Sheep-laurel-Kalmia angustifolia L.-Poisonous plant

Sheep-laurel

General poisoning notes:

Sheep-laurel (Kalmia angustifolia) is a native shrub found in eastern Canada in boggy areas. This plant contains a toxin that has poisoned cattle, goats, and sheep as well as humans. Poisoning rarely happens in the wild. Other animals have been poisoned by sheep-laurel, including zebras at a zoo, as well as horses. Meat of chickens that had ingested sheep-laurel may be toxic to other animals. The nectar contains the toxin that results in toxic honey (Marsh 1930, Kingsbury 1964, Verlangieri 1976, Lampe and McCann 1985).

Description

Shrubs erect, 0.3-1.5 m. Twigs terete, viscid, glabrous or puberulent. Leaves usually in whorls of 3, rarely alternate or opposite; petiole 6-16 mm, usually puberulent; blade oblong to elliptic-lanceolate, 1.5-8 × 0.5-2.5 cm, margins usually plane, apex obtuse to acute, usually apiculate, abaxial surface glabrous or puberulent, sometimes stipitate-glandular, adaxial lightly puberulent (hairs white, to 0.1 mm), sometimes glabrescent, midrib puberulent. Inflorescences axillary near distal end, corymbiform racemes, 4-12-flowered. Pedicels 5-20 mm. Flowers: sepals usually green, sometimes reddish apically or throughout, ovate, 2-2.8 mm, apex usually acuminate, surfaces puberulent; petals connate nearly their entire lengths, usually reddish purple to pink, rarely white or bluish pink, usually deeper colored near anther pockets and with ring of red to purple spots just proximal to pockets, 7.5-9.5 × 6-13 mm, abaxial surface puberulent, adaxial glabrous, puberulent toward base; filaments 2.5-3.5 mm; style 3.5-4.5 mm. Capsules 5-locular, 2-3.5 × 3-5 mm, puberulent, stipitate-glandular. Seeds winged, obovoid, 0.6-1 mm. 2n = 24.

Nomenclature:

Scientific Name: Kalmia angustifolia L.

Vernacular name(s): sheep-laurel

Scientific family name: Ericaceae

Vernacular family name: heath  

Geographic Information

New Brunswick, Newfoundland, Nova Scotia, Ontario, Prince Edward Island, Quebec.

Notes on Poisonous plant parts:

The entire plant is poisonous, including the nectar and honey made from it (Pritchard 1956, Kingsbury 1964).

Toxic parts:

All parts, flowers,leaves, mature fruit, stems.

Notes on Toxic plant chemicals:

Andromedotoxin and resins derived from diterpenes are the toxic compounds found in all the toxic species of the heath plant family. The toxin is found even in the nectar of flowers (Fuller and McClintock 1986). Experimental poisoning of rats using leaf extracts resulted in an average LD-50 (female) of 8.2 g of green leaves per kilogram body weight. The leaves were toxic only in the spring. Leaves of plants growing in wet areas were more toxic than those growing in dry areas (Verlangieri et al. 1976).

Toxic plant chemicals:

Andromedotoxins

Chemical diagram(s) are courtesy of Ruth McDiarmid, Biochemistry Technician, Kamloops Range Station, Agriculture and Agri-Food Canada, Kamploops, British Columbia, Canada.

Animals/Human Poisoning:

Note: When an animal is listed without additional information, the literature (as of 1993) contained no detailed explanation.

Cattle

General symptoms of poisoning:

breathing, shallow

diarrhea

gait, staggering

incoordination

recumbency

salivation

vomiting

Notes on poisoning:

Experimental poisoning of cattle showed symptoms, including soft feces, salivation, vomiting, diarrhea, and incoordination. Consuming green leaves equivalent to 0.2% of an animal''s body weight was determined to cause toxic signs in cattle (Marsh 1930). A few cattle in the field were poisoned after ingesting sheep-laurel (Kingsbury 1964).

Goats

General symptoms of poisoning:

Incoordination, recumbency, vomiting, weakness.

Notes on poisoning:

Experimental poisoning of goats fed green leaves resulted in symptoms, including profuse vomiting, staggering, recumbency, weakness, shallow breath, and teeth grinding. Sheep-laurel causes toxic signs in goats if ingested green material equaled at least 0.25% of animal body weight (Marsh 1930).

Humans

General symptoms of poisoning:

Coma.

Rodents

General symptoms of poisoning:

Coma, convulsions, death, nasal discharge, paralysis, salivation, vomiting.

Sheep

General symptoms of poisoning:

Ataxia, coma, convulsions, death, depression, dyspnea, headache, nasal discharge, pupil dilation, recumbency, salivation, vomiting.

Notes on poisoning:

Experimental poisoning of a goat caused symptoms of poisoning similar to those seen in sheep. A dosage of green leaves equal to 0.5% of an animal''s body weight caused symptoms to occur (Clawson 1933).