April 25, 2017



Infernal spring trio: Lily of the valley (Convallaria majalis), wild garlic (Allium ursinum) and autumn crocus (Colchicum autumnale)

As kids, we were warned not to mistake wild garlic for lily of the valley, which is actually rather difficult to accomplish since both plants have their own peculiar odour. Early spring forests reek of garlic long before any lily sprouts! What might prove more fatal is confusing wild garlic with meadow saffron, also called autumn crocus. This bulb flowers only in autumn, so only its leaves are visible in spring and these also look rather similar to wild garlic ones, if not for the latter’s distinct odour. The nose is the best organ to prevent accidental poisoning in real life. In a crime novel, the trio of spring plants might give rise to an infernally devious murder plot.

English version

049 Of the three, wild garlic is the least toxic. For humans at least. It makes an excellent addition to any salad, soup or pesto sauce. But woe if the dog finishes off the soup, it might finish him off for good! Wild garlic, as well as garden garlic and onion, contains organic sulfides like N-Propyl-Disulfide and Sodium-Propyl-Thiosulfate which are not only responsible for the typical garlic odour but they irritate mucous membranes locally, resulting in vomiting and diarrhoea. Further, these sulfates damage red blood cells by destroying the oxygen transporting protein haemoglobin, leading to anaemia - at least in dogs, horses and cattle. These animals also develop symptoms like bloody urine, pale mucous membranes, jaundice and ataxia. Humans are protected from garlic’s poisonous contents by a special enzyme.

The second most poisonous of the trio is lily of the valley. Its active ingredients have a similar pattern of action as foxglove: it contains a series of heart glycosides like convallatoxin, convallosid and convallamarin, a series of saponines like convallarin, convallaric acid that act as laxatives, as well as the toxic amino acid acetidine carbonic acid. The result of eating lily of the valley is vomiting and diarrhoea with slowed and irregular pulse, but contrary to foxglove, resorption of lily of the valley glycosides in the digestive tract is poor. The berries that appear in summer have proven not to be very toxic. There has been no fatal case of lily of the valley poisoning though during the last 40 years, neither in Switzerland nor in the USA. In the States, with 2639 cases of ingestion of any part of lily of the valley on record, only three patients have developed serious symptoms: excess salivation, headache, hallucinations, cold, clammy skin, vomiting, diarrhoea, cardiac arrhythmias, bradycardia, dyspnoea, cramps. Death can occur through heart failure.

049 Autumn crocus is definitely the most poisonous of the trio. Named after Kolchis, the region between the eastern shores of the Black Sea and the Caucasus mountains, the home of the mythical enchantress Medea, it contains a toxic cocktail of alkaloids like colchicin, colchicosid and demecolcin. Alkaloid contents is varying between 0.1-2.0%, i.e. in seeds 0.5-1.2%, in flowers 1.2-2.0%, in leaves 0.15-0.4%, and in bulbs 0.1-0.6%. The older the leaves or flowers, the higher the contents, but alkaloid contents decreases with higher altitudes. Colchicin inhibits mitosis, i.e. the propagation of living cells by cell division, therefore it has its strongest effects on tissues with a high cell division rate, like mucous membranes. It is taken up by the body very quickly. In Switzerland since 1966, four poisonings with autumn crocus ended fatally, thirteen more with heavy symptoms. Symptoms of autumn crocus poisoning are: colic, salivation, apathy, unsteady motion, grinding of teeth, vomiting, yellowish-green, greenish-slimy or bloody diarrhoea, polyuria (intense and frequent urination), bloody urine, anuria (no urination), stop of milk flow, cardiac and circulatory disturbances, hypothermia, paralysis, death through circulatory and / or respiratory failure.

Reaction time

  • Wild garlic: One to several days after ingestion (in dogs and cats – not poisonous to humans).
  • Lily of the valley: Onset immediately or after 15 – 20 min.
  • Autumns crocus: Latency 2-48 hours. Death can occur 1-3 days (until 7 days) through respiratory paralysis (lethality 25 – 50%).

Toxic doses

  • Wild garlic: 2-5g bulbs/ kg body weight for dogs, cattle, horses.
  • Lily of the valley: No orl doses available. Rat (intravenuously): 38 mg/kg convallatoxin, mouse (subcutaneous) 70 mg/kg convallarine, LD50 cat (intravenously): 0.07-0.08 mg/kg convallatoxin.
  • Autumn crocus: Oral doses only! Lethal dosis1 mg/kg body weight pure Colchicin, heavy diarrhoea already from 0.25 mg/kg body weight.

  • Cattle and horses: 8-16 g/kg body weight or 1200-1500 g of per animal if fresh leaves are taken, equals 2-3 g/kg body weight or 200-250 g per animal of dried plant parts.
  • Pigs: 30 g/100 kg body weight fresh onions.
  • Lambs: 6.4 g/kg body weight fresh leaves.


Drying or cooking does not reduce toxicity of wild garlic (for dogs or cats), lily of the valley or autumn crocus! The active ingredient of autumn crocus, cholchicin, can also be excreted via milk, i.e. cows that have consumed autumn crocus, but are symptomless, can poison their calves and/ or milk consumers, leading to secondary poisonings. Ruminants like cows can develop resistance against autumn crocus poison, not so horses or pigs.

049© Swiss Toxicology Center / Schweizer Toxikologiezentrum


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Eva Waiblinger


Eva Waiblinger, MSc, PhD (Dr. sc. nat.), is a Swiss zoologist and science journalist as well as a member of the Swiss National Ethics Committee for Animal Experiments. She currently works as a Math and Biology teacher at a vocational school. Before that, she has been head of the companion animal welfare department of Swiss Animal Protection SAP for 12 years. She currently writes a biomedical thriller. The remainder of her leisure time is taken up by Goju Ryu karate and the all-female vocal ensemble Qtet she founded.