education. Please let me know your thoughts in general and anyway i can help this class serve you best.
Abbe, E. M. (1985). The Fern Herbal: Including the Ferns, the Horsetails, and the Club Mosses. Ithaca: Cornell Univ Press.
Adams, C. D., Magnus, K., & Seaforth, C. (1963). Poisonous Plants in Jamaica. Mona, Jamaica: Dept. of Extra-Mural Studies, University of the West Indies.
Alber, J. I., & Alber, D. M. (1993). Baby-Safe Houseplants & Cut Flowers: A Guide to Keeping Children and Plants Safely Under the Same Roof. Pownal, VT.: Storey Books.
Al-Rawi, A. (1988). Poisonous plants of Iraq (3rd edition). Published by the Ministry of Agriculture & Irrigation of the Republic of Iraq.
Anderson, T. E. (1995). The Poison Ivy, Oak and Sumac Book: A Short Natural History and Cautionary Account. Ukiah, CA: Acton Circle Pub Co.
Araya, H., Sahai, M., Singh, S., Singh, A. K., Yoshida, M., Hara, N., & Fujimoto, Y. (2002). Squamocin-O1 and squamocin-O2, new adjacent bis-tetrahydrofuran acetogenins from the seeds of Annona squamosa. Phytochemistry, 61(8), 999–1004. https://doi.org/10.1016/S0031-9422(02)00351-5
Arnold, H. L. (2019). Poisonous Plants of Hawaii. Independently published.
Biller, A., Boppré, M., Witte, L., & Hartmann, T. (1994). Pyrrolizidine alkaloids in Chromolaena odorata. Chemical and chemoecological aspects. Phytochemistry, 35(3), 615–619. https://doi.org/10.1016/S0031-9422(00)90573-9
Blackwell, W. H. (1990). Poisonous and Medicinal Plants. Englewood Cliffs, NJ: Prentice Hall.
Brown, M. (2018). Death in the garden: Poisonous plants & their use throughout history. Barnsley: Pen & Sword White Owl, an imprint of Pen & Sword Books Ltd.
Bruneton, J., & Hatton, C. K. (2008). Pharmacognosy, phytochemistry, medicinal plants. Londres; New York; Paris; Andover (U.K.): Tec et doc ; Intercept.
Burrows, G. E., & Tyrl, R. J. (2001). Toxic Plants of North America. Ames, IA: Iowa State University Press.
Burrows, G. E., & Tyrl, R. J. (2013). Toxic Plants of North America (2nd ed.). Hoboken: Wiley-Blackwell.
Burrows, G., & Tyrl, R. J. (1996). Toxic Plants of Oklahoma and the Southern Plains (2nd ed.). Oklahoma State University.
Campbell, G. R. (1983). An Illustrated Guide to Some Poisonous Plants and Animals of Florida. Englewood, FL: Pineapple Pr Inc.
Champy, P., Melot, A., Guérineau Eng, V., Gleye, C., Fall, D., Höglinger, G. U., … Hocquemiller, R. (2005). Quantification of acetogenins in Annona muricata linked to atypical parkinsonism in Guadeloupe. Movement Disorders, 20(12), 1629–1633. https://doi.org/10.1002/mds.20632
Chang, C.-K., Chang, K.-S., Lin, Y.-C., Liu, S.-Y., & Chen, C.-Y. (2005). Hairy Root Cultures of Gynostemma pentaphyllum (Thunb.) Makino: A Promising Approach for the Production of Gypenosides as an Alternative of Ginseng Saponins. Biotechnology Letters, 27(16), 1165–1169. https://doi.org/10.1007/s10529-005-8653-7
Cipollini, D., & Gruner, B. (2007). Cyanide in the chemical arsenal of garlic mustard, Alliaria petiolata. Journal of Chemical Ecology, 33(1), 85–94. https://doi.org/10.1007/s10886-006-9205-x
Cooper, M. R., & Johnson, A. W. (1997). Poisonous Plants & Fungi: An Illustrated Guide. London: The Stationery Office/Tso.
Cox, T., & Ruter, J. M. (2013). Landscaping with Conifers and Ginkgo for the Southeast. Gainesville, FL: University Press of Florida.
Crane, P. (2013). Ginkgo: The Tree That Time Forgot. New Haven, CT: Yale University Press.
Cui, J.-F., Eneroth, P., & Bruhn, J. G. (1999). Gynostemma pentaphyllum: Identification of major sapogenins and differentiation from Panax species. European Journal of Pharmaceutical Sciences, 8(3), 187–191. https://doi.org/10.1016/S0928-0987(99)00013-5
Dahlgren, B. E. (1944). Edible and poisonous plants of the Caribbean region. The Supt. of Docs., U.S. G.P.O.
Dauncey, E. A. (2010). Poisonous Plants: A Guide for Parents & Childcare Providers. Kew: Royal Botanic Gardens, Kew.
Dauncey, E. A., & Larsson, S. (2018). Plants That Kill: A Natural History of the World’s Most Poisonous Plants. S.l.: Princeton University Press.
Day, J. (2008). Don’t Touch That!: The Book of Gross, Poisonous, and Downright Icky Plants and Critters. Chicago: Chicago Review Press.
Ditmer, W. P. (1965). Poisonous plants of Pennsylvania. Dept. of Agriculture.
Duke, J. A., & Foster, S. (2014). Peterson Field Guide to Medicinal Plants and Herbs of Eastern and Central North America (3rd Ed). Houghton Mifflin Harcourt.
Durrell, L. W., & Newsom, I. E. (1939). Colorados Poisonous And Injurious Plants Revision Of Bulletin 429, Bulletin 455. Colorado Experiment Station.
Elpel, T. (2013). Botany in a Day: The Patterns Method of Plant Identification. (6th ed.). Pony, MT: HOPS Press, LLC.
Frohne, D., & Pfander, H. J. (2005). Poisonous Plants: A Handbook for Doctors, Pharmacists, Toxicologists, Biologists and Veterinarians (2nd ed.). Portland, OR: Timber Press, Inc.
Fuller, T. C., & McClintock, E. (1987). Poisonous Plants of California. Berkeley: University of California Press.
Ganora, L. (2009). Herbal constituents: Foundations of phytochemistry : a holistic approach for students and practitioners of botanical medicine. Louisville, CO: Herbalchem Press.
Gillam, F. (2008). Poisonous plants in Great Britain. Butleigh: Wooden.
Hardin, J. W., & Arena, J. M. (1974). Human Poisoning from Native and Cultivated Plants (2nd ed). Durham, NC: Duke University Press.
Harper, S. H., Potter, C., & Gillham, (Mrs) E. M. (1947). Annona Species as Insecticides. Annals of Applied Biology, 34(1), 104–112. https://doi.org/10.1111/j.1744-7348.1947.tb06347.x
Hashimoto, K., Higuchi, M., Makino, B., Sakakibara, I., Kubo, M., Komatsu, Y., … Okada, M. (1999). Quantitative analysis of aristolochic acids, toxic compounds, contained in some medicinal plants. Journal of Ethnopharmacology, 64(2), 185–189. https://doi.org/10.1016/S0378-8741(98)00123-8
Hauser, S. C., & Epstein, W. L. (2008). A Field Guide to Poison Ivy, Poison Oak, and Poison Sumac: Prevention and Remedies (3rd ed.). Guilford, CT: FalconGuides.
He, K., Zhao, G.-X., Shi, G., Zeng, L., Chao, J.-F., & McLaughlin, J. L. (1997). Additional bioactive annonaceous acetogenins from Asimina triloba (Annonaceae). Bioorganic & Medicinal Chemistry, 5(3), 501–506. https://doi.org/10.1016/S0968-0896(96)00264-7
Hill, R. J. (1986). Poisonous Plants of Pennsylvania. Harrisburg, PA: Commonwealth of Pennsylvania,.
Kallas, J. (2010). Edible Wild Plants: Wild Foods From Dirt To Plate. Gibbs Smith.
Kates, A. H., Davis, D. E., McCormack, J., & Miller, J. F. (1980). Poisonous Plants of the Southern United States. Raleigh, NC: North Carolina Agricultural Extension Service, North Carolina State University.
Kinghorn, A. D. (Ed.). (1979). Toxic Plants. New York: Columbia University Press.
Kingsbury, J. M. (1964). Poisonous Plants of the United States and Canada. Englewood Cliffs, NJ: Prentice-Hall.
Lampe, K., McCann, M. A., & Association, A. M. (1985). AMA Handbook of Poisonous and Injurious Plants. Chicago, Ill: Amer Medical Assn.
Lannuzel, A., Michel, P. P., Caparros-Lefebvre, D., Abaul, J., Hocquemiller, R., & Ruberg, M. (2002). Toxicity of Annonaceae for dopaminergic neurons: Potential role in atypical parkinsonism in Guadeloupe. Movement Disorders, 17(1), 84–90. https://doi.org/10.1002/mds.1246
Leikin, J. B., & Paloucek, F. P. (Eds.). (2007). Poisoning and Toxicology Handbook (4th ed.). Boca Raton: CRC Press.
Levine, R. A., Richards, K. M., Tran, K., Luo, R., Thomas, A. L., & Smith, R. E. (2015). Determination of Neurotoxic Acetogenins in Pawpaw (Asimina triloba) Fruit by LC-HRMS. Journal of Agricultural and Food Chemistry. https://doi.org/10.1021/jf504500g
Lockey, R. F., Stewart, G. E., & Maxwell, L. S. (1992). Florida’s Poisonous Plants-Snakes-Insects: This book Might Save the Life of One You Love... (Rev). Tampa, FL: Lewis S. Maxwell.
Lowe, H., Morrison, E., Magnus, K., & Campbell-Grizzle, E. (2004). Poisonous Plants of Jamaica: Their Toxins and Treatment. Kingston, Jamaica: Pelican Publishers Ltd.
Malviya, S. M. / S. R. / N. (2015). Textbook of Pharmacognosy and Phytochemistry (1st edition). CBS.
McLaughlin, J. L. (2008). Paw paw and cancer: Annonaceous acetogenins from discovery to commercial products. Journal of Natural Products, 71(7), 1311–1321. https://doi.org/10.1021/np800191t
Morton, Julia F. (n.d.). Lantana, or red sage (Lantana camara L., [Verbenaceae]), notorious weed and popular garden flower; some cases of poisoning in Florida. Economic Botany, 48(3), 259. https://doi.org/10.1007/BF02862327
Morton, Julia Frances. (1971). Plants poisonous to people in Florida and other warm areas. Hurricane House.
Muenscher, W. C. (1940). Poisonous Plants of the United States. New York: MacMillan Publishing Co.
Mukhlesur Rahman, M., Parvin, S., Ekramul Haque, M., Ekramul Islam, M., & Mosaddik, M. A. (2005). Antimicrobial and cytotoxic constituents from the seeds of Annona squamosa. Fitoterapia, 76(5), 484–489. https://doi.org/10.1016/j.fitote.2005.04.002
Nellis, D. W. (1997). Poisonous Plants and Animals of Florida and the Caribbean. Sarasota, FL: Pineapple Press.
Nelson, L. S., Shih, R. D., & Balick, M. J. (2007). Handbook of Poisonous and Injurious Plants (2nd ed.). New York: Springer.
Pammel, L. H. (1911). A Manual of Poisonous Plants. Chiefly of Eastern North America. Cedar Rapids, IA: The Torch Press.
Pomper, K. W., Lowe, J. D., Crabtree, S. B., & Keller, W. (2009). Identification of annonaceous acetogenins in the ripe fruit of the North American pawpaw ( Asimina triloba ). Journal of Agricultural and Food Chemistry, 57(18), 8339–8343. https://doi.org/10.1021/jf9018239
Potts, L. F., Luzzio, F. A., Smith, S. C., Hetman, M., Champy, P., & Litvan, I. (2012). Annonacin in Asimina triloba fruit: Implication for neurotoxicity. Neurotoxicology, 33(1), 53–58. https://doi.org/10.1016/j.neuro.2011.10.009
Pour, B. M., Latha, L. Y., & Sasidharan, S. (2011). Cytotoxicity and Oral Acute Toxicity Studies of Lantana camara Leaf Extract. Molecules, 16(5), 3663–3674. https://doi.org/10.3390/molecules16053663
Pour, B. M., & Sasidharan, S. (2011). In vivo toxicity study of Lantana camara. Asian Pacific Journal of Tropical Biomedicine, 1(3), 230–232. https://doi.org/10.1016/S2221-1691(11)60033-6
Powe, Jr., T. A., Freeman, J. D., & Everest, J. W. (2005). Poisonous Plants of the Southeastern United States (SP 57 / Revised April 2005 edition). University of Florida.
Razmovski-Naumovski, V., Huang, T. H.-W., Tran, V. H., Li, G. Q., Duke, C. C., & Roufogalis, B. D. (2005). Chemistry and Pharmacology of Gynostemma pentaphyllum. Phytochemistry Reviews, 4(2–3), 197–219. https://doi.org/10.1007/s11101-005-3754-4
Rogers, R. D. (2014). Ancient medicinal remedies: Horsetails, ferns, lichens and more.
Schaneberg, B. T., Applequist, W. L., & Khan, I. A. (2002). Determination of aristolochic acid I and II in North American species of Asarum and Aristolochia. Die Pharmazie, 57(10), 686–689.
Schep, L. J., Slaughter, R. J., Becket, G., & Beasley, D. M. G. (2009). Poisoning due to water hemlock. Clinical Toxicology, 47(4), 270–278. https://doi.org/10.1080/15563650902904332
Schlag, E. M., & McIntosh, M. S. (2006). Ginsenoside content and variation among and within American ginseng (Panax quinquefolius L.) populations. Phytochemistry, 67(14), 1510–1519. https://doi.org/10.1016/j.phytochem.2006.05.028
Schmutz, E. M., & Hamilton, L. B. (1988). Plants That Poison: An Illustrated Guide to Plants Poisonous to Man. Flagstaff, AZ: Northland Press.
Scott, S., & Thomas, C. (2000). Poisonous Plants of Paradise: First Aid and Medical Treatment of Injuries from Hawaii’s Plants. Honolulu: University of Hawaii Press.
Sharma, O. P., Makkar, H. P. S., Dawra, R. K., & Negi, S. S. (1981). A Review of the Toxicity of Lantana camara (Linn) in Animals. Clinical Toxicology, 18(9), 1077–1094. https://doi.org/10.3109/15563658108990337
Shone, D. K. & D., R. B. (1900). Poisonous Plants of Rhodesia. Ministry of Agriculture.
Singh, B., Kaur, P., Gopichand, Singh, R. D., & Ahuja, P. S. (2008). Biology and chemistry of Ginkgo biloba. Fitoterapia, 79(6), 401–418. https://doi.org/10.1016/j.fitote.2008.05.007
Stewart, A. (2009). Wicked Plants: The Weed That Killed Lincoln’s Mother and Other Botanical Atrocities. Chapel Hill, NC: Algonquin Books.
Stewart, A. (2016). The Wicked Plants Coloring Book. Algonquin Books.
Stuart, D. C. (2004). Dangerous garden: The quest for plants to change our lives. Cambridge, MA: Harvard University Press.
Tornio, S. (2017). Plants That Can Kill: 101 Toxic Species to Make You Think Twice. Skyhorse Publishing.
Turner, N. J., & Szczawinski, A. F. (1995). Common Poisonous Plants and Mushrooms of North America. Portland, OR: Timber Press.
Turner, Nancy J, & Aderkas, P. von. (2009). The North American guide to common poisonous plants and mushrooms. Portland: Timber Press.
Vetter, J. (2004). Poison hemlock (Conium maculatum L.). Food and Chemical Toxicology, 42(9), 1373–1382. https://doi.org/10.1016/j.fct.2004.04.009
Wagstaff, D. J. (2008). International Poisonous Plants Checklist: An Evidence-Based Reference. Boca Raton: CRC Press.
West, E. (1984). Poisonous plants around the home. Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida.
Westbrooks, R. G., & Preacher, J. W. (1986). Poisonous Plants of Eastern North America (1st ed). Columbia, SC: University of South Carolina Press.
Wink, M., & Van Wyk, B.-E. (2008). Mind-Altering and Poisonous Plants of the World (1st ed). Portland, OR: Timber Press.
Wolfson, S. L., & Solomons, T. G. (1964). Poisoning by fruit of lantana camara: An acute syndrome observed in children following ingestion of the green fruit. American Journal of Diseases of Children, 107(2), 173–176. https://doi.org/10.1001/archpedi.1964.02080060175011
Wyk, B.-E. van, Heerden, F. van, & Oudtshoorn, B. van. (2002). Poisonous Plants of South Africa. Briza.
Ye, Q., Alfonso, D., Evert, D., & McLaughlin, J. L. (1996). Longifolicin, longicoricin, and gigantetroneninone, three novel bioactive mono-tetrahydrofuran annonaceous acetogenins from Asimina longifolia (annonaceae). Bioorganic & Medicinal Chemistry, 4(4), 537–545. https://doi.org/10.1016/0968-0896(96)00039-9
Zhao, G., Hui, Y., Rupprecht, J. K., McLaughlin, J. L., & Wood, K. V. (1992). Additional Bioactive Compounds and Trilobacin, a Novel Highly Cytotoxic Acetogenin, from the Bark of Asimina triloba. Journal of Natural Products, 55(3), 347–356. https://doi.org/10.1021/np50081a011
Zhao, G. X., Chao, J. F., Zeng, L., & McLaughlin, J. L. (1996). (2,4-cis)-asimicinone and (2,4-trans)-asimicinone: Two novel bioactive ketolactone acetogenins from Asimina triloba (Annonaceae). Natural Toxins, 4(3), 128–134.
Zhao, G. X., Miesbauer, L. R., Smith, D. L., & McLaughlin, J. L. (1994). Asimin, asiminacin, and asiminecin: Novel highly cytotoxic asimicin isomers from Asimina triloba. Journal of Medicinal Chemistry, 37(13), 1971–1976.