15 Poisonous Flowers to Avoid and Remove From Your Garden

Flowers are undeniably beautiful, adding color and charm to any garden. However, beneath their attractive appearance, some flowers can be dangerous, harboring toxic substances that pose serious risks.

I’ve compiled a short list of poisonous plants and flowers commonly found in gardens and the effects of exposure to them, from a simple headache to more severe health issues.

Plant Toxicity Levels and Their Effects

Plants generally fall under 4 different toxicity levels, with level 1 as the most severe. This is a general description of the levels and how they interact with the body.

• Dermatitis (Level 4): The thorns, sap, juice, or oils of this plant can cause rashes and irritation when touched. These conditions may be treated by using soap and water to wash the affected areas.
• Oxalates (Level 3): The juice or sap of these plants contain oxalates. Oxalates can cause stomach pain, a burning sensation in the mouth area, breathing difficulties or digestive tract irritation when consumed.
• Minor Toxicity (Level 2): Minor toxicity plants carry symptoms like diarrhea and vomiting after consumption.
• Major Toxicity (Level 1): Some of these plants contain lethal toxins that can cause gastrointestinal or cardiac issues, including fainting, vomiting, diarrhea, numbness and irritation. If you have consumed any of these plants, you will need immediate medical treatment.

I recommend calling your local poison control center should you come into contact with any of these plants.

1. Oleander

• Scientific Name: Nerium oleander
• Other Common Names: Rosebay
• Toxicity Level: Major toxicity (Level 1), Dermatitis (Level 4)
• Dangerous Parts and Components: All plant parts, including the leaves, flowers, stems, and sap, are highly toxic.
• Common Locations: They are commonly found in warm climates in gardens and landscapes in Mediterranean regions, the Southern United States, and parts of Asia.

Oleander is a striking evergreen shrub with long, narrow leaves and clusters of showy, fragrant flowers ranging from white to pink to red.

The effects of poisoning from oleander can be severe and include symptoms such as nausea, vomiting, abdominal pain, and irregular heartbeats.

For some varieties, like the Nerium oleander, consumption of the plant can even lead to death.

2. Foxglove

• Scientific Name: Digitalis purpurea
• Other Common Names: Fairy Gloves, Digitalis
• Toxicity Level: Major toxicity (Level 1)
• Dangerous Parts and Components: The plant’s leaves, flowers, seeds, and roots are all toxic.
• Common Locations: They are commonly found in gardens, woodlands, and meadows, particularly in temperate regions of Europe and North America.

Foxglove is a tall, elegant plant known for its tubular, bell-shaped flowers in shades of purple, pink, white, and yellow. In my experience, it is typically found in garden borders, woodland edges, and wildflower meadows.

The effects of poisoning from Foxglove are severe and potentially life-threatening, with symptoms including nausea, vomiting, diarrhea, abdominal pain, dizziness, confusion, and irregular heartbeats.

3. Lily of the Valley

• Scientific Name: Convallaria majalis
• Toxicity Level: Major toxicity (Level 1), Dermatitis (Level 4)
• Dangerous Parts and Components: All plant parts, including the leaves, flowers, and berries, are toxic. Avoid touching or ingesting any part of the plant.
• Common Locations: They are commonly found in shaded and woodland gardens and naturalized in wooded areas.

Lily of the Valley is a delicate, perennial plant characterized by its tiny, bell-shaped white flowers that dangle gracefully from thin, arching stems.

It thrives in cool, moist soil and provides a lovely ground cover with its lush green foliage.

The effects of poisoning from Lily of the Valley are serious and can include symptoms such as nausea, vomiting, abdominal pain, diarrhea, confusion, drowsiness, and irregular heartbeats.

They also contain toxic chemical compounds like cardiac glycosides, which can result in the abovementioned symptoms. In the worst cases, it can even lead to death.

4. Rhododendron

• Scientific Name: Rhododendron spp.
• Toxicity Level: Major toxicity (Level 1)
• Dangerous Parts and Components: All plant parts, especially the leaves and flowers, are toxic.
• Common Locations: They are commonly found in gardens, parks, and wooded areas in countries such as the United States, the United Kingdom, Japan, China, and Nepal.

Rhododendron is a stunning shrub known for its large, vibrant flower clusters, which bloom in a variety of colors including pink, purple, red, and white.

The effects of poisoning from Rhododendron include symptoms such as nausea, vomiting, drooling, abdominal pain, and difficulty breathing.

5. Azalea

• Scientific Name: Rhododendron spp. (Azalea subgroup)
• Toxicity Level: Major toxicity (Level 1)
• Dangerous Parts and Components: The plant’s parts, especially the leaves and flowers, are toxic. Avoid touching or ingesting any part of the plant.
• Common Locations: They are commonly found in gardens, parks, and wooded areas in the United States, the United Kingdom, Japan, China, and South Korea.

Azaleas are beautiful, flowering shrubs in the Rhododendron family. They are known for their vibrant, colorful blooms, which range from white and pink to red and purple.

The effects of poisoning from Azaleas are severe and include symptoms such as nausea, vomiting, diarrhea, weakness, and difficulty breathing.

6. Castor Bean

• Scientific Name: Ricinus communis
• Other Common Names: Castor Oil Plant, Palma Christi
• Toxicity Level: Major toxicity (Level 1)
• Dangerous Parts and Components: The plant’s parts, especially the seeds, are highly toxic. Avoid touching or ingesting any part of the plant.
• Common Locations: They are commonly found in tropical and subtropical regions, often cultivated in gardens and landscapes for their ornamental foliage.

Castor Bean is a striking plant known for its large, lobed leaves and spiky seed pods, which add a dramatic touch to any garden.

They are often cultivated in gardens and landscapes for their ornamental foliage and in commercial settings for castor oil production.

The effects of poisoning from Castor Bean are extremely severe and can include symptoms such as nausea, vomiting, diarrhea, abdominal pain, and severe dehydration.

The seeds are particularly dangerous, as they contain ricin, a potent toxin that can cause organ failure and death if ingested, making this plant extremely hazardous to humans and animals.

7. Poison Oak

• Scientific Name: Toxicodendron diversilobum (Western Poison Oak) or Toxicodendron pubescens (Eastern Poison Oak)
• Toxicity Level: Dermatitis (Level 4)
• Dangerous Parts and Components: The leaves, stems, and roots of the plant contain urushiol oil, which can cause severe skin irritation. Avoid touching any part of the plant.
• Common Locations: They are commonly found in wooded areas, along trails, and open fields in the United States, particularly in the western and southeastern regions. It is also found in some parts of Canada.

Poison oak is a shrub or vine with leaves and three leaflets, which can be smooth, lobed, or toothed and change color with the seasons.

If you’ve ever heard the warning, “leaves of three, let it be,” poison oak falls under that classification, along with poison ivy.

Contact with poison oak causes severe skin irritation characterized by itching, redness, swelling, and blistering. All parts of the plant contain urushiol oil, which causes these reactions upon contact.

Touching the plant can result in a painful, itchy skin rash that can spread if the oil is not promptly and thoroughly washed off.

8. Nightshade

• Scientific Name: Atropa belladonna
• Other Common Names: Deadly Nightshade, Belladonna
• Toxicity Level: Major toxicity (Level 1)
• Dangerous Parts and Components: The plant’s parts, particularly the berries and roots, are highly toxic. Avoid touching or ingesting any part of the plant.
• Common Locations: They are commonly found in wooded and uncultivated areas, particularly Europe, North Africa, and Western Asia.

Nightshade is a perennial herbaceous plant with dark green leaves, bell-shaped purple flowers, and shiny black berries. Due to its historical and medicinal associations, I’ve occasionally seen it in gardens as an ornamental plant.

The effects of poisoning from nightshade are severe and can include symptoms such as dilated pupils, sensitivity to light, blurred vision, headaches, confusion, convulsions, and hallucinations.

Ingesting any part of the plant, especially the berries and roots, can lead to potentially fatal outcomes, making this plant extremely dangerous to both humans and animals.

9. Hemlock

• Scientific Name: Conium maculatum
• Other Common Names: Poison Hemlock, Water Hemlock
• Toxicity Level: Major toxicity (Level 1)
• Dangerous Parts and Components: The plant’s leaves, stems, roots, and seeds are all highly toxic.
• Common Locations: They are commonly found in damp areas such as riverbanks, ditches, marshes, and roadsides, particularly in Europe, North America, and parts of Asia. It can also appear in fields and open areas.

Hemlock is a tall, biennial plant with smooth, hollow stems usually spotted or streaked with purple. It has finely divided, fern-like leaves and small white flowers arranged in umbrella-shaped clusters.

I’ve typically found Hemlock in damp areas such as riverbanks, ditches, and roadsides.

The effects of poisoning from Hemlock are extremely severe and can include symptoms such as nausea, vomiting, abdominal pain, trembling, muscle weakness, and respiratory failure.

10. Jimson Weed

• Scientific Name: Datura stramonium
• Other Common Names: Devil’s Trumpet, Thorn Apple
• Toxicity Level: Major toxicity (Level 1)
• Dangerous Parts and Components: The plant’s parts, particularly the seeds and leaves, are highly toxic. Avoid touching or ingesting any part of the plant.
• Common Locations: They are commonly found in fields, pastures, roadsides, and waste areas, particularly in North America, but also in Europe, Asia, and Africa.

Jimson Weed is a large, annual plant with distinctive trumpet-shaped white or purple flowers and spiky seed pods. It often grows in disturbed soils and becomes a weed in agriculture.

The effects of poisoning from Jimson Weed are severe and can include symptoms like dry mouth, thirst, blurred vision, hallucinations, seizures, and elevated body temperature. This plant is highly toxic and can be fatal if ingested.

11. Giant Hogweed

• Scientific Name: Heracleum mantegazzianum
• Toxicity Level: Major toxicity (Level 1)
• Dangerous Parts and Components: The plant’s sap is highly toxic and can cause severe skin irritation and burns.
• Common Locations: They are commonly found in fields, along riverbanks, roadsides, and waste areas, particularly in Europe and North America. It is often found in areas with moist soil and partial shade.

Giant Hogweed is a large, invasive plant known for its impressive height, often reaching up to 14 feet, and its large, umbrella-shaped clusters of white flowers.

The effects of contact with Giant Hogweed are severe and include symptoms such as painful skin irritation, blistering, and burns that can lead to long-term scarring.

The plant’s sap is highly toxic and phototoxic, making it more harmful when exposed to sunlight.

12. Poison Sumac

• Scientific Name: Toxicodendron vernix
• Toxicity Level: Major toxicity (Level 1)
• Dangerous Parts and Components: The plant’s leaves, stems, and roots can cause severe skin irritation.
• Common Locations: They are commonly found in wet, swampy areas, such as bogs and marshes, particularly in the eastern United States and Canada.

Poison sumac is a tall, woody shrub or small tree with pinnate leaves with 7 to 13 leaflets arranged in pairs and clusters of small, greenish flowers that turn into white or gray berries.

I’ve often found these shrubs in wet, swampy areas such as bogs and marshes.

All parts of the plant contain urushiol oil, the same toxic compound found in poison oak, making it highly dangerous upon contact. Its symptoms include severe skin irritation, itching, redness, swelling, and blistering.

13. Daffodil

• Scientific Name: Narcissus spp.
• Toxicity Level: Minor toxicity (Level 2)
• Dangerous Parts and Components: The plant’s parts, particularly the bulbs, are toxic. Avoid ingesting any part of the plant, and handle its bulbs with care to avoid skin irritation.
• Common Locations: They are commonly found in gardens, parks, and landscapes worldwide, particularly in temperate regions of Europe, North America, and Asia.

Daffodils are bright, cheerful yellow flowers that I love for their distinctive trumpet-shaped blooms in shades of yellow, white, and orange. They are popular ornamental plants that herald the arrival of spring.

The effects of daffodil poisoning include nausea, vomiting, abdominal pain, and diarrhea. All parts of the plant, particularly the bulbs, are toxic if ingested.

Handling the bulbs can also cause skin irritation, so I advise handling them with care and avoiding ingestion to prevent any adverse health effects.

14. Rosary Peas

• Scientific Name: Abrus precatorius
• Other Common Names: Jequirity Bean, Crab’s Eye
• Toxicity Level: Major toxicity (Level 1)
• Dangerous Parts and Components: The seeds are highly toxic. Avoid touching or ingesting the seeds, as even a small amount can be fatal.
• Common Locations: Commonly found in tropical and subtropical regions, including parts of Africa, Asia, the Caribbean, and Central and South America.

Rosary Peas are slender, perennial climbers known for their distinctive bright red seeds with a black spot, resembling a ladybug.

Due to their striking appearance, they are often found in fields, forests, and along roadsides and are sometimes used in jewelry and ornamental crafts.

The effects of poisoning from Rosary Peas are extremely severe and can be fatal. The seeds contain a potent toxin called abrin, and ingestion can lead to symptoms such as nausea, vomiting, abdominal pain, diarrhea, and organ failure.

Even handling the seeds can be dangerous if they are damaged, as the toxin can be absorbed through cuts or abrasions in the skin.

15. Wild Parsnip

• Scientific Name: Pastinaca sativa
• Toxicity Level: Major toxicity (Level 1)
• Dangerous Parts and Components: The plant’s sap is toxic and can cause severe skin irritation and burns when exposed to sunlight. Avoid touching the plant, especially the sap.
• Common Locations: They are commonly found in fields, roadsides, and disturbed areas, particularly in North America and Europe.

Like the other members of the carrot family, the wild parsnip is a tall, biennial plant with yellow, umbrella-shaped flower clusters and grooved stems.

They often grow in sunny, open spaces and I’ve discovered they can become invasive if not managed properly.

Contact with wild parsnips can cause severe skin irritation and burns, known as phytophotodermatitis.

The plant’s sap is toxic and, when exposed to sunlight, can cause painful blisters, redness, and long-lasting skin discoloration.

 

Other Guides from Planet Natural:

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19 Types of Wildflowers to Consider Growing (And Why)