Toxic Parts:
cyanogenic glucosides irritants injury
Flower Color:
  • flower color
woodlands, meadows, ornamental

Time of Greatest Risk


Geographical Distribution

Blackthorn distribution - United States

Related Species


Prunus spinosa

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Blackthorn (Prunus spinosa) is a deciduous flowering shrub or small tree that is known for its sharp spines or thorns. It belongs to the same genus (Prunus) as cherry, plum, peach, apricot and almond trees. Blackthorn is most commonly found in hedgerows and thickets, forming dense stands of thorns.

Blackthorn flowers early, between March and April, and the seeds ripen in October. It produces five-petaled white flowers and dark round bluish purple berries. Each berry contains a large stone with a single seed inside.

Blackthorn Toxic Components

Being a member of the Prunus family, Blackthorn contains varying amounts of cyanogenic glycosides---which convert to cyanide (prussic acid) when plant parts are chewed, crushed, trampled, or grinded. Cyanide is a highly toxic poison, which is quickly absorbed from the gastrointestinal tract into the bloodstream. Once in the blood, it inhibits the blood cells from delivering oxygen to tissue cells causing the horse's blood to become supersaturated with oxygen and appear bright red. Depending on how much cyanide is ingested, horses may develop signs of acute poisoning or chronic poisoning. The toxin is found predominately in the leaves and seeds of this plant.

Blackthorn is also known for causing infections and tissue reactions in horses, due its sharp thorns. The resulting condition is referred to medically as blackthorn plant thorn synovitis.