Hemlock, sometimes referred to as "Spotted Hemlock" has fern-like leaves and white flower clusters. It is toxic to horses, as it contains neurotoxins that can effect both a horse's central and peripheral nervous system.
If a horse has ingested Hemlock, signs can include tremors, anxiety, slowing heart and respiratory rate. The horse can die from respiratory failure, even if the toxicity is caught quickly, so immediate care from an emergency veterinarian is especially important.
There is no specific treatment, other than supportive care, so when ingested in large amounts, Hemlock is usually fatal.