OLEANDER

Oleander is a popular ornamental plant prized for its drought tolerance and flowers e.g. Nerium oleander 'Hardy Pink'.

It can be deadly if any part of the plant if ingested, even contact with the foliage can irritate skin.

The toxic chemicals in this plant are Oleandrin and Conessine.

Ingestion causes seizures, an erratic heartbeat and coma.

The leaves contain the most toxins, but they are so exceedingly bitter that it’s difficult to eat them and so poisoning cases are rare.

Scientific name: Nerium oleander
Toxins: CONESSINE C₂₄H₄₀N₂ & OLEANDRIN C₃₂H₄₈O₉
Toxic parts: leaves

“Structure of oleandrin” by Jeff Dahl used under CC BY-SA 3.0

WHITE SNAKE ROOT

White Snakeroot is an herb that grows in America. It has leaves like a strawberry plant and produces clusters of white flowers. 

The killer chemical in this plant is called tremetol.

Consuming milk or meat from animals that have eaten the white snakeroot plant is usually how people get poisoned with Tremetol.

 Fun fact - Abraham Lincoln’s mother-in-law died of milk sickness (drinking tremetol-contaminated cow’s milk).

 Symptoms include a red tongue, high blood acidity and weakness.

A cultivar named Eupatorium rugosum 'Chocolate' can be found in garden stores.

Scientific name: Ageratina altissima
Toxin: TREMETOL C13H14O2
Most toxic parts: Foliage

WATER HEMLOCK 

Water hemlock is difficult to spot out because it looks like Carrots or Parsnips from the top.

The killer chemical in this plant is called cicutoxin.

Cicutoxin is most concentrated in the roots but can be found throughout the plant as well. After consuming the plant people experience cramps, nausea and convulsions.  However even people who do survive have lasting symptoms like amnesia and tremors.

Scientific name: Cicuta douglasii
Toxin: Cicutoxin C17H22O2
Most toxic parts: Roots

CASTOR BEAN

The plant is native to Africa, but people also grow it as an ornamental plant.

The killer compound in this plant is called Ricin and is found mostly in the seeds.

Symptoms of ricin poisoning kick in within 4 to 6 hours and include vomiting, diarrhoea, and seizures. Ricin has been used in multiple assassinations, but most deaths occur in children and pets who accidentally eat the beans.

8 seeds are usually enough to kill an adult male, while it takes just 2 beans to kill a child.

Scientific name: Ricinus communis.

Toxin: Ricin (protein) RCOM_2159910.

Toxic parts: Seeds.

“The ricin (2aai) structure” by AzaToth, used under CC BY 3.0.