Toxic flowers include wisteria, hydrangea, foxglove and lily-of-the-valley. Every part of the oleander is toxic, and poisonous berries grow on mistletoe and nightshade plants. Moonseed, which produces berries that appear similar to grapes, are also toxic. Yew, cherry and oak trees are toxic, and the elderberry tree contains a toxin similar to cyanide. Like the elderberry tree, the twigs and foliage of the cherry tree contain a cyanide-like toxin. Acorns are toxic when consumed in large quantities.
Castor beans and rosary peas are among the most toxic plants. Consuming even one castor bean or rosary pea can cause death. Rhubarb leaves are toxic when consumed, and many common flowers, such as chrysanthemums, daffodils and daisies, contain toxins.
Some flowers, such as aconite and monkshood, are very toxic and can cause serious symptoms if any part of the flower is consumed. Consuming the foliage or seeds of the yew tree can cause sudden death, and all parts of the lantana are toxic when consumed. Some plants, such as chamomile, croton and balsam fir, cause skin irritation or rash.
Mayapples contain several poisonous compounds, and eating the apples often causes digestive upset. Apple and crabapple seeds are toxic, and they can be fatal when eaten in large quantities. Hemlock is one of the most famous toxic plants. Eating any part of the hemlock can be fatal.