Plants, Toxic to Dogs

Disease of Alimentary System

There are approximately 700 species of poisonous plants in this hemisphere alone. The number of toxic compounds is vast, and the variability of many factors makes the topic of plant poisioning almost overwhelming. For example, toxicity may depend on the soil nourishing the plant, the stage of growth of the plant, the part of the plant, even the sex of the plant, and of course the amount needed for serious symptoms or death. Many plants merely cause dermatis, usually in humans : poison ivy, spurges (Euphorbia spp ) lady’s slippers, and primrose, to name a few. Many others affect only grazing animals and must be eaten in large quantities before poisoning takes place. Dogs are not apt to do extended grazing. Nor would they eat enough of the kind of plant which causes the strange phenomenon of photosensitization. (A few plants when ingested under certain conditions cause a strong reaction to sunlight.) Therefore, in compiling this list of plants potentially harmful to dogs, included will be just those plants grown around the average house or yard and certain wild plants which require only small doses for serious or fatal results. It must be stated that most literature on this topic refers to human, farm stock or laboratory animal poisonings. Few reports of dogs are mentioned, probably for many reasons, incidence not necessarily one of them. Nonetheless, the toxic properties of the plants remain as a potential threat to all, and the back- bone of this list is form a small animal veterinary publication. The use of scientific latin names is necessary for clarification because often several plants are called by the same common name. Actual poisoning compounds, symptoms and treatment the scope of this article. Poisonous plants of the flower garden include some members of the lily and amaryllis families. The bulbs are the dangerous part of hyacinth, narcissus and daffodil, the latter being particularly noxious; also climbing or glory lily (Glariosa superba), some amaryllis, crinum, squill, fritillaria, snowdrops and nerine. Similarly, autumn crocus (Colchicum autumnale) and star-of-Behtlehem bulbs are both very poisonous, Just a moderate amount of the leaves of lily-of-the-valley is enough for serious upset. Aconite or monkshood has exceddingly poisonous herbage and roots. Larkspurs (Delphinium spp.) are a bane of western cattle, and our garden varieties are also suspect. Bastisia or false indigo and lupines fail into this same category. The leaves and roots of the Christmas rose (Helleborus niger) are very troublesome, and the rhizomes of vvhile and cultivated iris cause severe if not serious upset. Foxglove (Digitalis purpurea) is the source of a beneficial heart medicine, but ingesting the fresh plant is dangerous. Other questionable garden flowers are the (Rudebeckia spp.) such as the black-eyed susan, goldenglow and cornflower. (Lobelia spp.) nicotiana or flowering tobacco, poppies, sweet pea, lantana, and bleeding heart (Dicentra spp.) Oleander (Nerium oleander) and poinsettia are so dangerous that a single leaf can be a lethal dose for a child. Meat skewered on oleander branches has killed many humans. Poinsettia like its relatives the spurgues (Euphorbia spp. pencil tree, crown-of-thorns, snow-on-the-mountain, candelabra cactus) has an acrid, burning juice that not only causes dermatitis in humans, but also severely injures the digestive system if chewed.
Dumbcane (Dieffenbachia) and other house plants of the arum family such as caladiurn, alocasia wild calia, elephant ear, some philodendrons and skunk cabbage contain small, sharp crystals of calcium oxalate. Bitting these plants imbeds the crystals in the mouth with resulting pain. Occasionally death follows if swelling at the back of the tongue prevents breathing. The rosary pea or precatory bean seeds and castor bean seeds are deadly just one will kill. The former is shining red and black bean frequently made into jewelry imported from south of the border. Mistletoe and Jerusalem cherry fruits are quite poisonous. The be- still tree or yellow oleander (Thevetia) and the southeast’s tung tree (Aleurites) have lethal nuts. Chinaberry tree (Melia azedarach) berries and even some varieties of avocado leaves, bark and seeds have proved poisionus, as have poinciana pods and yellow or Carolina Jessamine (Gelsemium) flowers, leaves and roots, The vegetable garden has its hazards also. Oddly enough the potato (Solanurn tuberosum) is related to the black nightshade (Solanum nigrurn) which contains poisons in the vines and leaves. There is consequent danger in eating potato eyes and green sunburn spots! Rhubard leaves are very toxic to man and animal. A form of cyanide is found in the seeds of apple and the wilted leaves and seeds of wild and cultivated cherries, peach and aqriect; so an overdose can be unfortunate. The most dangerous ornamental plant is daphne. Although the leaves and bark are poisonous, just a few of the attractive berries can kill a child. Wisteria and goldenchain (Laburnum anagyroides) produce pods with seeds which have led to hosptalization. Mountain laurel, rhododendron. pieris (Pieris japonica), some euonymous, and leucothoe all have leaves and bark which have poisoned cattle and even zoo animals whose cages have been “landscaped”. Privet berries and hydrangea bushes have caused trouble. Box (Buxus sempervirens) clippings are particularly lethal. Yew (Taxus spp.) branches, bark, roots and seeds are often the cause of death, but fortunately the red berries are fairly harmless. The buckeyes, plants or nuts, and the horse chestnut seeds cause illness. Black locust bark, sprouts and seeds and elderberry roots and stems-not ripe berries! -have been found poisonous, Even English ivy (Hedera helix) leaves and berries cause severe symptoms and occassional dermatitis.
Of the multitude of plants beyond our dooryard relatively few highly potent species are liable to endanger a dog. Dutchman”s breeches and squirrel corn, close relatives of bleeding heart,. could cause damage. Jack-in-the-pulpit root contains calcium oxalate crystals. Beneberries or doll’s eyes, cowslip or marsh marigold, some buttercups, and spurges (Euphorbia spp.) contain irritant sap. Mayapple root but not the fruit causes severe digestive upset. Many of the milkweeds are poisonous although very distasteful. The seeds and seedlings of the cocklebur (Xanthium strumarium) are quite dangerous, while the mature plant is evidently harmless. Somewhat confusing but notorious is the trio of water hemlock (Cicuta maculata) poison hemlock (Conium rnaculatum) and ground hemlock (Taxus canadensis). The latter is an American yew which grows wild. Water hemlock is found in swarnpy, moist places. The root, which looks a little like dahlia tubers, and the young shoots are violently poisonous. Poison hemlock is quite similar to Queen Anne’s lace or wild carrot. All of this common plant is deadly, in fact it was the cause of Socrates’ demise. The well-known hemlock tree (Tsuga canaderisis) is entirely unrelated and non-toxic. All members of the nightshade family, including henbane and jimsonweed or thornapple, are most deadly. The latter frequently grows in barnyards or suburban vacant lots. The leaves and seeds of corncockle, bouncing bet, and cow cockle eaten in mederate amojnts are dangerous. False hellebore (Veratrum viride), horsetail, bracken and sensitive ferns also should be mentioned as potential poisoners. The whole plant of the death camas (Zygadenus) is treacherous, especially the bulb which is easily uprooted. Celandine poppy, pokeweed roots, grape-like moonseed fruit, and appropriately dogbane are additional problems, but they are rarely eaten, No list of plants would be complete without mentioning the fungus tribe. Of the lower forma, occasionally favourable conditions produce a accumulation of highly toxic pond scum (algae). When the water becomes paint-like with countless, just visible blue-green particles, animals can be badly poisoned. Only an expert can safely identify edible and inedible mushrooms. Volumes have been written on this subject. However, it is wise to know of the two most common deadly ones, the fly agaric (Amanita musearia) and the destroying angel (Amanita phalloide). A combination of while gills, a bulbous swelling at the bottom, and a veil or ragged skirt around the stem are hallmarks of the Amanitas. Once aware of this formidable array of dangerous plants one can easily fear to venture forth. Odviously, no one Is going to spade over his flower beds, rip out foundation plantings and steer clear of the woods. Yet it may be valuable to recognize which plants to snatch away from inquisitive puppy jaws. If actual poisoning is suspected, a veterinarian can be helped immensely if the plant involed can be identified. All veterinarians cannot be expected to be botanists, and proper diagnosis and treatment for a specific plant poisoning is just as close as the nearest, country-wide Poison Control Centre. Perhaps a life can be saved by foreknowledge of these potentially poisonous plants.

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