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Elisabeth C. Miller Library

Keyword: Poisonous plants

Edible flowers for wedding cakes

I am planning to decorate my wedding cake with Alstroemeria. Are these flowers safe to use? The flowers won’t be eaten, but will be in contact with the icing.

 

The website of National Sustainable Agriculture Information Service has a page of resources on edible flowers, including links to information about toxic plants. Alstroemeria can cause contact dermatitis when handled, and ingesting the plant can cause gastrointestinal problems. See the following information on Alstroemeria from North Carolina State University Extension.

Rather than take any chances, I recommend restricting your decoration choices to
edible flowers. A mixture of calendula, lavender, and violet blossoms, for
example, might be an attractive option. North Carolina State University Extension also has an article on edible flowers.

Iowa State University Extension has useful guidelines on selecting edible flowers.

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On the edibility of fiddleheads

Are Bracken fern fiddleheads edible? The very old Euell Gibbons edible plant books say it’s o.k. but I’ve heard rumors that it is toxic and shouldn’t be eaten. Do the edible Ostrich Ferns grow in western Washington? I have lots of sword ferns, but nobody seems to mention if they are edible.

 

The fern whose fiddleheads are most commonly (and perhaps most safely) consumed is the ostrich fern, Matteuccia struthiopteris. According to Sue Olsen’s Encyclopedia of Garden Ferns, this plant will grow “in the severe and forbidding climates of Newfoundland and Alaska,” but they do not do well in areas with hot summers. We do occasionally have hot summers in Washington State, so that could pose a challenge, but if you suite the plant in an area with some shade, it might survive a heat wave.

The University of Maine Extension has a factsheet entitled “Facts on Fiddleheads” which mentions the health risks associated with their consumption, and offers tips on how to avoid illness. Note also, this Centers for Disease Control and Prevention page on Ostrich Fern Poisoning.

An article in Fine Gardening discusses which fern fiddleheads are safe to eat.
Excerpt:
“Throughout the world, several types of fiddleheads are eaten, though most contain toxic compounds. The most commonly eaten and most esteemed fiddlehead is that of the ostrich fern (Matteuccia struthiopteris, USDA Hardiness Zones 2-8), often simply called fiddlehead fern. The ostrich fern is the safest fern to eat, even though it, too, can contain toxins. The fiddleheads of cinnamon fern (Osmunda cinnamomea), lady fern (Athyrium filix-femina), and bracken fern (Pteridium aquilinum) can also be eaten, but all are at least mildly toxic and can cause nausea, dizziness, and headache, so it’s probably best to avoid them. The safest way to eat fiddleheads is to stick to ostrich ferns and to eat them in small quantities.”

Below is information specifically about bracken fern, Pteridium aquilinum.

Handbook of Poisonous and Injurious Plants by Lewis Nelson et al. (New York Botanical Garden, 2007) says that all parts of the plant are toxic. The toxin is thought to be ptaquiloside, a sesquiterpene.

From the Earl J. S. Rook website (no longer available online):
“Most commonly used today as a food for humans. The newly emerging croziers or fiddleheads are picked in spring and may be consumed fresh or preserved by salting, pickling, or sun drying. Both fronds and rhizomes have been used in brewing beer, and rhizome starch has been used as a substitute for arrowroot. Bread can be made out of dried and powered rhizomes alone or with other flour. American Indians cooked the rhizomes, then peeled and ate them or pounded the starchy fiber into flour. In Japan starch from the rhizomes is used to make confections. Bracken fern is grown commercially for use as a food and herbal remedy in Canada, the United States, Siberia, China, Japan, and Brazil and is often listed as an edible wild plant. Powdered rhizome has been considered particularly effective against parasitic worms. American Indians ate raw rhizomes as a remedy for bronchitis.
Bracken fern has been found to be mutagenic and carcinogenic in rats and mice, usually causing stomach or intestinal cancer. It is implicated in some leukemias, bladder cancer, and cancer of the esophagus and stomach in humans. All parts of the plant, including the spores, are carcinogenic, and face masks are recommended for people working in dense bracken. The toxins in bracken fern pass into cow’s milk. The growing tips of the fronds are more carcinogenic than the stalks. If young fronds are boiled under alkaline conditions, they will be safer to eat and less bitter.”

The book Ecosystems and Human Health by Richard Philp (CRC Press, 2001) states that “considerable evidence exists that bracken fern produces bladder cancer in cattle that eat excessive amounts when better fodder is unavailable, and in rats fed large amounts of it. Because the young shoots, called fiddleheads because of their curled shape, are eaten as a delicacy in many parts of the world, including Canada and Japan, there has been concern over potential for carcinogenic effects in humans. At one point, it was suggested that the relatively high incidence of bladder cancer in Japan might be related to consumption of bracken fern. Epidemiological studies, however, have failed to demonstrate such an association, and it is now felt that eating fiddleheads does not constitute a risk factor for cancer.”

This Northwest gardener, Paghat, also discusses the toxicity and edibility of bracken fern:

Excerpt:

“While causality for human illness from eating bracken is not proven, plausibility is present. Toxins break down in cooking, but the traditional light frying or quick parboiling is insufficient to break down potentially harmful chemical components. Bracken should be cooked at high temperatures to be safe, and are quite easy to prepare correctly in woks.

It is not recommended to eat rare bracken under any circumstances because of the statistical increase in cancers in countries where brackens are a consumed in high numbers. Ostrich Ferns are of such low toxicity as to be far preferable to meet the dietary interest in fiddleheads. But as a well-cooked food item eaten only occasionally, there is no indication of risk from bracken. Plausible risk is restricted to the accumulative effects over time from consumptions of high amounts of bracken parboiled or so briefly cooked as to still contain toxins.”

Sword fern (Polystichum munitum) growing in the wild is seldom browsed by herbivorous animals because the rough foliage is fairly repellent. That specific epithet ‘munitum’ in the scientific name means ‘armed.’ You may have seen information about Native Americans roasting the rhizomes and eating them, but this was a famine food resorted to when other resources were scarce. (The leaves were used to line fire pits for cooking, according to Frank Tozer’s book, The Uses of Wild Plants, 2007). I would not take unnecessary risks experimenting with plants that are not typically considered edible.

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Toxicity of Nandina berries to birds

A rumor has been circulating among birders in our area (Puget Sound) regarding the toxicity of nandina berries to birds, specifically cedar waxwings. I use a fair amount of nandina in my landscape designs, so this is obviously a concern.

How toxic are nandina berries for wildlife? How often do birds or other critters eat enough of the fruit to be damaging?

 

I think that people are probably referring to this study:

Excerpt:
“Nandina domestica berries contain cyanide and other alkaloids. For most cultivars of N. domestica, cyanogenesis is the most important intoxication factor. Cyanide glycosides are substances present in many plants that can produce highly toxic hydrogen cyanide (HCN). At least 2000 plant species are known to contain cyanide glycosides with the potential to produce HCN poisoning. Generally, most parts of the plants contain cyanogenic glycocides [sic], the young rapidly growing portion of the plant and the seeds containing the highest concentration. At least 55 cyanogenic glycosides are known to occur in plants, many being synthesized from aminoacids as part of normal plant metabolism. Frost and drought conditions may increase cyanogenesis in some plant species. Cool moist growing conditions enhance the conversion of nitrate to aminoacids and cyanogenic glycosides instead of plant protein. Presumably, similar weather conditions during late winter and early spring in the study area might have favored increased cyanogenesis in N. domestica.”

Note that this is the first time a mass death of waxwings has been observed, studied, and related to Nandina. Also note that Nandina is invasive in southern states (which means there is probably a lot of it in Georgia, where the deaths were noticed). If there are diverse food sources for the birds in the landscapes you design, perhaps consumption of a few Nandina berries is less of an issue. Another thing to note is that there are a great many other plants whose fruit contains cyanogenic glycosides, and we are unlikely to be able to avoid planting every single genus with this characteristic.

You could aim to plant several plants in each landscape you create which are the preferred diet of local birds. Here is information about the cedar waxwing’s feeding habits.
Excerpt:

“Cedar Waxwings feed mainly on fruits year-round. In summer, they feed on fruits such as serviceberry, strawberry, mulberry, dogwood, and raspberries. The birds name derives from their appetite for cedar berries in winter; they also eat mistletoe, madrone, juniper, mountain ash, honeysuckle, crabapple, hawthorn, and Russian olive fruits. In summer Cedar Waxwings supplement their fruit diet with protein-rich insects including mayflies, dragonflies, and stoneflies, often caught on the wing. They also pick items such as scale insects, spruce budworm, and leaf beetles directly from vegetation.”

The rumor continues to arise from time to time, because of social media. This article by Mike Darcy, from the April 2014 issue of Digger, is helpful. In it, he quotes Nikkie West, the backyard habitat coordinator for Audubon in Portland, Oregon:
“We have not taken in any birds at the Wildlife Care Center that have displayed the symptoms associated with the Nandina berry, nor have our wildlife veterinarians heard about the issue within rehabilitation circles and professional affiliations in the Pacific Northwest. […] Of the approximately 3,000 birds we take in at the Audubon Wildlife Care Center each year, domestic house cats are by far the largest cause of injuries — about 40 percent. Due to the types of injuries sustained, these birds
have a low survival rate.”

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Is it a crocus?

I just discovered a flower growing in my garden this fall. It looks very much like a large pink crocus. Someone told me it is called naked ladies. Is it actually a crocus? Is it poisonous?

 

Here is the tricky thing about common names: they often refer to more than one plant. Based on your description of a low-growing flower like a crocus, it sounds like Colchicum autumnale is growing in your garden. If it had long bare stems and lily-like flowers, you would be looking at naked ladies of another sort, that is, Amaryllis belladonna, or possibly a species of Lycoris (both of which are in the Amaryllis family). What they all share is the characteristic of flowering once the foliage has died back (hence the nakedness of a flower without leaves).

Colchicum is in the family Colchicaceae. It has a history of being misidentified as Crocus sativus, the source of saffron, which also flowers in fall. Crocuses belong to a different family, the Iridaceae. Mistaking Colchicum (also called meadow saffron, which adds to the confusion) with Crocus sativus (whose dried orange stigmas have culinary and medicinal uses) can have dire consequences. When the 17th century herbalist Nicholas Culpeper cautioned that “some have fallen into an immoderate convulsive laughter which ended in death” from consuming saffron, it is likely that people had ingested Colchicum stigmas, not saffron from crocuses. Colchicine (which is sometimes used as a gout medication) is highly toxic when ingested. Amaryllis belladonna and Lycoris are also toxic, especially to cats and dogs, but humans should not ingest any part of these plants, either.

Naked ladies were once naked boys, the prevailing common name before Victorian morality intervened and thought it too suggestive. Why ‘naked ladies’ is any less so is a mystery. It is not known who coined the name ‘naked boys,’ but an early flora of Nottingham by George Charles Deering (an 18th century German-born botanist and physician) documents their presence in the autumn garden. The name is thought to go back as far as the 16th century.

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Brugmansia and the “Devil’s Breath”

I know that Brugmansia has toxic and intoxicating properties. I heard a story about a railway carriage in Europe that was filled with the Brugmansia flowers. When the doors to the carriage were closed, the fragrance of the blooms caused the passengers to lose consciousness, and their valuables were stolen. Plausible, or urban legend?

Brugmansia, like the related solanaceous plant Datura, contains tropane alkaloids throughout the plant, including the seeds and flowers. One of these alkaloids is scopolamine. There are many tales of “Devil’s Breath,” a processed form of scopolamine (as powder), or scopolamine-rich seeds being used by criminals in various parts of the world to drug their victims into unconsciousness. There is an article in The Guardian (September 2, 2015) which suggests it’s unlikely that this substance would have been used to “zombify” travelers in Europe. There are, however, travel security warnings from the U.S. State Department about its use by criminals in Ecuador and Colombia.

A scientific article, “Volatile compounds emitted from flowers and leaves of Brugmansia X candida (Solanaceae)” (G.C. Kite and C. Leon, in Phytochemistry, 1995) states that volatile tropane alkaloids could not be detected in the fragrance of either flowers or leaves; the main volatile organic compounds emitted by the flowers are terpenoids, benzenoids, and indole. Those compounds can cause headaches but it seems unlikely they would act like a sedative.

The book Plant Intoxicants by Baron Ernst von Bibra (Healing Arts Press,1995) describes use of Datura seeds by criminals in India to knock out their victims. There are many traditional medicinal uses of Brugmansia among the indigenous tribes of Colombia, but the hallucinogenic effects are especially frightening. One tribe describes the pleasant scent of the flowers but warns that the plant is inhabited by an evil spirit and all who sit at the foot of the tree “will forget everything.” (Source: Plants of the Gods, Richard Evans Schultes, Healing Arts Press, 2001). However I cannot find any confirmation for your colorful story of a train carriage full of drugged passengers among the Brugmansia flowers.

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Growing rhubarb with other edible plants

I just moved into a house with a beautiful vegetable garden with lettuce, kale, arugula and rhubarb (planted next to the lettuce). We have a 7-month old who will likely be all over the back yard in the next few months, and we have a few concerns about the rhubarb leaves, as we’ve heard they are poisonous.

Could rainwater roll off the rhubarb leaves and contaminate the lettuce? Could leaves left on the ground contaminate the soil? And if we touch the leaves, will the rhubarb’s poisonous properties contaminate our hands?

We aren’t huge rhubarb fans, so we will likely be taking them out at the end of this summer. Any tips on removing them to make sure they would not grow back?

Lastly, unrelated to rhubarb, we have some arugula that’s bolted (flowered). Is there anything we can do, like cutting it back, so it won’t be bitter and we can eat it? I assume we have to just replant it.

The toxic parts of rhubarb (Rheum x hybridum) are the leaves and the roots, as described by University of Illinois Extension:

“One characteristic consistent with all rhubarb is the toxicity of the leaves and roots. The rhubarb leaves contain high amounts of oxalic acid, a toxic and potentially deadly poison.”

Rhubarb is a frequently grown vegetable garden plant, and is often grown in close quarters (in the same soil, with the same irrigation) with other edible plants. As long as you are careful when harvesting your lettuce not to get pieces of rhubarb leaf at the same time, you should be safe. Here is what Plant Alert: A Garden Guide for Parents by Catherine Collins (Master Craftsman, 2001) says: “The leaf blade contains high concentrations of oxalic acid […] The stem is safe to eat, providing the leaf is removed with at least 2 inches of stalk below.” (By the way, rhubarb stalks or stems, spinach, beet greens, and chard all contain lesser amounts of oxalic acid–that’s what gives the chalky sensation you get on your teeth sometimes when you eat them.)

You will not be affected by the plant’s leaves or roots unless you ingest them.

There aren’t any special precautions you need to take in order to dig up your rhubarb, although gloves are always a good idea–you never know if your skin may be sensitive to particular plants.

About your arugula (Eruca vesicaria ssp. sativa): I usually cut the bolting stalks back, and new (and less bitter) leaves grow lower down on the plant. You could let one or two plants flower and go to seed–then you wouldn’t need to buy more seed. If you still have extra seed, you can sow more (called “succession planting,” described in this Fine Gardening article), in addition to cutting back the leggy stalks.

Toxic plants lists

We are a fairly young landscape design company, and we are trying to come up with a protocol for dealing with projects that include families with children who want to plant non-toxic plants. In doing some research on the topic, we have discovered that the definition of “toxic” can vary. Some toxic plant lists include plants that others do not, and different kids are allergic to different plants, etc., so we are trying to come up with the best way to handle these types of projects and the best information to give those clients. It seems that these lists can be fairly extensive, leaving us to wonder what is left to plant that is COMPLETELY safe?!

This has been an issue of concern for me as well, as I supervise volunteers in planting and maintaining a school garden. Concerns often arise about toxic plants, some founded and some not. For instance, playground supervisors “erred on the side of caution” (and hysteria) by warning students that our evergreen huckleberries and saskatoons, carefully chosen for their edibility, were “poison berries,” while some parents expressed concern about foxgloves that reseeded from neighboring gardens, knowing that they are toxic. A common sense approach seems to work best. It is easy enough to exclude the plants which seem most likely to cause problems, such as nightshade, yew (the lantern-like berries are attractive and toxic), vetch, sweet pea (the seed pods resemble peas but the seeds are not edible), castor bean, and digitalis from your garden plans, while encouraging parents to supervise their children and provide some edible plants (mint, chives, raspberries, etc.) that children can easily identify and enjoy eating. Toxic plants such as daffodils and rhododendrons seem to me less likely to cause problems because children are not likely to eat them.

We have a good book on this topic, Plants for Play by Robin C. Moore. He points out that the age of the children is an important consideration in choosing which plants to omit. Where babies and toddlers will play, it’s important to “avoid placing highly toxic plants, particularly plants with poisonous fruits and plants that can cause dermatitis, within reach of these age groups.” He also says, under the heading of Educational Benefits, “children will come across poisonous plants at some point during their childhood. If they are unaware of what those plants look like and the dangers they represent, there is a greater possibility that they may expose themselves to those dangers.” Education of the individual child and early supervision are really key.

Our State Poison Control agency has the following fact sheet on this issue. They also keep statistics about which toxic substances cause the most problems locally (plants are not high on most lists). I understand that actual deaths from toxic plants are extremely rare (“It is very rare for plants to cause life-threatening symptoms,” as the fact sheet says), but the worry is something one wants to eliminate.

woodbine toxicity

Are the berries of wild woodbine poisonous?

 

Wild woodbine or woodbine is Lonicera periclymenum. But many species of Lonicera are found in the United States.

For photos of L. periclymenum, see the two sites below:
West Highland Flora
Paghat’s Garden

North Carolina University’s poisonous plant website indicates that the berries of Japanese honeysuckle (Lonicera japonica) are poisonous.

Toxic Plants of North America (G.E. Burrows and R.J. Tyrl, 2001, pp.321, 322) says that while some species of Lonicera (i.e., L. involucrata) are edible, the rest are associated with digestive tract problems in children (nausea, vomiting, diarrhea), especially the European species. In the U.S., on the other hand, records of complaints are not often associated with records of clinical signs.

plants toxic to livestock

Could you recommend some good references with information about plants that are toxic to livestock, particularly to horses?

 

There are a number of resources which list plants that are toxic to animals, and specifically to horses. As you check the lists, keep in mind that just because a plant is not on the toxic list, one cannot assume it is non-toxic.

Here are links to some useful lists:

ASPCA Lists of Plants:

Nontoxic to Animals

Toxic to Horses

Cornell University Department of Animal Science: Plants Poisonous to Livestock (search by affected animal species)

Selected Poisonous Plants of the Pacific Northwest toxic to livestock, from Washington State University

Dr. Duke’s Phytochemical and Ethnobotanical Databases, from
Agricultural Research Service: try searching by plant name. Highly technical, but shows what the active chemical properties are in various plants.

Reprint from Trailblazers magazine

Ten most poisonous plants affecting horses, from the editors of Equus magazine

The Miller Library also has the booklet entitled Commonly Cultivated and Native Oregon Plants Toxic to Domesticated Animals by La Rea Dennis et al., Pacific Western Research, 1990. It is organized by plant family, not by affected animals.

on the toxicity of Azaleas to cats

Are azaleas poisonous to cats?

Azaleas are indeed a problem for cats and other pets. See this link from Purdue University’s Veterinary Program.

Excerpt:
“These ornamental shrubs aren’t commonly nibbled on but they can cause fatal heart problems in dogs, cats, and pet birds. Signs to watch for are similar to that of the yews and include weakness, fainting, salivation, difficulty breathing, vomiting, and diarrhea.”

According to the Handbook of Poisonous and Injurious Plants, 2nd ed., by Lewis Nelson et al. (New York Botanical Garden/Springer, 2007), all Rhododendron species, including Azaleas, contain grayanotoxins in their leaves. Honey made from the flower nectar would also be toxic.