Black locus
Colic, depression, 
convulsions.

Black walnut
Laminitis (founder)

Oleander
Diarrhea, colic, irregular heartbeat.
Roadsides, farmyards, plant cutting

Yew
Acute collapse and rapid death.
Ornamental, evergreen shrub, grows as a hedge.

Horsetail

can produce a deficiency of vitamin B. Signs of horsetail intoxication include weakness, decreased appetite, and loss of coordination

Foxglove
Diarrhea, colic, irregular heartbeat.

Lantana
Jaundice, liver failure

Red maple
Loss of appetite, depression, anemia, jaundice.