Florida Hemlock (Cicuta maculata) Wekiva River, May 2020

Spectacular fields of Florida Hemlock (Cicuta maculata) are in bloom across Central Florida in and near rivers and swamps. This carrot family plant is also referred to simply as "hemlock" or by the common names spotted water hemlock, spotted parsley, spotted cowbane, or suicide root.

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Florida Hemlock (Cicuta maculata), Wekiva River, May 2020

The Wekiva River hosts hundreds of thousands acres of hemlock on the river's floating Eelgrass islands. The plants are anchored to the Eelgrass in shallow portions of the river so they are not really growing on anything but a floating mat of vegetation.

Hemlock (Cicuta maculata)

North America's Most Toxic Plant

Florida Hemlock is one of the most toxic plants known to man. The plant is occasionally mistaken for parsnips, due to its clusters of white tuberous roots; this would be a fatal error, as Florida Hemlock is extremely poisonous. This is the most toxic plant found in North America.

The primary poison in Florida Hemolock is cicutoxin, an unsaturated aliphatic alcohol that is most concentrated in the plant's roots. Upon human consumption, nausea, vomiting, and tremors occur within 30-60 minutes, followed by severe cramps, projectile vomiting, and convulsions. Ingestion of Florida Hemlock in any quantity can result in death or permanent damage to the central nervous system.

Hemlock (Cicuta maculata), North America's Most Toxic Plant

All parts of Florida hemlock are extremely poisonous. The plant is closely related to the hemlock used to execute Socrates.

Hemlock in the Wekiva River, June 2020

n the Wekiva River, where these images were made, the plants are large, highly branched and grow to 8-feet tall in what could best be described as wet meadows of floating mats of vegetation. Throughout the Wekiva the wet meadows are bisected by alligator trails, and one can hear a constant grunting or croaking of alligators coming from the dense fields of Florida Hemlock.

Hemlock, Wekiva River, June 2020.  Sometimes the plant's stems and roots exhibit a purplish color.

Some of the plants in the Wekiva take on a rusty look to their stalks with purple or purple striped stalks. Presumably the purple colored plants are anchored in more muck than Eelgrass and thus they ingest some of the tannins of the mucky river bottom (above).

Wekiva River Florida Hemlock, June 2020

Water hemlock occurs throughout Florida and flowers primarily late April to July (spring and summer).

Hemlock lines an alligator trail in the Wekiva River, Florida, June 2020

The plant produces large, dome-shaped umbels of flowers. An umbel is made of many small flowers that are all attached, more or less at the same point. The flowers are tiny, white, and have 5 petals. The flower umbels are in long stalks that grow from leaf axels at the tips of the stems.

Florida Hemlock

The leaves of Florida Hemlock are large and double- or triple-compound. A triple-compound leaf has leaflets that make up larger leaflets, that make upeven larger leaflets, that make up an entire large leaf. These compound leaves are often a foot or more long and 2 feet wide. The compound leaves are arranged alternately on the stem.

Florida Hemlock, Wekiva River, June 2020

Leaflets of water Florida Hemlock are lance-shaped and have coarse teeth around their margins.

Hemlock, Florida, June 2020

The stem is fleshy and hollow. It may have purple stripes (above) but most of the plants in the Wekiva are green-stalked.

Hemlock, Lower Wekiva River Preserve, June 2020

While many species of aquatic plants are considered edible and have white flowers. This is not an edible plant! Florida Hemlock is extremely toxic to humans and animals and could cause death if ingested.

Hemlock, Wekiva River Florida, June 2020

In Florida, in general it is best to avoid all plants near water with clusters of white flowers. Florida Hemlock is easily confused with less toxic plants with similar blooms like Elderberry. If you don't know for sure, leave it alone.