Creeping buttercup can be severely toxic to dogs; you should seek immediate veterinary attention if you believe your dog has eaten or come into contact with a plant of this type. All parts of these plants contain ranunculin, a toxin that is poisonous when swallowed and also can irritate skin, causing redness or itch. Ingestion symptoms ranging from excessive drooling, vomiting, diarrhea, weakness, and loss of appetite to paralysis, seizures, jaundice, spasms, collapse, or even death.

All parts of common columbine, including the stem, leaves, flowers, and seeds, are toxic when they are ingested raw. Contact with the plant's sap may also lead to dermatitis (skin irritation and inflammation). The symptoms from common columbine poisoning are likely to cause only mild to moderate effects, but the symptoms are not well-known, since there are few documented cases of it. Adverse effects are most likely to occur from accidental ingestion.

Cow parsnip (Heracleum sphondylium) is a species of flowering perennial herb related to parsley and fennel. Its specific epithet, "sphondylium," means "vertebrate," and references its segmented appearance. This species produces extremely large amounts of nectar and thus attracts many bees.

Sun spurge (Euphorbia helioscopia) is a winter annual that grows along the ground in a variety of locations from gardens to wastelands. It features distinctive red colored stems with toothed leaves that emit a toxic milky sap when cut or torn. Pale yellow flowers bloom from spring to summer and give way to fruit. This plant is considered a weed.

All parts of the evergreen spindle are considered toxic if ingested in large quantities. Symptoms can range from mild to life-threatening including vomiting, weakness, diarrhea, chills, convulsions, and coma. Since these plants are commonly used as ornamental hedges, you should be mindful of any children who may encounter the plant, be attracted by its colorful leaves and flowers, and may be tempted to eat them.

Woodland horsetail (Equisetum sylvaticum) is a perennial plant species native to North America and Eurasia. Woodland horsetail grows in swampy forest, open woodlands, and meadow areas. This species is considered one of the most attractive species of horsetail.

Greater creeping spearwort can be severely toxic to dogs; you should seek immediate veterinary attention if you believe your dog has eaten or come into contact with a plant of this type. All parts of these plants contain ranunculin, a toxin that is poisonous when swallowed and also can irritate skin, causing redness or itch. Ingestion symptoms ranging from excessive drooling, vomiting, diarrhea, weakness, and loss of appetite to paralysis, seizures, jaundice, spasms, collapse, or even death.

Smoketree is a deciduous tree native to Southern Europe and Central China. The flowers of the smoketree are pinkish-purple and long-lasting. They grow in clusters along branches and give a smoky appearance to the tree when in bloom. In China, they are used as important fall decorations due to their foliage turn bright red in the fall.

A garden poppy that can escape as a scrambling weed across open fields, the common fumitory (Fumaria officinalis) produces flowers from early spring to late fall. In the past, it had been used as a folk medicine, but it is now known to be poisonous and should not be used in any home remedies.

If either ingested or touched, dieffenbachia can cause negative reactions. The symptoms range from moderate to severe and can be dangerous if airways are blocked. Due to the calcium oxalate contained in this plant, its leaves and sap have toxic properties. When ingested, they can induce symptoms such as lip and tongue swelling, drooling, speech loss, and difficulty breathing; when touched, they can cause a painful skin rash or eye irritation. Since these plants are often found indoors as decorative plants, be careful when keeping them around small children. Always wear gloves when handling this plant.

Hairy willowherb (Epilobium hirsutum) is a species of weed that is difficult to eradicate. It is not known to be toxic, but the sale of this plant or its seeds has been banned in some areas. This is because its dense, aggressive growth habits can crowd out and destroy other native beneficial plants.

The Daphne mezereum is a deciduous shrub that can grow up to 1.5 m tall. Its leaves are soft, spirally arranged on the stems. The february daphne produces a bright red berry as the fruit which is extremely poisonous for humans.

Hyacinthus orientalis is one of the heralds of spring. The name common hyacinth comes from the Greek name Hyacinthus. According to Greek legend, Hyacinthus was admired by both Apollo and Zephyrus. Hyacinthus ended up being killed out of jealousy and a flower bloomed on the spot where his blood was spilled. Apollo named the flower after his lost love.

Common yew is highly toxic to all animal species, including humans, dogs, cats, livestock and poultry, with all parts of the plant capable of causing death when consumed in large amounts.

Striped barbados lily is perennial herbs with showy flowers but it contains toxic compounds, most notably alkaloids lycorine and tazetine, as well as calcium oxalate crystals.

Wild daffodils have low-level toxicity when the leaves or bulbs are ingested. The bulbs, however, are the most toxic part of the plant. If the bulbs are ingested, symptoms may include vomiting, diarrhea, and excessive salivation. If a large quantity is consumed, convulsions, low blood pressure, tremors, and cardiac arrhythmias may occur. Poisoning is most likely to occur from accidental ingestion by children, as wild daffodils are grown in gardens around the world.

Old man's beard (Clematis vitalba) is a deciduous climbing shrub that will grow to 12 m tall. It blooms with fluffy flowers and fruits that have long silky strands that look like the wispy beard of an old man. This plant is a food source for a variety of moths. Often seen scrambling over hedgerows, it is considered a noxious weed, especially in New Zealand. Evidence suggests ancient Europeans made rope and baskets with old man's beard.

Durian (Durio zibethinus) is a tropical plant from Southeast Asia. It bears large, spiny, edible fruit which has become a major export crop of the region. The fruit is best known for its pungent smell, which provokes opposing reactions, ranging from near-addiction to revulsion. In some areas, it has even been banned from public transport and hotels.

Bird of paradise is generally considered non-toxic but can be poisonous when ingested in large quantities. Cases of poisoning are typically mild to moderate with symptoms including abdominal cramps, nausea, vomiting, and diarrhea. Cases of poisoning may be more serious in children. The fruit and seeds are considered to be the most toxic parts of the plant. The frequent use of this plant as a houseplant could be a factor in poisoning frequency. This plant can be mistaken for another more toxic species, Poinciana gilliesii, as they share the same common name, bird of paradise.

Evergreen azalea are members of the Rhododendron genus, all of which contain varying levels of a toxin known as Grayanotoxin in all tissues. Physical contact can cause a rash in sensitive people, the pollen can irritate mucus membranes, and ingesting it can cause nausea, vomiting, arrhythmia, low blood pressure, and hallucinations in humans. Grayanotoxin is so strong that even the amounts contained in honey made from Rhododendron pollen can have negative effects.