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Search Results for ' Poisonous plants'

PAL Questions: 13 - Garden Tools: - Recommended Websites: 1

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Keywords: Taxus brevifolia, Poisonous plants

PAL Question:

Is our native yew tree poisonous?

View Answer:

Taxus brevifolia, Pacific or Western yew, is native here. The Sunset Western Garden Book (2001, p.628) says that Taxus fruit, seeds, and foliage are poisonous if ingested.

Plants of the Pacific Northwest Coast by Pojar and Mackinnon (Lone Pine, 2004) says that "Western yew seeds are poisonous and humans should avoid the fleshy 'berries,' although a wide variety of birds consume them and disperse the seeds. The foliage is poisonous to horses and cattle."

The Plants for a Future database has more information at this link.

Season All Season
Date 2008-01-03
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Keywords: Poisonous plants, Ilex

PAL Question:

Is a holly tree toxic to animals (dogs/cats)?

View Answer:

The ASPCA website on plants which are toxic to animals lists holly (Ilex spp.), as does the Humane Society website.

According to Plant Alert, A Garden Guide for Parents (by Catherine Collins; 2001), and Plants That Poison (by Ervin M. Schmutz and Lucretia Breazeale Hamilton; 1979) the red or black berries on holly are poisonous to humans as well, and can be fatal to small children if eaten in quantity.

If you believe your dog or cat has consumed holly berries, call your veterinarian for advice as soon as possible, or call the ASPCA Animal Poison Control number, 888-426-4435 (not a free service).

Season All Season
Date 2006-03-06
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Keywords: Lonicera, Poisonous plants, Berries

PAL Question:

Are the berries of wild woodbine poisonous?

View Answer:

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.

Season All Season
Date 2006-12-08
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Keywords: Poisonous plants, Animals

PAL Question:

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

View Answer:

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)

Western Washington plants toxic to horses, from Oregon State University (includes probable toxic dose, toxin, symptoms)

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

Samuel Roberts Noble Foundation - Horse forage

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.

Season All Season
Date 2008-02-07
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Keywords: Zamia, Poisonous plants, House plants, Cycads

PAL Question:

I am interested in finding out if someone there can tell me the proper culture for Zamia furfuracea. I just acquired one that had been potted up as a bonsai and put on sale at a local grocery store. I think they may not have known or cared what it was. This is a plant I grew outdoors when I lived in California. I'm wondering what to do with it in Vancouver, WA. The options are greenhouse, patio pot, indoors, outdoors.

View Answer:

I found general cultural information from Florida State University Cooperative Extension. This is a zone 9b-11 plant, and your area is probably about zone 8, so I think you would want to grow this with some protection.

University of British Columbia Botanical Garden's discussion forum describes this as an indoor plant. This article in the journal of University of Arizona Cooperative Extension is about a similar plant, Zamioculcas zamiifolia, often confused with Zamia furfuracea.

Richard Langer's book, Grow It Indoors (Stackpole Books, 1995) says to grow this "handy table-sized cycad" in temperate partial sun with humusy soil that is kept constantly moist.

Another thing to keep in mind if you are growing this plant around pets or small children is its toxicity. The ASPCA lists this plant as toxic. Dr. Nelson's Veterinary Blog has an article entitled "Sago palms are poisonous to animals."

Season All Season
Date 2007-06-08
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Keywords: Alstroemeria, Poisonous plants, Edible flowers

PAL Question:

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.

View Answer:

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.

Season All Season
Date 2007-07-18
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Keywords: Matteuccia, Pteridium aquilinum, Edible wild plants, Poisonous plants

PAL Question:

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. Also, do the edible Ostrich Ferns grow in the Sultan, WA area?

View Answer:

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. I imagine you would have little difficulty growing this type of fern in your area.

Here is an article from Edible Toronto about culinary use of fiddleheads. 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 Har≠diness 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:
"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."

Season All Season
Date 2009-05-01
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Keywords: Poisonous plants, Children's gardens

PAL Question:

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?!

View Answer:

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.

Season All Season
Date 2009-05-06
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Keywords: Rhododendron, Poisonous plants, Pets

PAL Question:

Are azaleas poisonous to cats?

View Answer:

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.

Season All Season
Date 2011-02-18
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Keywords: Eruca vesicaria ssp. sativa, Rheum x hybridum, Poisonous plants

PAL Question:

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.

View Answer:

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 Organic Gardening article), in addition to cutting back the leggy stalks.

Season All Season
Date 2011-06-11
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Keywords: Aquilegia, Edible wild plants, Poisonous plants, Edible landscaping

PAL Question:

I've been reading up on permaculture and exploring the edibility of common ornamental plants. Several books I've looked at suggest that columbine flowers (Aquilegia canadensis and Aquilegia vulgaris, specifically) are edible. I have my doubts, since columbine is in the family Ranunculaceae, which I would generally consider poisonous. What do you think?

View Answer:

I think you are right to question your sources. Although some species of Aquilegia have ethnobotanical uses as food, you should still proceed with caution. I found information about edible and medicinal uses of Aquilegia formosa. Daniel Moerman's Native American Food Plants, Timber Press, 2010, mentions that the Miwok boiled and ate the early spring greens, and that children of the Hanaksiala tribe sucked nectar from the flowers. In her book Ethnobotany of Western Washington (University of Washington, 1979), Erna Gunther mentions medicinal and edible uses of this species of columbine. The Quileute tribe used the sap to aid in healing wounds, and Chehalis children sucked "honey out of the flowers." However, The North American Guide to Common Poisonous Plants and Mushrooms by Nancy Turner and Patrick von Aderkas (Timber Press, 2009) lists Aquilegia species as toxic:
"Most [members of the Ranunculaceae] contain irritant protoanemonins; columbines contain cyanogenic glycosides."

Columbine is included in University of Vermont Extension's list of "Potentially Harmful Perennials." St. Olaf College's page on wild columbine points out a common confusion between the blossoms of honeysuckle and columbine:
"Young children often mistake Columbine for Honeysuckle, pulling off the flowers and biting the spurs in search of nectar. Though no official records of toxicity have been reported for Columbine, it belongs to a family which contains other toxic species. Caution is advised."

The Plants for a Future database of edible and medicinal plants lists a number of species of columbine. Here is their page on Aquilegia canadensis. I don't find myself convinced by the statement that "the flowers are probably perfectly safe to eat." The entry for Aquilegia vulgaris says that the flowers are "rich in nectar, they are sweet and delightful, they make a very attractive addition to mixed salads and can also be used as a thirst-quenching munch in the garden. The flowers are also used as a tea substitute." It is worth looking at the sources cited at the end of this entry, to decide if you feel they are trustworthy. To summarize, when in doubt, don't eat the columbines (or any other plant whose edibility is debatable)!

Season All Season
Date 2011-12-30
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Keywords: Gardening to attract birds, Nandina domestica, Poisonous plants

PAL Question:

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?

View Answer:

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, 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 birdsí 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."

Season All Season
Date 2013-08-27
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Keywords: Euphorbia pulcherrima, Poisonous plants

PAL Question:

Just how poisonous are poinsettias? My mother lives in a nursing home, and the director just confiscated nearly 200 potted plants that were donated to residents for the holidays. I think he overreacted. Do you agree?

View Answer:

I agree with you. It is a fact that poinsettias (Euphorbia pulcherrima) are in the Euphorbiaceae family, and the sap of plants in this family is irritating to the skin and eyes. However, it seems highly unlikely that people would be exposed to the sap of these plants, and it would take eating large quantities of leaves to become seriously ill. It's not a good idea to eat the leaves of most indoor plants, in any case.

There is information about the degree to which poinsettias are poisonous on the following sites:

It's possible the director of the nursing home was alarmed by a recent news story about a local woman who went to the emergency room after weeding in her garden and getting Euphorbia sap in her eye. There is a big difference between stationary houseplants which one mainly looks at without touching, and the aggressive and weedy Euphorbia species one pulls from the garden (only with gloves and goggles)!

Season Winter
Date 2014-12-13
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December 12 2014 11:33:49