Most species of crocus are poisonous. The only safe species are Crocus Vernus (Dutch Crocus and Spring Crocus).
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Colchicum species
Common Names: Crocus, Autumn Crocus, Fall Crocus,
Meadow Saffron, Mysteria, Vellorita, Wonder Bulb.
Description: Tubular purple or white flowers which emerge from
the underground bulb.
Toxic Part: Whole plant is very poisonous.
Symptoms: Upon ingestion, immediate burning
pain in mouth and throat with
intense thirst followed by nausea,
vomiting, and diarrhea. Less than
one flower can be deadly.
Also Prarie Crocus and Wild Crocus are poisonous.