26 Poisonous Plants: Watch Out for These Bad Boys

Poison oak, poison ivy and poison sumac are the obvious culprits, but there are a whole host of dangerous plants out there.

By: Felicia Feaster

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Poison Ivy

Poison Ivy may be number one on everyone's short list of plants to watch out for in the yard. Knowing how to identify poison ivy (Toxicodendron radicans) is critical to steering clear of this plant, which can cause reactions in humans ranging from a red, itchy rash to blistering or even anaphylaxis.

Learn More: How to Kill Poison Ivy in Your Yard

Poison Sumac

The leaves of poison sumac sometimes have black or dark brown spots that are filled with urushiol. In autumn, the leaves turn red, yellow and pinkish. Poison sumac typically grows into a woody shrub with glossy cream or pale yellow berries.

Learn More: Poison Plants: Identifying Poison Ivy, Poison Oak and Poison Sumac

Bleeding Heart

Dicentra spectabilis, or bleeding heart, is native to woodlands and is a shade loving perennial. The name bleeding heart describes the unique flowers, which resemble tiny pink or white hearts with drops of blood at the bottom. The roots and foliage of bleeding heart contain alkaloids that are toxic to people and plants if eaten in large amounts.

Learn More: How to Grow Bleeding Heart

Azalea

All parts of the azalea are dangerous if eaten in great quantities. Ingestion of the toxin contained in the plant, andromedotoxin, can result in progressive paralysis, coma and death. But human fatalities from eating this plant are rare.

Learn More: How to Plant and Grow Azaleas

Poison Oak

One of the potential plant dangers lurking in backyards and forests: poison oak.

English Ivy

English ivy, as seen growing on this tree, is poisonous if eaten in large quantities.

Nerium Oleander Is a Deadly Beauty

Nerium oleander is a rounded shrub or small tree, with long, dark green leaves and an abundance of single or double, sometimes fragrant flowers in variety of colors. All parts of the plant are extremely poisonous.

Learn More: Oleander: Pretty But Poisonous

Heartleaf Philodendron

All parts of the philodendron are toxic.

Learn More: Philodendron Care

Narcissus

The entire daffodil is poisonous, but especially the bulb.

Learn More: Planting and Growing Daffodils

Dieffenbachia Amonena

Also known as dumb cane, this houseplant is poisonous and dangerous for humans and animals.

Iris

The rhizomes and root stock of the iris are poisonous.

Learn More: Iris Flower: Varieties to Grow and How to Care for Them

Foxglove

The flowers, leaves, stems and seeds of foxglove are poisonous.

Learn More: How to Grow Foxgloves

Mistletoe

This traditional holiday decoration also contains hazardous viscotoxins, with the berries being particularly dangerous.

'Silver Queen' Euonymus Fortunei

All parts of this evergreen can cause vomiting, diarrhea, coma and convulsions if ingested.

Aloe

Aloe can cause digestive distress when ingested.

Amaryllis

The amaryllis bulb contains the poisonous alkaloid lycorine, harmful to pets and humans.

Learn More: How to Grow and Care For Amaryllis

Chrysanthemum

Chrysanthemum is toxic to animals.

Begonia

Begonia is toxic to dogs and cats, according to the ASPCA.

Caladium

Caladium is poisonous to pets.

Gardenia

Both the leaves and flowers of the gardenia are toxic to dogs, cats and horses. Ingesting those parts of the shrub can lead to hives, vomiting and diarrhea in those animals, though the gardenia is not considered toxic to humans.

Hibiscus

Hibiscus is toxic to dogs, cats and horses, according to the ASPCA.

Lily of the Valley

All parts of the plant and berries are highly poisonous.

Giant Hogweed

Heracleum mantegazzianum, also known as giant hogweed, is one nasty character. This invasive species can grow up to 14 feet tall. Contact with the plant's sap can cause severe skin and eye irritation and even blindness. Exposure to this biennial or perennial noxious herb can even result in scarring. In a nutshell: stay away!

Castor Oil Plant

The castor oil plant, Ricinus communis, is a very useful tropical foliage plant. It is grown from seed, easily reaching more than 10 feet in one season. The plant has big leaves, grows very tall and produces tons of seeds, which are toxic.

Euphorbia

Euphorbia schillingii can cause bad skin irritations if touched with bare skin.

Wolfsbane

Aconitum vulparia, commonly known as wolfsbane, bears ivory to yellowish flowers from late spring into autumn. Aconitums are extremely poisonous and can cause numbness and tingling just by brushing against the plants.