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I am often asked about toxic plants and what plants are pet safe. I always flash back to my elementary school in Kemah which was surrounded by huge hedges of oleanders. We kids knew not to eat them. In fact, we knew not to eat anything unless our Moms said it was all right. We didn’t go around chewing on the shrubs. 

Flash forward to horticulture lab in graduate school and the teaching assistant warning everyone to not eat the bean pods of the Texas mountain laurel (Sophora secundiflora) because they had powerful psychotropic properties. 

Oleanders

Nerium oleander is a beautiful, tough, low maintenance tropical shrub. It’s originally from northern Africa, the Arabian peninsula and southern China. Oleanders have been flourishing here, especially in Galveston, Texas, The Oleander City since 1841, when they were first brought to the island from Jamaica by Joseph Osterman. Pretty, but pretty toxic. All parts of the plant are poisonous. 

What makes the oleander toxic? 

Oleanders contain cardenolide glycosides. According to the NIH, the specific poisonous ingredients are digitoxigenin, neriin, oleandrin, and oleondroside. Possible clinical effects include blurred vision, rash, nausea, vomiting, abdominal pain and as one source puts it “bowel evacuation”. Neurological effects are tremor, drowsiness and lack of muscle control. The cardiovascular symptoms of oleander poisoning are particularly dangerous. Depending on how much is ingested, the toxins in oleander will cause rapid heartbeat (tachycardia) and irregular and uncoordinated contraction of the cardiac muscle (fibrillation) leading to cardiac arrest.

Sago Palms and Stone Fruits

Oleander sap is very bitter, like rotten lemons, according to the International Oleander Society. However, you can’t count on something tasting bad to warn off children or pets. Sago palm seeds, which are the most poisonous part of the plant, are quite palatable to dogs and they have a completely different effect. Ingestion of cycasin, the toxin in the seeds, can cause bleeding and bruising due to slowed blood clotting. Within 24 to 48 hours there may be severe liver damage, probably fatal in the long term. 

Contrary to popular belief, the seeds of stone fruits such as cherries, plums, peaches and apricots do not contain cyanide as such. They do contain a cyanogenic glycoside, specifically amygdalin, which is concentrated in the kernels within the fruit pits. Digestive system enzymes will over a few hours, if these kernels are chewed or eaten, transform the cyanogenic glycoside into cyanide, which is of course, poisonous. According to the Canadian Food Inspection Agency, a lethal dose of cyanide is 0.5 to 3.0 mg per kilogram of body weight or about 13 to 15 raw peach pit kernels for an adult. Only 15% of that amount, say two, could be fatal for a child. Cyanide kills by blocking the ability of cells to use oxygen. One of the characteristic signs of cyanide poisoning is the presence of bright pink mucous membranes; abundantly oxygenated blood has no cells taking up the oxygen. Cells rapidly die resulting in cardiac arrest, coma, and death, essentially by the same mechanism as suffocation

A plant with a descriptive name

Yaupon holly (Ilex vomitoria) is native to the southeastern United States. In spite of their reputation, hollies aren't particularly poisonous. The Yaupon does contain a significant amount of caffeine and antioxidants and the leaves have been used by Native Americans for centuries to make a type of tea (black drink). They also held male-only purification rituals which involved fasting and ingesting great quantities of a much stronger version of the drink, throwing up, or who could keep from throwing up the longest. Some things never change.

The truth about poinsettias

Traditional Christmas flower poinsettias (Euphorbia pulcherrima) have a poisonous reputation, but in reality are not particularly toxic. The average person would have to eat 500 to 700 leaves or a 50 pound child would have to eat 500 leaves before any harmful effect and the leaves taste terrible. The sap, however, may cause skin irritation for those with latex allergy as latex and poinsettias share several proteins. 

Sources of information for this post:
www.inchem.org

www.oleander.org

http://999ktdy.com/sago-palms-very-poisonous-to-dogs-cats-humans/

www.nlm.nih.gov/medlineplus/ency/article/002884.htm

http://maxshouse.com/ToxicPlantsComplete.htm#Caesalpinia%20spp

http://www.rightdiagnosis.com/p/plant_poisoning_cyanogenic_glycoside/intro.htm

http://www.pickyourown.org/PYO.php?URL=http%3A%2F%2Fwww.nytimes.com/1993/02/16/science/q-a-133693.html

http://www.inspection.gc.ca/food/information-for-consumers/fact-sheets/specific-products-and-risks/fruits-and-vegetables/natural-toxins/eng/1332276569292/1332276685336

http://extension.illinois.edu/poinsettia/facts.cfm

http://aggie-horticulture.tamu.edu/archives/parsons/flowers/poinsettia.html

http://www.mayoclinic.org/healthy-lifestyle/infant-and-toddler-health/expert-answers/poinsettia-plants/faq-20058304