Grayanotoxins are produced by plants in the family
Ericaceae, specifically members of the
genera Agarista,
Craibiodendron,
Kalmia,
Leucothoe,
Lyonia,
Pieris and
Rhododendron.<a href="
https://en.wikipedia.org/wiki/Grayanotoxin#cite_note-Jansen-2012-3"><span>[</span>3<span>]</span></a><a href="
https://en.wikipedia.org/wiki/Grayanotoxin#cite_note-EFSA_CONTAM_Panel-2023-7"><span>[</span>7<span>]</span></a> The genus
Rhododendron alone encompasses over 750 species that grow around the world in parts of Europe, North America, Japan, Nepal and Turkey. They can grow at a variety of altitudes, ranging from sea level to more than 3 kilometres (9,800 ft).<a href="
https://en.wikipedia.org/wiki/Grayanotoxin#cite_note-Sahin-2015-6"><span>[</span>6<span>]</span></a> While many of these species contain grayanotoxins, only a few contain significant levels. Species with high concentrations of grayanotoxins, such as
R. ponticum and
R. luteum, are most commonly found in regions of Turkey bordering the
Black Sea, and in Nepal.<a href="
https://en.wikipedia.org/wiki/Grayanotoxin#cite_note-gunduz-5"><span>[</span>5<span>]</span></a>
Rhododendron ponticum
Nearly all parts of grayanotoxin-producing rhododendrons contain the molecule, including the stem, leaves, flower, pollen and nectar. Grayanotoxins can also be found in secondary plant products, such as honey,
labrador tea, cigarettes, and herbal medicines.<a href="
https://en.wikipedia.org/wiki/Grayanotoxin#cite_note-Jansen-2012-3"><span>[</span>3<span>]</span></a>
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