Many yards and wild areas are dotted with pretty clusters of small white flowers, especially in late summer and fall. At first glance, they look harmless—just another wildflower adding brightness to the landscape. But behind their beauty, White Snakeroot (Ageratina altissima) hides a dangerous secret: it is toxic to both people and animals. Knowing how to recognize and handle this plant can prevent serious health risks.
What Is White Snakeroot?
White Snakeroot is a perennial plant native to North America. It belongs to the daisy family (Asteraceae) and is often found in:
- Wooded areas
- Roadsides
- Shaded yards
- Pastures
It grows between 1 to 4 feet tall, with thin, smooth stems and clusters of fluffy, small, white flower heads that bloom from late summer into fall. Its seeds spread easily, which is why it shows up in many backyards and fields without being planted.
How to Recognize White Snakeroot
For beginners, recognizing White Snakeroot is important because it looks similar to harmless wildflowers. Here are the key features:
- Leaves: Opposite, rounded or heart-shaped, with serrated (toothed) edges and pointed tips. They are about 3–5 inches long.
- Flowers: Small, white, and fluffy, growing in flat-topped clusters. They bloom from August through October.
- Stems: Smooth, green to sometimes slightly purple, upright, and branched near the top.
- Habitat: Prefers partial shade and moist soil, often found along forest edges and in pastures.
A common mistake is confusing it with boneset (Eupatorium perfoliatum) or other non-toxic wildflowers, but White Snakeroot is shorter and its leaves are not joined around the stem.
Why Is White Snakeroot Dangerous?
White Snakeroot contains a toxic compound called tremetol. When ingested, this toxin can cause a condition known as “milk sickness” in humans. This happens when cows eat the plant and the tremetol passes into their milk, which people then consume.
Historically, milk sickness was a serious problem in the 1800s, especially among settlers. It even caused the death of Nancy Hanks Lincoln, the mother of U.S. President Abraham Lincoln.
Symptoms of Tremetol Poisoning in Humans
If someone ingests White Snakeroot directly—or drinks contaminated milk—the following symptoms may appear:
- Nausea and vomiting
- Weakness and fatigue
- Trembling or muscle stiffness
- Abdominal pain
- Severe cases: organ damage or even death
Toxic to Pets and Livestock
Cows, goats, sheep, and horses are especially at risk, but dogs and cats can also suffer if they chew on the leaves or stems. Symptoms in animals may include:
- Loss of appetite
- Muscle weakness and trembling
- Lethargy
- Difficulty breathing
